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Instrumented Charpy test data have often been used to obtain estimates of various mechanical properties under elevated loading rates, such as dynamic yield properties. A widely used relationship between Charpy general yield force and dynamic yield strength was originally proposed by Server in 1978. This same relationship, however, cannot be used for estimating the dynamic (ultimate) tensile strength from the Charpy maximum force, since it relies on the ratio between shear and tensile stress, which at general yield is different than at maximum force. In the study described in this paper, we modified Server's relationship in order to obtain reliable, and possibly conservative, estimates of dynamic ultimate tensile strength from the maximum force measured in an instrumented Charpy test. Once more experimental data has been accumulated, the results of this investigation might have significant implications for the revision of fracture mechanics test standards which utilize dynamic ultimate tensile properties for the qualification/validation of fracture toughness tests conducted at elevated loading rates. [ABSTRACT FROM AUTHOR]

Abstract: Many studies have demonstrated a relationship between secondary dendrite arm spacing (SDAS) and the mechanical behaviour of cast aluminium–silicon alloys, both for tensile and fatigue strength. SDAS is related to the solidification time and can be predicted, with a good approximation, by finite-element simulation. However, other microstructural features can affect the tensile behaviour of cast aluminium alloys such as size and morphology of the eutectic Si particles, grain size, composition and morphology of the intermetallic compounds. The present investigation was aimed at finding valuable relationships between ultimate tensile strength and the previously mentioned microstructural parameters for the sand cast A357 aluminium alloy. The microstructural characterization was carried out by optical microscopy and image analysis on more than about 2500 micrographs. Starting from the microstructural parameters and taking into account the material hardness, a relationship able to predict the ultimate tensile strength of the alloy, with an error less than 5%, was found. This relationship can be used to evaluate the local values of the UTS in complex cast components knowing only the hardness and the microstructural parameters, even in positions where the extraction of tensile specimens is not possible. [Copyright &y& Elsevier]

[Display omitted] • A non-toxic Zn-0.8Li-0.4Mn alloy is designed and prepared. The synergistic enhancement of strength and plasticity of Zn-0.4Mn-0.8Li alloy is achieved through hot rolling, with an ultimate tensile strength of 449.1 MPa and an elongation rate exceeding 75%. • A correlation between alloy deformation and the corrosion mechanism of Zn-0.4Mn-0.8Li alloys is revealed. The application of biodegradable Zn-based vascular alloy stents proves to be an ideal solution for addressing cardiovascular diseases. In this work, a Zn-0.8Li-0.4Mn alloy is designed with no biological toxicity, and optimized microstructure and properties through a hot rolling process. The resulting alloy shows a combined enhancement in both mechanical strength and resistance to corrosion. Noteworthy is the effectiveness of rolling deformation in refining alloy grains, promoting the uniform distribution of precipitates, and enhancing strength and ductility. After 90 % deformation, the Zn-0.8Li-0.4Mn alloy demonstrates excellent mechanical properties, with peak yield strength and ultimate tensile strength of 406.0 MPa and 449.1 MPa, respectively, and elongation exceeding 75 %. Corrosion studies indicate a relationship between the degradation rate increase and grain refinement, with the primary corrosion mechanism being pitting corrosion. The corrosion product Li 2 CO 3 exhibits high stability, providing a passivation effect on the alloy surface. This work establishes a theoretical foundation and practical reference for the development of new biodegradable Zn-based alloys tailored for biomedical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • A mechanical vibration assisted laser direct energy deposition process is designed to manufacture SS316L/IN718 FGM. • Cracking is eliminated by mechanical vibration through refining microstructure and restraining brittle precipitations. • The deterioration of hardness and tensile properties are significantly improved by mechanical vibration. • A crack-free and reasonable-performance SS316L/IN718 FGM is successfully achieved with the mechanical vibration assistance. In this study, a mechanical vibration assisted laser direct energy deposition was used to fabricate a functionally graded material composed of stainless steel 316L and Inconel 718. The effect of mechanical vibration on the microstructure, defects and mechanical properties of the prepared functionally graded material was studied. The results indicate that in the sample without the assistance of mechanical vibration, plenty of brittle Laves phase and NbC carbides form and induce the cracking in the specific compositional gradient range from 60 % stainless steel 316L/40 % Inconel 718 to 40 % stainless steel 316L/60 % Inconel 718. The Vickers hardness obtains a minimal value near the compositional region of 50 % stainless steel 316L/50 % Inconel 718. The tensile properties are terrible with an ultimate tensile strength of 309.7 MPa and an elongation of 7.8 %. In the sample with the assistance of mechanical vibration, the synchronous mechanical vibration could effectively restrain the cracks formation in the compositional gradient region by suppressing the brittle phases precipitation, weakening the dislocation aggregation and refining the grain size, and resultantly achieve decent tensile properties with an ultimate tensile strength of 642.6 MPa and an elongation of 22.4 % and significantly improve the deterioration of hardness in the compositional gradient region. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new austenitic stainless steel with high strength and excellent ductility was designed and manufactured by simple method. • The elongation of samples is up to 53.5–61 % under the yield and ultimate tensile strength level of 600–707 and 977–1020 MPa. • The product of strength and plasticity of this steel is the highest value comparing with other austenitic stainless steels. • There is the highest yield strength in this steel comparing with other austenitic stainless steels at the same elongation. • The excellent mechanical property of this steel is ascribed to a new multi-element collaborative strengthening mechanism. In the pursuit of simultaneously improving the yield strength and plasticity of austenitic stainless steel, a new austenitic stainless steel was fabricated by induction smelting using a pure N 2 atmosphere, hot forging, cryogenic rolling, and annealing. The material was characterized by microstructures with 3–4 μm uniform finer grains, fine precipitates, high thermal stability austenite, and extensive high-angle grain boundaries. The elongation after fracture, yield strength, and ultimate tensile strength of the samples reached 53.5 %, 707 MPa, and 1020 MPa, respectively, as well as 61 %, 600 MPa, and 977 MPa, respectively, at the same time. Moreover, a high strain hardening rate was achieved in the new stainless steel. The appropriate uniform finer grains not only played a role in grain-refined strengthening but also provided intragranular spaces and sufficient mean free available paths for dislocation accumulation and movement. Precipitates, which were coherent or semi-coherent with the matrix, provided interfaces for dislocation accumulation and obstructions for dislocation movement. Extensive high-angle grain boundaries with appropriate finer grains served as another important factor for excellent ductility due to the inhabitation and resulting deviation of crack propagation. In addition, strain-induced mechanical twinning in the current austenitic stainless steel contributed to excellent ductility and high strength. [ABSTRACT FROM AUTHOR]

[Display omitted] • Comparison between micro LPBF and conventional LPBF in the fabrication of IN718 specimens were investigated. • Increase in solidification velocity was notably more pronounced than the change in temperature gradient during μ-LPBF. • μ-LPBF demonstrated success in minimizing property anisotropy and enhancing the yield strength. • A higher volume fraction of Laves phase due to μ-LPBF indeed lead to a lower ultimate tensile strength. Compared to conventional laser powder bed fusion (c-LPBF), micro laser powder bed fusion (μ-LPBF) offers enhanced capabilities for fabricating complex components with exceptional accuracy. This is achieved through the utilization of a finer laser beam and smaller metal powder, leading to distinct differences in microstructure when compared to c-LPBF. Despite promising outcomes, a comprehensive understanding of these distinctions remains incomplete. One notable observation in the μ-LPBF samples in this study was the presence of a weaker 〈1 0 0〉 texture along the build direction. Additionally, these samples exhibited smaller grain sizes, a higher density of low-angle grain boundaries, and the presence of geometrically necessary dislocations. Significantly, μ-LPBF demonstrates the potential to produce IN718 with exceptional isotropic mechanical properties, primarily attributed to its capacity to generate refined microstructures and facilitate distinct solidification behaviors. Of particular significance was the remarkable 39.1 % increase in yield strength observed along the building direction by μ-LPBF. Furthermore, the differences in yield strength and ultimate tensile strength between various directions are notably reduced to 7 and 41 MPa, respectively, with a minimal total elongation variation of only 1.8 %. To gain deeper insights into the solidification behavior, Computational fluid dynamics were conducted in conjunction with the discrete element method. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel filaments of ultra-high molecular weight polyethylene yarn and polycaprolactone matrix were produced for 3D printing via fused filament fabrication. • An ultimate tensile strength of 500 MPa was achieved, which exceeds reported values for 3D printed composites with compliant fibers. • The printed strength and toughness decreased due to thermal degradation of fibers and depended on their dispersion within the filament. Fused filament fabrication (FFF) of composites with compliant high-strength fibers could expand opportunities for the design and fabrication of complex flexible structures, but this topic has received limited attention. This study pursued the development of filaments consisting of ultra-high molecular weight polyethylene yarn (UHMWPE) embedded in a matrix of polycaprolactone (UPE/PCL) and successful 3D printing. The physical characteristics and printability of the filament were evaluated in terms of key parameters including spooling speed, temperature, fiber distribution (consolidated vs dispersed), and fiber volume fraction (4≤ V f ≤30 %). An evaluation of the microstructure and tensile properties of the UPE/PCL was performed after processing and printing. Prior to printing, the filament exhibited an ultimate tensile strength (UTS) of 590±40 MPa with apparent fiber strength of 2.4 GPa. For the printed condition, the UTS reached 470±60 MPa and apparent fiber strength of 1.9 GPa. Fiber dispersion in the filament plays an important role on the printed properties and the potential for fiber degradation. Nevertheless, the strength of the UPE/PCL represents a new performance benchmark for compliant composites printed by FFF. This new material system can support applications where strength and toughness are key performance metrics in addition to flexibility. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tensile strength of highly-alloyed Mg-10Gd-5Y alloy is demonstrated to monotonously increase with Er content. • Solid solution strengthening and grain refinement are shown to dominate the increase of tensile yield strength upon Er content. • The significant reduced grain size with increasing Er content is correlated with both the promoted dynamic recrystallization and the retardant grain growth. The influence of Er content on mechanical properties and microstructural evolution of highly-alloyed Mg-10Gd-5Y-xEr alloys (x = 0, 2, 3.5, 5, and 6.5 wt%) are investigated. The tensile strength is found to increase monotonously with increasing Er content, while the ductility is slightly reduced due to the increased formation of block precipitates. The maximum tensile yield strength and ultimate tensile strength are achieved to be 296 MPa and 374 MPa, respectively, within the studied concertation interval. Solid solution strengthening and grain refinement are demonstrated to dominate the increase of tensile yield strength upon Er content, where the latter becomes the primary strengthening mechanism at relatively high Er contents (> 5 wt%). It is closely related to the consumption of Gd and Y in solid solution by the precipitation of Mg 24 RE 5 particles and alloying element segregation at grain boundary. The significant reduced grain size of dynamic recrystallized grains upon Er content is attributed to the promoted dynamic recrystallization via particle stimulation nucleation and the retardant grain growth emerging from the drag and pinning effect of alloying element segregation and nano-precipitates at grain boundary. [ABSTRACT FROM AUTHOR]

[Display omitted] • Corrosion induced mechanical degradation is surveyed by experiments and finite element simulation. • Stress concentration at pit leads to significant losses in strength and elongation of Zn–Cu–Li alloy. • The loss of UTS of Zn–Cu–Li alloy increases linearly with the increase of maximum pit depth. The electrochemical behavior and corrosion induced mechanical degradation of biodegradable Zn–2Cu–0.03Li alloy were in detail investigated. The results indicated that the corrosion product film presented an increasing corrosion resistance, while the localized corrosion induced by microgalvanic effect was intensified. Corrosion pits, as the typical defect, acted as the crack initiation sites and accelerated the fracture process of the Zn–2Cu–0.03Li alloy. Accordingly, the fracture mode transformed from ductile to brittle failure. Significant loss in ultimate tensile strength and elongation of the alloys occurred due to strong stress concentration at corrosion pit, threatening the mechanical reliability after implantation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Al-Mn-Cr-Zr based alloys produced via powder bed fusion-laser beam process with good process control. • Room temperature tensile properties of 550 MPa ultimate tensile strength reported (objective > 450 MPa) • High temperature tensile properties of 170 MPa yield strength reported (objective > 80 MPa) • Primary strengthening from Al 3 Zr nanoprecipitates formed upon heat treatment. Powder bed fusion-laser beam (PBF-LB), an additive manufacturing process, takes advantage of rapid cooling rates (103-106 K/s) to enable novel aluminium alloys. This study reports the mechanical properties of one such alloy system (Al-Mn-Cr-Zr based). The alloys based on this system are designed to be precipitation hardenable with high service temperatures. To elucidate the precipitation hardening, three alloy variants were studied involving different heat-treated conditions. Uniaxial tensile testing at room temperature revealed yield strengths between 250–500 MPa with elongation to fracture of 5–25 % with high repeatability. To demonstrate high-temperature resistance, two alloy variants in peak hardened condition were tested at temperatures of up to 573 K. Yield strength up to 170 MPa at 573 K was observed. These properties in combination demonstrate highly competitive Al-alloys for high-temperature applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sub-rapid solidification effectively eliminated the Mn macro-segregation of 9Mn steel. • Evolution of Mn micro-segregation and its impact on mechanical properties were studied. • Simple route to produce 9Mn steel with excellent mechanical property was developed. • Lamellar heterogeneous microstructure was induced by pre-existing austenite. • Providing a valuable solution for the green production of medium-Mn steel strip. Medium-Mn steels have garnered significant interest due to their unique combination of high strength and exceptional ductility. However, a high Mn content inevitably causes the macro-segregation of Mn, which can significantly compromise the mechanical properties. This study effectively prevented the formation of Mn macro-segregation by employing the sub-rapid solidification. It resulted in the distribution of Mn micro-segregation bands within dendritic gaps in Fe-9Mn-2Si-0.5Al-0.1C steel. Mn micro-segregation bands results in a high proportion of pre-existing austenite (γ pre) with small size and suitable stability in the as-cast strip, forming a lamellar structure with alternating distribution of lath martensite and austenite on the micrometer scale. The as-cast strip necessitates only basic simple hot rolling control without the need for any tempering treatment to achieve excellent mechanical properties comparable to conventional lengthy processes (ultimate tensile strength (UTS) of 1762 MPa, total elongation (TE) of 20 %, and product of strength and elongation (PSE) up to 35 GPa%). Utilizing this structure as a foundation, a simple austenite reverse tempering (ART) treatment can lead to additional enhancements in comprehensive mechanical characteristics with the UTS of 1529 MPa, TE of 25 % and PSE of 38 GPa%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Segregation morphology, α' lath size, γ and θ-Fe 3 C phases vary with reheat cycles. • Mechanical properties vary along built height. • Orientation of martensitic laths alters from top to bottom due to reheat cycles. • Contributions from individual strengthening mechanism varies along built height. This work investigates complex heterogeneity in microstructure and mechanical properties of a low alloy martensitic steel fabricated via laser-directed energy deposition (L-DED). A multi-scale characterization starting from macro-scale optical micrography, micro-scale X-ray diffraction and electron backscatter diffraction mapping to nano-scale transmission electron microscopy was adopted to fully comprehend the microstructural heterogeneity along the build direction. Notably, the top layers of the build demonstrated enhanced mechanical properties, exhibiting hardness of around 550 HV and an ultimate tensile strength of 2 GPa, which decreased progressively towards the base. Interestingly, resurgence in strength and hardness was observed for the layers located 10 mm above the substrate. The primary solidification cycle led to the formation of untempered martensite having high strength and hardness while subsequent reheat cycles led to the alteration of these martensites, enhancing ductility at the expense of strength. Auto-tempering and carbide (Fe-C based) precipitation due to prolonged thermal exposure contributed to the increased the strength in the lower layers. Additionally, the temperature profiles during the L-DED thermal cycles were modeled and correlated with the observed phase transformations, allowing for a detailed understanding of the structure–property relationships at different heights within the build. This study provides a fundamental insight into the microstructural heterogeneities and their implications on the strengthening mechanisms in L-DED fabricated low-alloy martensitic steel. [ABSTRACT FROM AUTHOR]

[Display omitted] • A heterostructure was fabricated via the direct warm rolling process to synergistically enhance the strength-ductility. • The heterogeneous deformation induced strengthening was the primary contributor to the increased ΔYS (782 → 1113 MPa) value. • The heterogeneous microstructure possessed more pronounced TRIP and HDI hardening effects as well as L-C locks. This work introduced a facile method for fabricating heterostructures in a medium Mn steel via a direct warm rolling process. The heavy warm rolling promoted the transformation of metastable austenite (∼12.2 vol%) into hard domain α' martensite, which formed a heterogeneous microstructure with the untransformed γ (soft domain). After 600 °C re-annealing, the hard domain α' re-reversed to α + γ, and the heterostructure disappeared. Compared to the homogeneous structure, the heterostructure exhibited the synergistic enhancement of strength-ductility (yield strength (YS): 782 → 1113 MPa; ultimate tensile strength (UTS): 1099 → 1304 MPa; total elongation (TEL): 20.8 % → 21.7 %). Quantitative analysis showed that the heterogeneous deformation induced (HDI) strengthening (∼261 MPa) was the primary contributor to the increased ΔYS (782 → 1113 MPa) value, rather than the traditional strengthening mechanisms. Transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP) effect were the main deformation mechanisms of both homogeneous/heterogeneous structures. However, compared to the homogeneous microstructure, the heterogeneous structure possessed the more pronounced TRIP and HDI hardening effects as well as L-C locks, the cooperative effect of these three factors further improved the strain hardening ability to break through the strength-ductility trade-off dilemma. [ABSTRACT FROM AUTHOR]

Abstract Cu/Al composites are perspective for applications in a wide range of industrial and commercial branches, from transportation to elecatrotechnics. This study focuses on Cu/Al clad composite wires with 5 mm in diameter featuring unique sequencing produced via the technology of rotary swaging at the processing temperatures of 20 °C and 250 °C. During the swaging process, we continuously acquired samples for investigations and used our own KOMAFU S600 system for dynamic detection of swaging forces. The composite wires subjected to electrical resistivity measurement were further analysed via electron microscopy, neutron diffraction, and mechanical testing. The results showed that both the total imposed strain (swaging degree) and swaging temperature influenced the investigated parameters non-negligibly. The samples subjected to high reduction ratios (swaging degree > 3) at the temperature of 250 °C exhibited formation of intermetallics at the interfaces, which deteriorated the electric conductivity. However, the conductivity was also affected by structural phenomena, such as work hardening, texture development, dislocations density, and recrystallization. All the final 5 mm samples exhibited sufficient bonding of both the components and recrystallized ultra-fine grained structures providing them with the ultimate tensile strength of >200 MPa. Graphical abstract Unlabelled Image Highlights • Clad composite wires with 5 mm diameter were produced via rotary swaging. • Composite structures featured ultra-fine grains. • Room temperature swaging induced neglectable intermetallics development. • Work hardening increased ultimate tensile strength to approx. 250 MPa. • Structure restoration and refinement increased electric conductivity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Spherical Titanium/Niobium/Tantalum powders were successfully produced in a wide range of chemical composition by electrode induction melting gas atomization. • Fully dense structures are reported after additive manufacturing using laser powder bed fusion. • Phase composition and microstructures of additively manufactured parts can be directly tailored by varying the Titanium:Niobium:Tantalum stoichiometry in the alloys. • Mechanical properties, i.e., ultimate tensile strength and elongation at fracture, strongly depend on microstructure and composition. The synthesis of spherical titanium/niobium/tantalum (TNT) alloy powders, namely Ti-20Nb-6Ta, Ti-27Nb-6Ta, Ti-35Nb-6Ta, and Ti-22Nb-19Ta (in wt-%) by electrode induction melting gas atomization is reported. The powder materials are characterized in detail using X-ray diffraction and scanning electron microscopy. Their processability via laser beam powder bed fusion (PBF-LB/M) is proven, and microstructure as well as mechanical properties of the additively manufactured specimens are assessed. All powders feature a dendrite-type microstructure with Nb/Ta-rich dendritic and Ti-rich inter-dendritic phases. Crystal structures of the powders are strongly composition-dependent. Nb- and Ta-rich Ti-35Nb-6Ta and Ti-22Nb-19Ta feature a body-centered cubic lattice, whereas Ti-rich Ti-20Nb-6Ta and Ti-27Nb-6Ta powders are characterized by multi-phase microstructures, consisting of non-equilibrium martensitic phases. Processing by PBF-LB/M causes significant changes in their microstructures: the dendrite-type morphologies vanish, and the formation of microstructures with a homogeneous element distribution can be observed in all additively manufactured parts. Ultimate tensile strength (UTS) as well as elongation at fracture are assessed by tensile testing. UTS values are found to be in a range from 651 MPa (Ti-35Nb-6Ta) to 802 MPa (Ti-20Nb-6Ta); strain-to-failure is between 21.3 % (Ti-35Nb-6Ta) and 31.7 % (Ti-22Nb-19Ta). Ductile fracture behavior is seen for all TNT alloys investigated. [ABSTRACT FROM AUTHOR]

[Display omitted] • AA7075/TiB 2 composites with up to 24 vol% TiB 2 are produced with friction consolidation. TiB 2 fragmented into submicron- and micron-sized particles by intense deformation. • 24 vol% composite has a very high strength of 672 MPa and a wear rate of 5.7x10−5 mm3/Nm, both of which surpasses the other AMC examples in the literature. • Microstructure-based FE simulations predict the theoretical strength of ∼730 MPa and the failure mechanisms in the composites. Strain localization in between the particles limits the ductility. The friction consolidation method successfully reinforced aluminum 7075 alloy (AA7075) with high-volume fractions (12 and 24 vol%) of titanium diboride (TiB 2) by high pressure and severe plastic deformation at elevated temperatures. The consolidated AMCs have a uniform dispersion of submicron- and micron-sized TiB 2 particles in the AA7075 matrix, with significant refinement of the matrix grain size and the particles. The addition of TiB 2 significantly increases hardness by up to 50 %, Young's modulus by up to 62 %, and ultimate tensile strength by up to 28 % to 672 MPa, while reducing ductility by 80 %. Wear resistance of 7075/24 vol% TiB 2 improves seven-fold compared to baseline, making it comparable to that of carburized steels. Microstructure-based finite element modeling provided a theoretical strength limit of ∼730 MPa for the composites and indicated that high triaxiality in conjunction with severe equivalent plastic strain in a narrow area between the TiB 2 particles led to early fracture initiations, limiting the ductility. [ABSTRACT FROM AUTHOR]

[Display omitted] • The introduction and retention of austenite during warm rolling is beneficial to the improvement of mechanical properties. • Warm rolling in dual-phase region and tempering induces the formation of multi-heterogeneous austenite morphologies. • The formation of superlattice structures is attributed to the construction of stacking fault networks. Facing the current lack of clarity in temperature selection mechanisms for warm rolling in medium Mn steel, three warm rolling methods were conducted in 3Mn steel according to the rolling temperatures in the dual-phases region or ferrite region. Subsequently, the effect of heat treatment on the austenite morphologies and tensile properties of warm-rolling samples was studied. Rolling in dual-phase regions (750 °C) led to heterogeneous austenite morphology composed of equiaxed and lamellar grains while rolling in the ferrite region (600 °C) resulted in significant cementite precipitation and the absence of retained austenite. Warm rolling promoted the formation of dislocation cells in the lath-like grains, and they did not evolve into grain boundaries completely because low deformation temperature didn't trigger the complete dynamic recrystallization. Tempering after rolling provided a significant enhancement in plasticity through the enrichment of C and Mn in austenite and the formation of multiple heterogeneous austenite morphologies with equiaxed, coarse lath-like and fine lamellar grains. In addition, superlattice structures in the matrix are formed through the formation of stacking fault networks and the spinodal decomposition. Ultimately, the exceptional properties were achieved in 3Mn steel, with an ultimate tensile strength of 1409 MPa and a total elongation of 27.3 %. [ABSTRACT FROM AUTHOR]

[Display omitted] • A route to microstructure design was unraveling through combination of cryogenic ECAP followed by ageing in a CuCrZr alloy. • ECAP at room and cryogenic temperatures significantly improved hardness, yield strength and ultimate tensile strength. • The best combination of strength and ductility achieved so far for CuCrZr alloys. • Cr-rich precipitates played a dual role by boosting mechanical strength and hindering grain boundary motion. • Ageing after CT-ECAP offered an effective thermomechanical route for thermal stabilization. This investigation aimed to design a thermally stable microstructure of an ITER-grade Cu-0.7Cr-0.07Zr alloy. The chosen approach involved employing a novel Equal Channel Angular Pressing (ECAP) at cryogenic temperatures (CT), in which the temperature was strictly controlled, followed by subsequent ageing. Post-ECAP ageing at 400 °C for 15 min resulted in a substantial enhancement in yield strength in CT-processed specimens, with a remarkable increase of 22% in comparison to their pre-aged counterparts. Additionally, ageing under these conditions yielded a more stable microstructure at elevated temperatures, with average grain size variation below to 1 μm. The observed stability was attributed to the formation of fine Cr-rich precipitates during ageing that hinder grain boundary motion, thereby preventing grain growth and potential softening of the CuCrZr alloy. These findings elucidate a promising thermomechanical processing avenue for strengthening microstructures processed by cryogenic severe plastic deformation and/or exposure to elevated temperatures. Finally, the adopted processing route in this study not only facilitated but distinctly culminated in attaining the paramount strength/ductility relationship for CuCrZr alloys with a stable microstructure at medium-to-high temperature range. [ABSTRACT FROM AUTHOR]

[Display omitted] • The microstructure and mechanical anisotropy of additively manufactured CoCrNi medium-entropy alloys were studied after HIP and UIT. • HIP induces the formation of large number of Cr 2 O 3 particles, and transformation of LAGBs into HAGBs. • UIT contributed to the increase in the number of LAGBs and induced the transformation of columnar grains to equiaxed grains, thus decreasing the anisotropy of AM CoCrNi MEAs. The anisotropy properties of samples in different direction is found in additively manufactured (AM) CoCrNi medium-entropy alloys (MEAs). In this study, the laser direct energy deposition AM CoCrNi MEAs have been subjected to two alternative processing methods: hot isostatic pressing (HIP) and ultrasonic impact treatment (UIT). The effect of HIP and UIT on the microstructure, grain orientation, grain boundary distribution, phase distribution and mechanical properties of AM CoCrNi MEAs were systematically studied. The results show that HIP decreased the partial mechanical anisotropy of AM CoCrNi MEAs, and YS was significantly reduced. The main reason is that the HIP induces the formation of large number of Cr 2 O 3 particles, and transformation of low-angle grain boundaries (LAGBs) into high-angle grain boundaries (HAGBs). Surprisingly, both the yield strength (YS) and ultimate tensile strength (UTS) of the AM CoCrNi MEAs were increased when the UIT was added after every laser deposition of one layer (UIT-1). This is due to the combined effect of quasi-static loading and ultrasonic oscillations of UIT, which results in the dislocation multiplication and the formation of a large number of substructures. In addition, the above strengthening phenomena also lead to decrease partial mechanical anisotropy of AM CoCrNi MEAs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Molecular dynamics simulations are conducted to investigate the Young's modulus and ultimate tensile strength of graphene reinforced aluminium nanocomposites. • Machine learning (ML) techniques are used to predict the mechanical properties based on MD datasets. • Halpin-Tsai model is modified in explicit form based on MD and ML results. • Modified Halpin-Tsai model has significantly improved accuracy for the prediction of Young's modulus. Predicting mechanical properties of graphene-reinforced metal matrix nanocomposites (GRMMNCs) usually requires atomistic simulations that are computationally expensive without scalability or micromechanics-based models (such as widely used Halpin-Tsai model) that may lead to considerable errors in many cases. This paper first combines molecular dynamic (MD) simulation and machine learning (ML) techniques to predict the mechanical properties of graphene reinforced aluminium (Gr/Al) nanocomposites and use them to modify Halpin-Tsai model. Extensive MD results for Young's modulus and ultimate tensile strength of Gr/Al nanocomposites are obtained, with the intricate effects of graphene's volume fraction, alignment angle, chirality and environment temperature being taken into account. After training and optimization based on MD data, ML models are developed with the capability in estimating Young's modulus and ultimate tensile strength. The micromechanics based Halpin-Tsai model is then modified by using the Young's modulus predicted by both MD and ML models such that the Young's modulus can be readily determined with significantly improved accuracy from an explicit relationship that is very easy to use in the analysis and engineering design of Gr/Al nanocomposite structures. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mold-filling capacity and mechanical properties of Al-Cu-Mn alloy were improved by adding appropriate Ni element. • After T6 treatment, the Ni-rich eutectic phase spheroidized into discrete particles and distributed along grain boundaries. • Proper addition of Ni will lead to Ni atoms segregated into the interface between the Mn-rich phase and α-Al matrix, which reduces the interfacial energy of Mn-rich phase and prevents it from growing. • The Al-5Cu-1Mn-1Ni alloy have the optimum mechanical properties with ultimate tensile strength, yield strength and elongation at fracture reaching 505MPa, 348MPa and 16.5%, respectively. In this study, the effects of Ni content on the microstructure and mechanical properties of Al-5.0Cu-1Mn-based alloys were investigated. The results demonstrate that Ni alloying refines the grain size and enhances castability. At low Ni content, some of Ni atoms participate in forming Al 7 Cu 4 Ni at the grain boundaries. The rest Ni segregates to the interface between α-Al and AlCu 3 Mn 2 phase, which inhibits AlCu 3 Mn 2 growth. The amount of Ni-rich phase at grain boundaries increases significantly as Ni concentration increases at the expense of the decline precipitates. After T6 treatment, the lamellar Ni-rich phase spheroidized into discrete particles that were uniformly distributed along the grain boundaries. Ni-rich phase of particles can effectively pin grain boundaries and prevent grain rotation. The optimum mechanical property is achieved with 1% Ni addition, predominantly due to the synergistic strengthening of eutectic strengthening and precipitation strengthening. The ultimate tensile strength, yield strength and elongation reach 505 MPa, 348 MPa and 16.5% respectively, which far exceed the current commercial cast aluminium alloys. With increasing Ni concentration, the fracture mode of the alloy changes from ductile fracture to brittle-ductile mixed fracture, because the high amount of Ni-rich phase intermetallic compounds increase the sites for localized brittle fractures. [ABSTRACT FROM AUTHOR]

This paper investigates the mechanical properties of hyper deformed wires of Ti-26 at.%Nb (Ti-26Nb) alloy that can be equally expressed as Ti-40.5 wt.%Nb. These wires obtained by hot drawing process have a diameter of 85 μm and 285 μm, respectively. The effect of a short heat treatment at 748 K for 600 s was also investigated. The influence of the heat treatment and the diameter of the wires evaluated by mechanical tests, such as nano indentation, quasi-static tensile, and fatigue tests, and microstructure investigations. The quasi-static tensile tests show that the mechanical properties, like elasticity modulus and ultimate tensile strength, are improved with the decrease of the diameter. An increase of 55% and 26% in strength is obtained for the non-treated state and the heat treated state, respectively. The improvements in the mechanical properties for the 285 μm diameter wire are due to the refinement of grains to submicron scale between 100 and 200 nm. The short heat treatment induces an increase of the Young's modulus and a decrease of the ultimate tensile strength by the emergence of a dual phase ( α and β ) microstructure. For fatigue tests, the increase of frequency from 4Hz to 30Hz leads to an increase of 45% of the fatigue life time. [ABSTRACT FROM AUTHOR]

[Display omitted] • The influence of aging on the microstructural and mechanical properties of LPBF-processed Ti-42Nb alloy was investigated. • The formation of the metastable orthorhombic α i s o ' ' phase was revealed. • A clear influence of the as-built microstructure on the number, size, and morphology of the precipitates was demonstrated. • A preferential hardening of the grain boundary regions was shown. • An exceptional improvement (∼50 %) in the tensile strength was achieved compared to the as-built state. This study provides a comprehensive analysis of a Ti‑42Nb alloy produced via laser powder bed fusion (LPBF) with varying post-heat treatment durations within the α + β phase range at 723 K. Synchrotron XRD analysis revealed the formation of the metastable orthorhombic α iso ' ' phase during heat treatment, acting as an intermediate to the stable α phase. With prolonged heat treatment, the α iso ' ' phase fraction increased, reaching approximately 25 % after 108.0 ks. SEM analysis identified β grain boundaries as primary sites for early α iso '' precipitation, while intragranular α i s o ' ' precipitation was delayed. Up to 28.8 ks, volume fraction and size of intragranular precipitates exhibited notable variations due to minor Nb content fluctuations from LPBF processing, resulting in an increased spread of hardness and Young's modulus on the micro scale. Tensile tests revealed significant strength enhancement through post-heat treatment for 108 ks compared to the as-built state, achieving a yield strength of around 1060 MPa (50 % increase) and ultimate tensile strength of 1125 MPa (55 % increase). Extended growth of the α i s o ' ' phase led to an increased Young's modulus, reaching 87 GPa after 108.0 ks. These findings provide valuable insights for developing post-heat treatment strategies for LPBF-produced Ti‑42Nb implants, including both bulk materials and lattice structures. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pure copper electrodes were produced by the laser powder bed fusion technique. • The microstructure of the part was examined in different areas. • The effect of the thermal history on the porosity percentage was studied through the height. • The electrical and thermal properties of the additively manufactured parts were compared to the original cast part. • Additively manufactured pure copper electrode corrosion in two different environments was evaluated. This study explores the fabrication and characterization of a pure copper electrode for an EDM equipment using laser powder bed fusion (LPBF) and comparing its performance with an original cast sample. The microstructural, mechanical, electrical, thermal, and corrosion characteristics of the samples were analyzed. The microstructure of the additively manufactured (AM) sample exhibited superior mechanical properties, with an 18 % increase in ultimate tensile strength and more than two times greater elongation in comparison with those of the cast sample. Moreover, the electrical and thermal conductivity coefficients of the AM sample were found to be consistent with industry standards as 5.52 × 107 S/m and 361 W/mK, respectively. Additionally, the potentiodynamic polarization corrosion test results of the AM sample further exhibited superior corrosion resistance in terms of the corrosion potential particularly in a 3.5 % NaCl environment. Advanced electron microscopy techniques were used to investigate the differences in the properties of the AM and cast samples and further shed light on the superior properties of the LPBF counterpart. Despite challenges in manufacturing pure copper components through LPBF, this study demonstrates the feasibility of producing a functional part that competes effectively with cast counterparts and excels in certain aspects. [ABSTRACT FROM AUTHOR]

[Display omitted] • The prepared Mg-Li matrix composite achieves a combination of high Young's modulus (60 GPa) and ductility. • Precipitations on the TiB 2 surface are observed and identified for the first time in Mg-Li matrix composites. • The precipitations on the TiB 2 ′s surface improves ductility by absorbing stress and reducing dislocations. The development and application of lightweight materials boasting an elevated elastic modulus have emerged as a focal point in the realm of materials research. A novel Mg-8Li-3Al-2Zn-0.5Y (wt.%, LAZ832) matrix composite reinforced with ex situ micron-sized TiB 2 particles was introduced in this work. The uniformly distributed TiB 2 particles were achieved through ball milling pretreatment and subsequent hot extrusion. A comprehensive analysis of the composite's microstructure and mechanical properties was conducted. Mg-Li-Al-Zn precipitation regions formed at the TiB 2 interface was identified firstly. This softening region significantly enhanced the ductility of the composite by reducing the dislocation density and stress concentration around the TiB 2 particles. The ductility and the elastic modulus of the as-extruded composite increased significantly with ideal ultimate tensile strength (UTS = 270 MPa). This work highlights an ultra-light Mg-Li matrix composite attaining high modulus (60 GPa) and notable elongation to fracture (19.1 %), demonstrating significant potential for future applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel Al-Ni-Ti-Zr-Mn alloy processed by L-PBFAM with extraordinary 502 MPa strength. • Bimodal particle strengthening combined with solid solution strengthening by entrapped Mn imparts strength. • Rejected Al 31 Mn 6 Ni 12 nano-quasi-crystalline particles within Al 3 Ni dendrites contribute to bimodal strengthening. • Spatial variations in strengthening are mapped to hierarchical heat distribution associated with L-PBFAM. The unique thermokinetics of laser-powder bed fusion additive manufacturing (L-PBFAM) has been exploited for development of a novel high-strength Al-Ni-Ti-Zr-Mn alloy. The addition of 0.5 wt% Mn leads to extraordinary improvement in ultimate tensile strength (502 MPa) and work hardening due to the activation of two Mn-induced strengthening mechanisms. First, by a bimodal particle strengthening effect due to Al 31 Mn 6 Ni 12 nano-quasi-crystal particles rejected in inter-dendritic spaces and fibrous Al 3 Ni eutectic dendritic channels, which predominately contributes to the strength improvement, and second by solid solution strengthening from remaining Mn entrapped in Al. These mechanisms supplement the particle strengthening effect imparted by coherent and incoherent Al 3 (Ti,Zr) co-precipitates present at melt pool boundaries, dislocation strengthening due to solidification induced strain, and Hall-Petch and backstress strengthening effect due to heterogenous grain size distribution occurring at various length scales. The solidification dynamics and hierarchical heat distribution that are associated with L-PBFAM resulted in complex spatial variations in these strengthening phenomena and were investigated via a high-throughput multiscale structure–property correlation that involved thermokinetic simulation, X-ray diffraction, high-resolution nanoindentation mapping, and site-specific transmission electron microscopy of the alloy. [ABSTRACT FROM AUTHOR]

[Display omitted] • A low-cost composite (LMC-CS) was designed, which simultaneously exhibited high strength and low HE susceptibility. • Austenitic layer blocks and absorbs the majority of hydrogen, maintaining ductile failure in LMC-CS after fracture. • Semi-coherent composite interface is generated inside DRX grains by the limited element diffusion. • The semi-coherent composite interface deeply trapped hydrogen, thereby hindering hydrogen-induced crack initiation. High-strength metallic materials with low hydrogen embrittlement (HE) susceptibility have always been regarded as ideal commercial materials in the hydrogen energy field. This work proposed a low-cost laminated metal composite (LMC-CS) consisting of austenitic stainless steel (ASS) layer and martensitic steel (MART) layer, which simultaneously achieved high mechanical strength with excellent HE resistance. The ASS layers provide additional strain-hardening capability and the MART layer contributes high strength to LMC-CS after H-charging. Additionally, the composite interface displays semi-coherent characteristics, and the atomic arrangement on both sides follows the Kurdjumov-Sachs orientation relationship with (1 1 ¯ 0) α-Fe // ( 1 ¯ 1 1 ¯ ) γ-Fe and [1 1 1] α-Fe // [1 1 0] γ-Fe and the Nishiyama–Wassermann orientation relationship with ( 1 ¯ 1 ¯ 0) α-Fe // ( 1 ¯ 11) γ-Fe and [0 0 1] α-Fe // [ 01 1 ¯ ] γ-Fe., which coordinates deformation between layers and hinders hydrogen-induced cracks initiation at the interface. The as-designed LMC-CS achieves an ultimate tensile strength of 1102 MPa and an elongation loss of 14.8% after long-time hydrogen charging with sides sealed, outperforming a wide range of metallic materials. This work provides a fresh perspective on developing commercial materials with high strength and superior HE resistance for application in severe hydrogen environments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mg-Ag microalloying ameliorates the detrimental agglomeration of TiB 2 particles by segregating at the TiB 2 /α-Al interface. • Mg-Ag co-clusters act as favorable nucleation sites for the Ω-Al 2 Cu and σ-Al 5 Cu 6 Mg 2 phases assisted by multistage heat treatment. • The acquired 5TiB 2 /Al-4.5Cu-0.5 Mg-0.6Ag composite yields an ultimate tensile strength of 496.3 ± 15.0 MPa and uniform elongation of 12.8 ± 1.4 %. The strength-ductility trade-off severely limits the extensive application of particle-reinforced aluminum matrix composites mainly owing to the critical issues of local particle agglomeration and poor interfacial characteristics. The present work concentrates on these intractable puzzles and proposes Mg-Ag microalloying TiB 2 /Al-4.5Cu composites fabricated by an optimized salt-metal reaction method and multistage heat treatment. The resulting microstructure evidence that this new tactic synergistically ameliorates the detrimental agglomeration of TiB 2 particles by Mg and Ag doped at the TiB 2 /α-Al interface， meanwhile promoting the formation of nanosized Ω-Al 2 Cu and σ-Al 5 Cu 6 Mg 2 phases. The mechanical property experimental results indicate that the Mg-Ag microalloyed TiB 2 /Al-4.5Cu composites exhibit an accredited combination of the tensile strength (ultimate tensile strength is 496.3 ± 15.0 MPa) and ductility (uniform elongation is 12.8 ± 1.4 %). We emphasize the reciprocal effect between TiB 2 particles and the precipitated phase associated with unrelaxed misfit strains. Close attention is also paid to the interface binding characteristics and semi-coherent interphase boundary to evaluate their contribution to the ductility. The microalloying strategy can potentially be applied to many other metal matrix composites and boost analogous approaches for designing ultrahigh yet ductile materials for technological applications. [ABSTRACT FROM AUTHOR]

To meet the need for high strength tubes for various industrial applications, a new method, known as hydrostatic extrusion integrated with circular equal channel angular pressing (HECCAP), was proposed for the fabrication of AZ80 magnesium alloy tubes. Small diameter billets could be extruded into tubes of larger diameters using this method. The effects of the extrusion ratio (ER) and the conical mandrel angle (CMA) on the microstructure and tensile properties of the AZ80 magnesium alloy tube were investigated. The HECCAP-treated alloys exhibited a partial dynamically recrystallized microstructure. More shear zones formed inside of these grains, and a higher recrystallization grain volume fraction were presented in the alloy after HECCAP treatment with a larger ER or CMA values. The tensile yield strength, ultimate tensile strength, and elongation percent increased as ER and CMA also increase. The highest ultimate tensile strength, tensile yield strength and elongation were 335 MPa, 308 MPa, and 7.2%, respectively, at an ER of 2.77 and CMA of 120°. A formula was proposed to calculate the total generated plastic strain after HECCAP, which increased with increasing ER and CMA. [ABSTRACT FROM AUTHOR]

Optimum laser irradiation conditions to achieve dense A356.0 (AlSi7Mg0.3) specimens fabricated by selective laser melting (SLM) were studied. The SLM specimens with relative density of 99.8% were obtained. The microstructures and mechanical properties of the dense SLM specimens fabricated under the optimum laser irradiation conditions were also investigated. The dense SLM specimens had an ultimate tensile strength, yield strength, and breaking elongation of 400 MPa, 200 MPa, and 12-17%, respectively. All of these values considerably exceeded those in cast-melting materials. The superior mechanical properties of the SLM specimens could be attributed to fine dendritic cell microstructures and relative density of almost 100%. An investigation of the heat treatment effects on the microstructures and mechanical properties revealed a clear difference in annealing behaviors between the SLM specimens and the cast-melting materials. After annealing (T5), the breaking elongation of the SLM specimen increased from 15% in the as-fabricated specimen to 30% in the specimen annealed at 350 °C, while the ultimate tensile strength and yield strength decreased from 400 MPa and 250 MPa to 200 MPa and 125 MPa, respectively. This confirmed that the mechanical properties of the SLM specimens could be controlled in accordance with required functions for design. [ABSTRACT FROM AUTHOR]

Conventional dual phase (DP) steel (0.08C-0.81Si-1.47Mn-0.03Al wt.%) was manufactured using simulated strip casting schedule in laboratory. The average grain size of prior austenite was 117 ± 44 µm. The continuous cooling transformation diagram was obtained. The microstructures having polygonal ferrite in the range of 40-90%, martensite with small amount of bainite and Widmanstätten ferrite were observed, leading to an ultimate tensile strength in the range of 461-623 MPa and a corresponding total elongation in the range of 0.31-0.10. All samples exhibited three strain hardening stages. The predominant fracture mode of the studied steel was ductile, with the presence of some isolated cleavage facets, the number of which increased with an increase in martensite fraction. Compared to those of hot rolled DP steels, yield strength and ultimate tensile strength are lower due to large ferrite grain size, coarse martensite area and Widmanstätten ferrite. [ABSTRACT FROM AUTHOR]

For the first stage, a metastable β titanium alloy, Ti-3.5Al-5Mo-4V-2Cr-2Sn-2Zr-1Fe reinforced with trace amounts of TiB whiskers and TiC particles was fabricated by vacuum arc melting process and hot forging followed by heat treatment at 780 °C/740 °C, then by aging at 500 °C, 550 °C, 570 °C and 600 °C. For the second stage, the unreinforced titanium alloy was also fabricated by the same process. The microstructural characteristics were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Traces of TiB whiskers and TiC particles (2.2 vol.%) with a volume ratio of 2:3 synthesized in situ exerted a hybrid reinforcing effect on the β titanium alloy. The reinforcements were uniformly distributed in the matrix and the elastic modulus was improved about 25 GPa. Ultimate tensile strength and yield strength achieves about 1625 MPa and 1500MPa respectively, with ductility at 7% when the aging temperature is 500 °C. The ductility of (TiB + TiC)/(Ti-3.5Al-5Mo-4 V-2Cr-2Sn-2Zr-1Fe) matrix composite could be enhanced by increasing the aging temperatures. After 780 °C followed by aging at 570 °C, excellent strength and plasticity properties were obtained (ultimate tensile strength of matrix alloy is 1350 MPa with elongation of 18% and ultimate tensile strength of composite is 1500 MPa with elongation of 13%). [ABSTRACT FROM AUTHOR]

High strength low alloy steels are characterised by predominantly ferritic microstructures, strengthened by grain boundary and precipitation strengthening. Both of these strengthening mechanisms traditionally arise from the niobium addition. Increasing the niobium addition would theoretically increase strength. However, increasing niobium content above ~ 0.04 wt.% is not recommended in industrial practice due to narrowing of the annealing process window. Two novel grades exhibiting different additions of titanium and vanadium in place of the traditional niobium addition were investigated. Sensitivity to annealing linespeed and soak temperature was investigated to conclude whether a practically achievable process window exists and moreover, to conclude whether proof strength in excess of 420 MPa could be achieved while satisfying the maximum ultimate tensile strength and minimum total elongation specifications of CEN Grade HC420LA under European Standard EN 10268:2006. One of the two novel grades, exhibiting higher manganese and vanadium contents, met the minimum proof strength target, while almost satisfying the maximum ultimate tensile strength and minimum total elongation specifications. However, the annealed microstructure was found to be partially recrystallised, which is not recommended in industrial practice. Moreover, sensitivity to annealing linespeed and soak temperature was considered too great to obtain a practically achievable process window. [ABSTRACT FROM AUTHOR]

Aluminum has been used as an alternative to copper for the production of electrical grade conductors. However, good electrical conductivity with excellent mechanical properties is hard to realize. Grain refinement can improve plastic deformation and mechanical properties. Boron treatment is advantageous to the improvement of electrical conductivity. So it is promising to achieve good mechanical properties and electrical conductivity by the interaction of grain refinement and boron treatment. In our work, the effect of grain refinement and boron treatment on electrical conductivity and mechanical properties of AA1070 aluminum was studied. The ideal grain refiner is Al-5Ti-0.8B-0.2C master alloy and with 0.2% addition, the electrical conductivity keeps at 60.7% IACS. Besides, the effect of different boron additions on electrical conductivity of AA1070 aluminum was studied. With 1%Al-6B addition, its electrical conductivity can reach 64% IACS, improved by 5.3%. With 0.2%Al-6B and 0.5%Al-5Ti-0.8B-0.2C additions, the electrical conductivity can reach 63.2% IACS, ultimate tensile strength at room temperature (UTS25 °C) is 85 MPa, and elongation (Ɛ) is 58%. Compared with AA1070 aluminum without addition, the ultimate tensile strength and elongation have been improved by 26.9% and 9.4% separately. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new phase MgSn (Gd, Dy) is formed and its effect on MgSnGd particles are clarified. • The modified MgSnGd phase promote dynamic recrystallization process. • Achieving the excellent comprehensive mechanical properties of ZMT813-1.2Gd-0.2Dy alloy. In the current work, we successfully prepared Mg-8Zn-1Mn-3Sn-1.2Gd-0.2Dy alloy with an excellent combination of ultimate tensile strength and ductility. The mechanism of the Dy-modified MgSnGd phase and its effect on the microstructure and mechanical properties of as-cast and as-extruded alloy were systematically investigated. Experimental results reveal that a new phase MgSn (Gd, Dy) is formed with Dy addition to Mg-8Zn-1Mn-3Sn-1.2Gd alloy, MgSn (Gd, Dy) phase can act as an effective heterogeneous nucleation site of MgSnGd phase. Meanwhile, the addition of Dy consumes Sn and Gd atoms, reducing the enrichment of solute atoms and inhibiting the MgSnGd phase's growth. The Dy addition can effectively promote the dynamic recrystallization process due to the combined effects of the refined grain structure of as-cast alloy and the particle-stimulated nucleation effect caused by dispersed MgSnGd phase. The alloy exhibits an excellent combination of high strength and ductility with the ultimate tensile strength of 384 MPa and an elongation of 14.5%. The fine-grained structure, the uniformly distributed MgSnGd particle, and MgSn (Gd, Dy) nanoparticles are mainly responsible for the ultra-high ultimate tensile strength. The high ductility is due to the fine-grained structure, appropriate decrease of dislocation density, and dynamic recrystallization. [ABSTRACT FROM AUTHOR]

Two-stage creep-aging behavior of an Al–Cu–Mg alloy are studied by uniaxial tensile creep tests over wide ranges of temperature and external stress. Effects of creep-aging temperature and external stress on mechanical properties are discussed. It is found that the mechanical properties of the studied Al–Cu–Mg alloy are strongly sensitive to the creep-aging parameters. The two-stage creep-aging processing can change the characteristics of aging precipitates and dislocations, which greatly affects the mechanical properties of the studied Al–Cu–Mg alloy. With the increase of the second stage creep-aging temperature, the yield strength increases, while the ultimate tensile strength and elongation decrease. Meanwhile, the yield strength decreases with the increase of external stress. However, the ultimate tensile strength and elongation first increase and then decrease when the external stress is continuously increased within the tested conditions. Additionally, the mechanical properties of the two-stage creep-aged alloy are better than those of one-stage creep-aged and stress-free aged alloys. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of the rheoformed parts of 7075 aluminum matrix composite were investigated. The results show that more liquid phase and spheroidal solid grains were found in the microstructures in the top and medium regions of the side wall of the rheoformed parts due to dependence of the deformation on liquid flow and flow of liquid incorporating solid grains. Yield strength and ultimate tensile strength of the rheoformed composite parts are enhanced as compared with the as-extruded and the rheoformed parts of 7075 matrix alloy. The yield strength, ultimate tensile strength and elongation of the rheoformed composite parts with T6 reach 399 MPa, 492 MPa and 9.6%, respectively. When stirring time increases from 5 min to 20 min, the mechanical properties increased due to fine-grained strengthening and a further increase more than 20 min led to a slight change. Pressure led to a significant increase of the mechanical properties due to some reduction of defects and dislocations strengthening. An increase of SiC volume fraction from 0.5% to 1% led to an improvement of yield strength and ultimate tensile strength and a further increase led to a decrease. [ABSTRACT FROM AUTHOR]

The effects of superheat temperature, content of modifier (P) and T6 heat treatment on the microstructure and mechanical properties of the Al–50Si alloy have been investigated systematically by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The results indicate that the primary Si exhibits a plate-like morphology, with average size decreasing with increasing of the superheat temperature for the unmodified alloy. The morphology of primary Si changes to small blocky shape at an optimal P content of 0.5 wt.%, and the nucleation temperature increases for the alloy with 1.3 wt.% P because of the ease of formation of the AlP phase. The nucleation temperature is lower for 0.5 wt.% P due to lack of P atoms at relatively higher temperature. The ultimate tensile strength was enhanced by the addition of P followed by the T6 heat treatment, and the maximum ultimate tensile strength (∼160 MPa) was observed for the sample containing 0.5 wt.% P. [ABSTRACT FROM AUTHOR]

Heat treatment with different parameters were performed on the hot-hydrostatically extruded and swaged 3.5 vol.% TiBw/Ti6Al4V composites tubes. The results indicate that the primary α phase volume fraction decreases and transformed β phase correspondingly increases with increasing solution temperatures. The α + β phases will grow into coarse α phases when the aging temperature is higher than 600 °C. The hardness and ultimate tensile strength of the as-swaged TiBw/Ti6Al4V composite tubes increase with increasing quenching temperatures from 900 to 990 °C, while they decrease with increasing aging temperatures from 550 to 650 °C. A superior combination of ultimate tensile strength (1388 MPa) and elongation (6.1%) has been obtained by quenching at 960 °C and aging at 550 °C for 6 h. High temperature tensile tests at 400–600 °C show that the dominant failure modes at high temperatures also differ from those at room temperature. [ABSTRACT FROM AUTHOR]

This paper presents experimental results and analysis of the behaviour of heat-resistant austenitic steel (X15CrNiSi25-20) subjected to uniaxial stress at room and high temperatures. The results include stress–strain diagrams as well as creep curves showing the behaviour of material responses to different temperatures. The experimental results of Charpy impact energies provide the ability to asses fracture toughness. On the basis of stress–strain diagrams it is possible to determine ultimate tensile strength, yield strength, modulus of elasticity and total elongation. Also, from creep curves it is possible to analyse material ’ s resistance to creep at considered temperatures. Descriptive error bars relating to mechanical properties are also presented. Finally, the dependence of mechanical properties on strain rate is shown. Experimental results show that this steel is characterised by both high ultimate tensile strength (688 MPa/20 °C; 142 MPa/800 °C) and yield strength (498 MPa/20 °C; 132 MPa/800 °C) throughout the range of the investigated temperature field. Its creep resistance at temperatures of 500 °C and 600 °C may be treated as good if stress levels do not exceed: 280 MPa/500 °C and 130 MPa/600 °C. [ABSTRACT FROM AUTHOR]

Samples made of a super high strength aluminum alloy with high Zn content were friction stir welded with rotation rates of 350–950 rpm and welding speeds of 50–150 mm/min. The effect of welding parameters on the microstructure and mechanical properties was investigated. It was observed that the grain size of the nugget zones decreased with the increasing welding speed or the decreasing tool rotation rate. Most of the strengthening precipitates in the nugget zone were dissolved back and the intragranular and grain boundary precipitates in the heat affected zone coarsened significantly. The greatest ultimate tensile strength of 484 MPa and largest elongation of 9.4 were obtained at 350 rpm−100 mm/min and 350 rpm−50 mm/min, respectively. The ultimate tensile strength and elongation deteriorated drastically when rotation rate increased from 350 to 950 rpm at a constant welding speed of 100 mm/min. [ABSTRACT FROM AUTHOR]

[Display omitted] • The brittle sigma and chi phases were inhibited while the Laves phase was promoted by Al modification. • The pinning of Laves phase and the solute drag of Al hindered the movement of grain boundaries. • Al modification reduces the risk of material embrittlement and promotes improved mechanical properties. • Al-modified ultra-super ferritic stainless steels have been successfully developed and require further research. An isothermal ageing experiment was carried out to investigate the influence of Al modification on the brittle phase precipitation behaviour, grain coarsening and mechanical properties of newly designed ultra-super ferritic stainless steel. Experimental results demonstrated that the modification of Al significantly inhibited the formation rate of the sigma phase, retarded the induction period of the chi phase, and promoted the growth process of the Laves phase. Meanwhile, the calculated grain growth kinetics of the surface layer and core layer were compared with the measured values. It was found that the Al modification enhanced the effect of Laves phase precipitation pinning and solid solution drag, which slowed the grain coarsening rate. With the modification of Al, the values of ultimate tensile strength, yield strength (0.2% proof stress) and total elongation increased compared to those of the Al-free alloys. The plasticity of the Al-modified alloys was improved with the retardation of sigma and chi phases at the grain boundary. This study provided valuable insights for the development of Al-modified ultra-super ferritic stainless steels with low precipitation brittleness tendency. [ABSTRACT FROM AUTHOR]

[Display omitted] • The nano-Y 2 O 3 reinforced ZK60 matrix nanocomposites are successfully fabricated via powder metallurgy. • The tensile properties of the 0.3Y 2 O 3 /ZK60 composites have improved a lot compared with the pure ZK60 alloy counterparts. • The addition of the nano-Y 2 O 3 particles can effectively refine grain and it also can hinder the movement of dislocations. • Molecular dynamics simulation results reveals the strengthening microscopic mechanism of Y 2 O 3 /ZK60 composites. The nano-Y 2 O 3 -reinforced ZK60 alloys are successfully prepared via powder metallurgy (PM) combined with hot-pressing sintering, and the effects of nano-Y 2 O 3 particle addition on the microstructure, corrosion resistance and mechanical properties of ZK60 alloys are studied. The results show that for the extruded samples, with the addition of nano-Y 2 O 3 particles to the ZK60 matrix, the average grain size is reduced to the nanoscale (750 nm), and the coefficient of thermal expansion (CTE) is decreased, with proper addition of nano- Y 2 O 3 particles can improve the strength, ductility and corrosion resistance meanwhile. The ultimate tensile strength and ductility of the extruded 0.3Y 2 O 3 /ZK60 composites are 336.5 MPa and 14.3 %, respectively. The increment in the ductility reaches 38.8 % relative to the initial ZK60 alloys, which achieves favorable strength plasticity product matching (U T = 4812 MPa%). However, excessive addition of nano-Y 2 O 3 particles and the agglomeration of nano-Y 2 O 3 particles around the grain boundary can lead to dislocation pinning and dislocation movement deterrence, but this also results in interface combination deterioration. The mainly contributions to the mechanical properties are grain refinement, dislocation strengthening and Orowan strengthening; Moreover, the molecular dynamics (MD) simulations results show the interaction of nano-Y 2 O 3 particle and dislocation is bypassing behavior. [ABSTRACT FROM AUTHOR]

[Display omitted] • The CT20 alloy with a special texture shows simultaneous improvement in strength and ductility at cryogenic temperature. • More twin types are activated at 77 K and continuous formation of twin boundaries causes the dynamic Hall-Petch effect. • The < -12–11>//ND texture and strong TWIP effect cause excellent ductility at cryogenic temperature. • Cryogenic temperature changed the locations of crack initiation in CT20 alloy with equiaxed microstructure. Quasi-static tensile deformation behaviors at room temperature (RT) and 77 K of the CT20 alloy with a <-12-11>//ND texture were investigated. The CT20 alloy with equiaxed microstructure exhibits excellent mechanical properties with simultaneous increase in strength and elongation at cryogenic temperature. In current study, the initial <-12-11>//ND texture promotes basal slip actuation effectively and continuously increases Schmid factor (SF) of other slip systems to promote multiple slip. Cryogenic temperature weakens the deformation texture due to the promotion of multiple slip. Since the decrease of the stacking fault energy (SFE), more twins in number and variety nucleate at 77 K and promote multiple slip. It causes strong cryogenic twinning-induced plasticity (TWIP) effect. Grain refinement induces strong cryogenic dynamic Hall-Petch effect resulting in high strain-hardening rate (SHR) and strength. The yield strength (YS, ∼1052.67 MPa), ultimate tensile strength (UTS, ∼1102.51 MPa) and elongation (EL, ∼21.1 %) of the 77 K specimen are about 84.1 %, 69.1 % and 38.8 % higher than its counterpart at RT, respectively. In addition, cryogenic temperature changes the initiation location of cracks and promotes cracks initiation at grain boundaries homogeneously. [ABSTRACT FROM AUTHOR]

[Display omitted] • The cellular boundaries are characterized by solute Nb segregation and high-density dislocations. • The cellular structure strengthening contributes significantly to YS. • The high HDI strengthening is the primary reason for the abnormal upturn of SHR. The unique cellular structure has been reported to be the dominant reason for the remarkable mechanical properties in laser powder-bed fusion (LPBF) superalloys. However, the specific strengthening mechanism of the cellular structure needs to be further researched. In this study, the microstructure and tensile properties of a composition-optimized Haynes 230 alloy fabricated by the LPBF method were systematically investigated. The post-heated HT1 and HT2 samples with different cellular and grain structures served as the reference. The results show that the micron-scale grain and submicron-scale cellular structures are present in the as-built (AB) sample. The cellular boundaries are characterized by solute Nb segregation and high-density dislocations. The tensile tests show that the AB sample illustrates excellent tensile properties with ultimate tensile strength (UTS) of 1180.2 MPa, yield strength (YS) of 842.5 MPa and elongation (EL) of 29.3 %. The high YS mainly results from the strengthening effects of the cellular structure, which can be considered as a combination of dislocation and elemental segregation strengthening. The contribution of cellular structure to YS is much higher than that of GB strengthening. Furthermore, the deformation incompatibility of heterogeneous grain and cellular structures leads to high hetero-deformation induced (HDI) strengthening, which is also the primary reason for the abnormal upturn of strain hardening rate (SHR) in the AB sample. [ABSTRACT FROM AUTHOR]

[Display omitted] • Low-cost high-mechanical ZA series alloys with the addition of MgCO 3 were successfully fabricated. • Mechanical properties of the alloys were greatly improved owing to the inoculation treatment. • Strengthening mechanisms of the alloys were analyzed by experimental and simulation methods. • The MnAl 2 O 4 phase could be used as an effective heterogeneous nucleation core of Mg matrix. In this work, the low-cost Mg-10Zn-1Al-0.5Cu-0.3Mn without or with the addition of MgCO 3 (labeled as S1 and S2 alloys) was successfully fabricated by a rapid-setting water-cooling method. The average grain size of the as-cast alloy decreased from 38.5 to 22.5 µm with the addition of MgCO 3. S2 alloy possessed excellent ultimate tensile strength and elongation of 275.6 MPa and 17.5 % in the solid solution state, which were approximately 21.6 and 82.3 % higher than those of the S1 alloy. The transmission electron microscopy results showed that the MnAl 2 O 4 phase with a high melting point was formed in the melt of S1 alloy by adding 1 wt% MgCO 3 , which had a phase relationship of (1 0 1)Mg||(3 1 1)MnAl 2 O 4. Additionally, the results of edge-to-edge matching model showed that the MnAl 2 O 4 phase tended to grow on the Mg matrix phase. The results of the first-principles calculations exhibited that the (1 0 1)Mg||(3 1 1)MnAl 2 O 4 interface with MnO terminations was a strong interface. The MnAl 2 O 4 phase could be regarded as heterogeneous nucleation points to improve the nucleation rate and thus to refine the grain and enhance the strength. This study can vigorously provide a certain guide for the grain refinement of Mg-Zn based alloys containing Mn. [ABSTRACT FROM AUTHOR]

Abstract NGCs are considered as an alternative treatment method for treating peripheral nerve injuries in place of nerve autografts. Biomimicry, conductivity, and biodegradability are the properties expected of an ideal NGC. PCL/PAA NGCs with three different concentrations of PAA (2.5, 5 and 7.5%) were fabricated using EHD-jet 3D printing. The mechanical properties of the PCL/PAA NGCs mimic the native human nerve properties (ultimate tensile strength of 6.5 to 11.7 MPa) and the conductivity match that of the amphibian motor nerve fiber myelin sheath (10−6 S/cm). The in vitro degradation studies reveal that they are biodegradable and injury/site-specific biodegradability can be obtained by tuning the PCL/PAA concentration ratio. In addition, PAA being a polyanionic polymer has the potential to act as a cation-exchanger, mimicking the functions of the nerve cortical gel layer, thereby influencing the electrophysiological phenomena called nerve excitation and conduction. Neural differentiation studies with PC12 cells assessed by the Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and immunocytochemistry showed enhanced gene expression with the presence of PAA. Our results suggest that the EHD-jet 3D printed porous conductive PCL/PAA NGCs has the potential to be used in the treatment of peripheral nerve injuries. Graphical abstract Unlabelled Image Highlights • Ideal Nerve Guide Conduits with biomimicry and conductivity were fabricated using Electrohydrodynamic Jet 3D Printing • The mechanical properties and conductivity of the scaffolds mimic the native human nerve properties • Poly(acrylic acid) as cation-exchanger mimics nerve cortical gel layer functions, influencing nerve excitation & conduction • PC12 in vitro neural differentiation studies showed enhanced gene expression with the presence of Poly(acrylic acid) • Can potentially be used to treat peripheral nerve injuries & neurodegenerative conditions (Alzheimer's and Parkinson's) [ABSTRACT FROM AUTHOR]

Abstract The strength and plasticity of metallic materials usually exhibit a trade-off relation. This study reports a simultaneous improvement in the ultimate tensile strength (UTS) and uniform elongation (UE) of Ti-24Nb-4Zr-8Sn (Ti2448) fabricated by selective laser melting (SLM), relative to those produced via forging. Detailed microstructural characterization reveals that the outstanding tensile property may result from the bi-model structure that forms during the rapid cooling associated with SLM. Coarse grains are surrounded by fine grains within the melt pool, which causes a back stress during tension. The back stress provides additional strain-hardening capacity, which postpones the initiation of necking and then leads to the simultaneous improvement of the strength and plasticity (SISP) of the Ti2448 alloy. Furthermore, the tensile property of the SLM-fabricated sample is anisotropic which is strongly related to the irregular shape of the melt pool. Graphical abstract Unlabelled Image Highlights • Melt pools with a bi-model structure are formed in a biocompatible Ti alloy through selective laser melting. • The as-built Ti alloy exhibits a better combination of strength and plasticity, relative to traditionally forged counterpart. • For the first time, the back stress of the melt pool along different directions is studied through finite element modelling. [ABSTRACT FROM AUTHOR]

In recent time, cold spray additive manufacturing (CSAM) has emerged as a promising solid state manufacturing technique to produce thick deposits of pure metal, alloys and composites with limited risk of oxidation, phase transformations, and residual thermal stresses. This preliminary study highlights an effective post spray thermo-mechanical treatment (TMT) that can be used to efficiently heal out splat boundaries and rejuvenate mechanical properties of the as-sprayed composites. CSAMed B 4 C/Al composite was subjected to a series of TMTs via heating at ~500 °C in the furnace for 2 h followed by unidirectional rolling treatments with thickness reductions of 20, 40 and 60% in 1, 2 and 3 passes, respectively. Microstructural investigations revealed that as the thickness reduction was increased from 20%, matrix grains were extensively refined due to continuous dynamic recrystallization (CDRX). Moreover, bonding between Al/Al splats and B 4 C/Al interfaces was remarkably improved due to enhanced inter-particle diffusion activity. Consequently, yield strength (YS), ultimate tensile strength (UTS) and elongation (EL) of the as-sprayed composite were enhanced simultaneously. The TMTed sample with thickness reduction of 60% showed highest values of UTS and EL compared with the corresponding values of as-sprayed and conventionally heat treated samples. [ABSTRACT FROM AUTHOR]

Abstract: Double control forming technology was firstly proposed for meeting the producing requirements of complex Mg alloy parts with high mechanical properties. Not only the high-speed filling but also high-pressure densifying and refining could be achieved in double control forming technology. A typical part of motorcycle cylinder body was used for demonstrating its advantages. The results showed that complete filling could be achieved by injection system of double control forming device and the microstructure of formed part was densified and refined well by its forging system. High mechanical properties such as ultimate tensile strength of 241MPa and elongation of 13.9% were achieved in the parts formed by double control forming. Compared to die casting, the ultimate tensile strength was increased by 63.9% and elongation was increased by 3.3 times. A large number of fine equiaxed grains with the average size less than 20μm were found in the microstructure of parts formed by double control forming. A refined microstructure also led to a more uniform distribution of primary equiaxed grains and second phase. Casting defects such as shrinkage voids were removed from the microstructure due to the forging pressure. [Copyright &y& Elsevier]