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In this paper, the effects of cyclic deep cryogenic treatment (CDCT) on the mechanical properties and the precipitated phases evolution of 7B55 aluminum alloy produced by wire arc directed energy deposition (WA-DED) were systematically investigated. The findings revealed that, under both T6 and CDCT conditions, the microstructure of the 7B55 aluminum alloy exhibited fine-equiaxed grains. Under the T6 condition, the precipitated phases within the grains were primarily composed of clustered GP zones and η ′ phases. Meanwhile, the η phases were continuously distributed along the grain boundaries. Upon subjecting the material to three cycles of CDCT, a noticeable reduction in the number of GP zones within the grains was observed. Simultaneously, there was a substantial increase in the number of η ′ phases, accompanied by the occurrence of dislocation lines. The distribution of η phases along the grain boundary transitioned to an interrupted pattern. Under the CDCT-Cycle 3 (CDCT-C3) condition, the ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) achieved 658.6 ± 4.5 MPa, 624.2 ± 5.2 MPa, and 8.42 ± 0.18 %, respectively. However, with the progression to four cycles of CDCT, the GP zones within the grains disappeared and the number of η ′ phases started to decrease with the formation of a large number of η phases. The η phase along the grain boundary continuously grew by merging and absorbing solute atoms from the Al matrix near the grain boundaries. This led to the formation of coarsen and interrupted η phases and the Precipitate-Free Zone (PFZ) along the grain boundaries. Subsequently, the mechanical properties experienced a substantial decrease after the CDCT-Cycle 4 (CDCT-C4). • The effect of CDCT on the evolution of precipitated phases WA-DED Al–Zn–Mg–Cu alloy was investigated. • The number of η ′ phase and the dislocation density within grains were increased after CDCT-C3. • The η phases along grain boundaries were changed to interrupted distribution and PFZs were formed after CDCT-C4. • The UTS reached 658 MPa and a breakthrough was achieved among WA-DED aluminum alloys. [ABSTRACT FROM AUTHOR]

The uncontrollable directional grain growth and non-equilibrium microstructure of Inconel 718 will form during laser direct energy deposition (LDED), which seriously limits the promotion and application, so it is necessary to consider the heat treatment to improve the microstructure and mechanical properties. In this paper, the effects adopting different heat treatments on the phase composition, precipitation behavior, grain structure, tensile and tribological properties of LDED Inconel 718 have been systematically investigated, with as-deposited samples compared. The results show that the number and size of γ″ phases can be significantly changed under different aging and solution conditions, and the strength and wear resistance increase while elongation decreases since the fine grain and precipitation strengthening occurring during heat treatment. By comparing the different samples, the SA1100A exhibits the highest yield and tensile strength, with 140.6% of yield strength and 83.9% of ultimate tensile strength increasing compared to as-deposited samples, also showing the narrowest wear mark width and the lowest average mass loss. [ABSTRACT FROM AUTHOR]

The effects of Mn content on the Sn distributions, grain sizes, second phases, and mechanical properties of Cu–9Ni–6Sn- X Mn alloys (wt.%, X = 0, 0.1, 0.5, and 1.0) were studied in this paper. The mechanisms of acting and strengthening through which Mn could promote grain refinement in the alloy were discussed. The results showed that the addition of Mn transforms the as-cast microstructure of the alloy into equiaxed grains, and the grains are obviously refined. When the amount of Mn is approximately 0.1 wt%, the average grain size of this alloy is 91.75 μm, and the grain refinement effect is greatest in the experimental range. In addition, Mn increases the uniformity of the distribution of Sn in the as-cast microstructure. Differential scanning calorimetry (DSC) analysis revealed that the addition of Mn increases the undercooling of the as-cast Cu–9Ni–6Sn alloy and decreases in the critical nucleation radii of the grains. Further microstructure observation showed that Mn is dissolved mainly in the γ-(Cu,Ni) 3 Sn phase. Consequently, the interfacial relationship between the γ-(Cu,Ni) 3 Sn phase and the matrix transforms from incoherent to semicoherent. Compared with those of the Cu–9Ni–6Sn alloy, the strength and elongation of the alloy with added Mn are relatively great. When the content of Mn is 0.1 wt%, the strength of the alloy increases from 359.75 MPa to 423.54 MPa, while the elongation remains at 19.14 %. The synergistic effect of solution strengthening and fine grain strengthening of Mn is the main reason for the great improvement in the mechanical properties of the alloy. [ABSTRACT FROM AUTHOR]

Ti–22Al–25Nb alloy is a lightweight, high-performance, and high-temperature material with broad application prospects in aerospace. Laser powder bed fusion (LPBF) enables the rapid manufacture of Ti–22Al–25Nb (at. %) powder into complex, high-precision parts for various applications. This paper provides an in-depth analysis of how scanning speed affects the microstructure and mechanical properties of Ti–22Al–25Nb alloy prepared by LPBF. The goal of this study is to improve the mechanical properties and the printing efficiency in the future. The temperature distribution in the printing process was studied by finite element simulation, and the effect of scanning speed was analyzed by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The results show that increasing the scanning speed improved the cooling rate of the liquid melt, which decreases the grain size of the β phase and increases of the dislocation density. At the same time, a significant amount of the O phase precipitates along the grain boundaries. Excellent elongation (15%) and yield strength (982 MPa) are obtained due to the pinning of the nano-O phase, a fine grain, and good relative density when the scanning speed is 0.6 and 0.8 m/s, respectively. [ABSTRACT FROM AUTHOR]

Abstract Given the transformation stasis after the incomplete transformation of carbide-free bainite, this paper aimed to study the effects of austempering time within transformation stasis on the bainite microstructure, monotonic deformation behavior, and especially cyclic deformation behavior using an ultrahigh silicon (2.59 wt%) steel. With increasing austempering time, the dislocation density of bainitic ferrite decreased, carbon content of retained austenite slight increased, and carbon distribution in retained austenite blocks gradually homogenized. The best combination of strength and ductility was obtained through a longer austempering time within transformation stasis. But the longer austempering time, indeed, did not result in longer fatigue life. The opposite trend could be explained by the fact that the primary factors affecting these mechanical properties were different. The lower density of mobile dislocation pre-existed in the starting microstructure of the samples austempered for a longer time was primarily responsible for its lower cyclic hardenability. Moreover, one retained austenite block with completely homogeneous carbon distribution was only transformed to one martensite grain, which increased the cyclic softening and degrade the fatigue life. By contrast, the deformation-induced martensite transformation from the retained austenite with higher mechanical stability in the samples austempered for a longer time enhanced strain hardenability at higher monotonic tensile strains and well delayed the necking, thus improving the combination of strength and ductility. [ABSTRACT FROM AUTHOR]

Abstract Shortening the bainite transformation time is one crucial issue on the application of high carbon nano-bainite steel. In this paper, an accurate black-box model that could predict the plate thickness of bainitic ferrite was constructed based on gradient boosting decision tree model, and a polynomial model was constructed to make predicting process easier. According to the constructed model, a two-steps process was proposed, which shortened the transformation time from over 60 h to nearly 25 h. After the new process treatment, the size distribution of bainitic ferrite in microstructure became more uniform, and the strength and toughness of steel were also improved simultaneously. [ABSTRACT FROM AUTHOR]

Abstract In this paper, dual-scale Ti-6Al-4V titanium alloys were prepared by cryomilling and plasma activated sintering. The microstructure and mechanical properties of the samples with different structural organizations were investigated. The relative densities were evaluated by the drainage method. The microstructure and mechanical properties were characterized by OM, SEM, XRD, EBSD, TEM, universal testing machine and Vickers hardness test methods. The results show that the dual-scale Ti-6Al-4V titanium alloy with high strength can be prepared in a relatively short time by cryomilling and plasma activated sintering. The scale structure of the alloy is controlled by a relative amount of ball-milled powders. With the ball-milled powder content increases, the fraction of the β phase and the axial fine crystalline region is increasing. The dual-scale structure renders and the mechanical properties of the samples are more superior to the coarse crystal samples. In addition, the plastic deformation capability of the dual-scale structure is better than that of fine crystal samples. A relative density of 98.54%, the enhanced mechanical properties, including offset yield strength of 1544.19 MPa and a Vickers hardness of 427 HV were achieved, which is attributed to the different dual-scale structures. [ABSTRACT FROM AUTHOR]

Here, cold-drawing was applied to melt-extracted Cu 47.5 Zr 47.5 Al 5 amorphous alloy (AA) microwires. The structural observations and tensile deformation behaviors were studied before and after cold-drawing. The drawn wire still possesses amorphous structure. Less surface defects, higher local order degree, and greater compressive residual stress induced by cold-drawing lead to a higher tensile fracture strength and a higher reliability of the drawn wires than those of melt-extracted one. The results obtained in this paper demonstrate that the cold-drawing processing is an effective method to improve the mechanical performance of the AA wires. • Cu 47.5 Zr 47.5 Al 5 alloy wire remains its glassy structure after cold-drawing processes. • Residual stresses during drawing process lead to a local disorder-order transition. • Tensile fracture strength and reliability of the alloy were enhanced by the drawing. [ABSTRACT FROM AUTHOR]

In this paper, the grain size effect on martensite transformation and its mechanical properties were investigated in two high-carbon steels. The results show that grain refinement can induce a phase transformation of high carbon martensite substructure from twin to dislocations. When grains are refined to smaller than 4 µm, no twin could be observed, instead, full dislocation substructure is obtained. And the martensite substructure transition results in an enhancement in mechanical properties, an ultrahigh tensile strength of 2.28 GPa and a significant elongation of 6.8% are obtained in the 0.61 wt%C steel. A model based on the relationship between dislocation slip stress ( τ S ) and twin shear stress ( τ T ) with grain size ( d ) is developed to explain the above phase transformation phenomenon. The τ T is proportional to d − 1 and τ S is proportional to d −1/2 , both of which increase with reducing grain size, but τ T is more sensitive to grain size. Therefore, a critical grain size ( d c ) is obtained, at which the stresses for twining and for dislocation gliding are equal, lower than this value (i.e. grain is finer), the stress for twin is higher than that for dislocation gliding, so dislocation slip becomes main deformation process in martensite transformation. The theoretically calculated d c is about 2.7–7.6 µm, which is in good agreement with the experimental results. These findings may provide a new way to design ultra-high strength and high ductility steels. [ABSTRACT FROM AUTHOR]

The nanostructured bainitic (NB) bearing steel exhibits excellent rolling contact fatigue (RCF) resistance, which is critical to the service of bearing. However, the detailed microstructural evolution of the steel during the RCF process is still unclear. In this paper, a carburized NB bearing steel was studied and a detailed process investigation on microstructural evolution of the steel during the RCF progress was carried out. Results show that the nano-sized bainitic ferrite is gradually refined, and the undissolved carbide s gradually flake away and some of them remain in solution during the RCF process. It is interesting to find that there are three stages for the martensitic transformation of retained austenite. During the first stage of 0–0.48 × 10 7 cycles, nearly all of the block-like retained austenite in the top surface transforms into martensite rapidly, and during the second stage of about 0.48–1.92 × 10 7 cycles, nearly no retained austenite further transforms into martensite, but when the fatigue exceeds the 1.92 × 10 7 cycles, the film-like retained austenite gradually transforms into martensite at a slow rate. The transformed martensite not only increases the surface hardness but further brings additional residual compressive stress in surface layer. It is analyzed from the microstructure characterization along the longitudinal section of the fatigue specimen that the fatigue crakes are initiated at subsurface of specimen, which propagate up to the surface and finally result in fatigue flake. [ABSTRACT FROM AUTHOR]

In this paper, graphene oxide (GO)/Cu composite (GO/Cu) foils with high thermal and mechanical properties were prepared by ultrasonic-assisted direct current electrodeposition. The effect of ultrasonic power and graphene concentration on the microstructure and properties of the composite foils was systematically investigated. It was found that the average grain size can be refined by both the addition of GO reinforcement and ultrasonic treatment. Under the optimized preparation condition with 120 W ultrasonic power and GO concentration of 0.8 g/L GO in plating solution, the average grain size was about 0.26 μm and illustrated strong crystallographic orientation of (220). In addition, the GO content in the composites was increased from 0.67 wt% without ultrasonic treatment to 1.72 wt%, and it was uniformly dispersed in the composite foil with ultrasonic effect. Compared with pure copper foil, the hardness value of the GO/Cu composite foil nearly doubled to 74.6 HV 0.1 , the average friction coefficient was decreased from 0.87 to 0.72 and the tensile strength of the composite foil was improved to 239 MPa with an elongation of 17%. Meanwhile, the thermal conductivity with optimized condition increased 39.8% to 556.57 W m−1 K−1. The improved mechanical and thermal properties of the GO/Cu composite foil were mainly ascribed to the grain refinement, change of preferred orientation and the presence of reduced GO reinforcement as a network in the composite foil. • The thermal and mechanical properties of GO/Cu composite simultaneously improved by ultrasonic-assisted electro-deposition. • The GO content in the composites is increased and the grain size is refined. • RGO was uniformly distributed at the grain boundaries of the composite, forming a continuous network structure. [ABSTRACT FROM AUTHOR]

In this paper, in-situ nanoparticles ZrB 2 and Al 2 O 3 are introduced to raise the mechanical properties of AA7N01 Laser beam welding (LBW) joint by in-situ melt reaction method. The effects of ZrB 2 and Al 2 O 3 nanoparticles on the microstructure and tensile properties of in-situ (ZrB 2 +Al 2 O 3)/AA7N01 nanocomposites and LBW joints were studied. The experimental results indicate that ZrB 2 nanoparticles provide more nucleation sites for grain nucleation and tend to aggregate at the grain boundary (GB). The average grain size of composites is greatly refined from about 110 μm to 20 μm. As the content of particles increased from 1 vol% to 3 vol%, the ultimate tensile strength (UTS) of nanocomposites is enhanced from 439.3 MPa to 538.2 MPa, the UTS of the LBW joint is increased from 246.7 MPa to 353.6 MPa. The effects of ZrB 2 and Al 2 O 3 nanoparticles on grain refinement and growth of matrix are analyzed. Furthermore, the strengthen mechanism induced by the precipitates and nanoparticles on the mechanical properties of composites and joints are also discussed. • The ZrB 2 and Al 2 O 3 nanoparticles were introduced into composites. • Grain refinement and mechanical properties improvement of Al alloy by ZrB 2 and Al 2 O 3 nanoparticles had been displayed. • Laser beam welded joints were prone to fracture in heat-affected zones. • The UTS of 3 vol% (ZrB 2 +Al 2 O 3)/AA7N01 LBWed joint was 353.6 MPa higher than that of AA7N01 LBWed joint. [ABSTRACT FROM AUTHOR]

This paper addresses the microstructure-properties relationship during resistance spot welding of martensitic stainless steel (MSS). The effect of the initial base metal microstructure (ferritic microstructure in annealed condition vs. partially tempered martensitic in quench and tempered condition) on the weld microstructure evolution is highlighted. Regardless of the initial base metal microstructure, the fusion zone exhibited a predominantly martensitic structure plus some δ-ferrite. The heat affected zone (HAZ) in the quenched and partially tempered (Q-PT) sheet was featured by formation of martensite and carbide in upper-critical zone and tempering of martensite in sub-critical zone. The latter caused pronounced softening in the HAZ compared to the base metal. However, the HAZ in the annealed sheet exhibited hardening compared to the base metal due to the formation of a dual phase microstructure composed of martensite plus carbide. Nor high strength mismatch between fusion zone and base metal (when welding in the annealed condition), neither severe HAZ softening (when welding in the Q-PT condition) did not promote pullout failure mode. The consistently predominant interfacial failure of the MSS welds was governed by the low fracture toughness of the fusion zone. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) and laser cladding deposition (LCD) are two typical kinds of laser additive manufacturing techniques that have been developed for many years independently. Although they are based on the same principle of laser cladding, there are little comparison on the fundamental studies for metallurgical behavior (including melting and solidification behaviors) and the mechanical properties of these two techniques up to now. In this paper, the single-track formation and the deposition of block sample from 316L stainless steel powders have been carried out by both SLM and LCD techniques. A comparison on pool shape, cooling rate, columnar grain size and mechanical properties under different processing conditions by LCD and SLM respectively has been studied. It is found that, due to the increase of energy input and the decrease of depth-to-width ratio of melting pool (MP) from SLM to LCD, the primary cellular arm spacing (PCAS) of the sample increases from less than 1.0 µm to more than 15.0 µm, and thus the cooling rate of MP decreases from about 10 6 K/s in SLM to about 10 2 K/s in LCD. Furthermore, due to the decrease of cooling rate from SLM to LCD, the columnar grains of the as forming alloy are getting coarser. Especially, the relationship between gain size (λ) and the reciprocal of square root of cooling rate ( T ̇ ) in LCD significantly meets the classical linear function of λ = a + b / T ̇ ( a and b are constants), while a new relationship of a cubic function is found in SLM, showing the different solidification characteristics between LCD and SLM. Lastly, the samples of 316L stainless steel by SLM have much stronger tensile strength but lower elongation than those by LCD, and the main reason is due to that the solidification behavior of the MPs by SLM can form much finer columnar grains than those by LCD. [ABSTRACT FROM AUTHOR]

In this study, the microstructural evolution and mechanical properties of Al-Li 2198-T8 (artificially peak aged) separately processed by two typical severe plastic deformation (SPD) methods (i.e. friction stir processing (FSP) and high-pressure torsion (HPT)) were investigated. The microstructural examination showed that both FSP and HPT were capable of refining the grains for Al-Li 2198-T8, and the HPT processing produced much finer grains. Transmission electron microscopic observation revealed that precipitates of β′ (Al 3 Zr), θ′ (Al 2 Cu) and T1 (Al 2 CuLi) existing in the as-received Al-Li 2198-T8 fully dissolved after HPT, whereas the precipitates of β′ (Al 3 Zr) were retained in the processed zone after FSP. The hardness and tensile testing demonstrated that the hardness and strength of FSP-processed alloy significantly declined compared to the as-received alloy, while those of HPT-processed alloy substantially increased due to exceptional grain refinement and high dislocation density. The strengthening mechanisms of the alloy before and after the SPD processing were discussed in the present paper. [ABSTRACT FROM AUTHOR]

To develop ultra-heavy high strength plate with outstanding strength homogeneity in thickness direction, a novel method called gradient temperature rolling (GTR) process followed by intercritical quenching and tempering was employed in this paper, and the mechanism for GTR process on the microstructure, mechanical property and fracture mechanism were investigated. The results showed that, GTR process could effectively refine prior austenite grain size in half and quarter thickness of as-rolled plate, and increase the fraction of intercritical ferrite and high angle boundaries in as-quenched specimens. The ultra-heavy plate with yield strength of 690 MPa was developed by GTR and represented excellent mechanical property, such as the elongation and −40 °C impact energy are more than 16% and 60 J, respectively, and the maximum difference of yield strength was less than 10 MPa in full thickness indicating that an outstanding strength homogeneity was achieved. By further analysis of macroscopic and microscopic impact fracture, the cracks in plate produced via conventional uniform temperature rolling process are mainly orginated from large, sharp-cornered M/A islands. However, the cracks of plate produced by GTR process are primarily initiated around precipitates, packet boundaries and ferrite-tempered martensite interface, and propagate by microvoid growth, coalescence and microvoid linkage, which leads to the excellent low temperature toughness. [ABSTRACT FROM AUTHOR]

Friction stir welding (FSW) of dissimilar joints has recently attracted great interest for the fabrication of bimetallic and layered composite structures. In this paper, dissimilar joining of an aluminum-matrix hybrid nanocomposite to commercial pure aluminum is reported for the first time. An aluminum hybrid nanocomposite reinforced with Al 2 O 3 (2 vol %; 15 nm) and SiC (2 vol %; 50 nm) nanoparticles was prepared by powder metallurgy routes including mechanical milling and hot powder consolidation techniques. Different joint designs at various ranges of rotational ( w ) and traverse velocities ( v ) were evaluated to determine process window for the dissimilar solid-state welding. Macro- and micro-structural studies showed that sound joints, which were free of voids, cracks or un-bonded areas, could be attained by applying w =1200 rpm and v =50 mm/min, while locating the nanocomposite at retreating side. Optical microscopy revealed that the stir zone consisted of micro-scale mechanical inter-locks. Mechanical characterization indicated that the mechanical properties of the dissimilar joint were superior to that of commercial aluminum but lower that of the hybrid nanocomposite by an order of 128–70% (in terms of tensile strength) and 135–70% (hardness). Fractographic analysis showed a ductile fracture mode around the interface of aluminum/stir zone and a combined ductile-brittle fracture mode for the interface region of the nanocomposite/stir zone. The role of nano-scale hard particles on the weldability, microstructural development, mechanical strength, and fracture behavior was elaborated. [ABSTRACT FROM AUTHOR]

In this paper, friction plug welding (FPW) experiments of 2219-T87 aluminum alloy sheets with 10 mm thickness were performed. The material flow behavior, microstructures, second phases, mechanical properties and failure behaviors were also investigated. The results indicate that a sufficient volume of material from both plug and base metal flow upward and downward is critical obtaining defect free weld. The plug thermo-mechanically affected zone, plug recrystallized zone, thermo-mechanically affected zone (TMAZ), and heat affected zone could be weakened significantly owing to the thermal–mechanical process. The main reason is believed as the dissolution of precipitates and the redistribution of constituent particles. The maximum tensile strength and elongation of the joint would reach 329 MPa and 7%, respectively. The TMAZ closest to the bonding interface is the weakest location of the joints. The tensile crack initiates at TMAZ close to the bonding interface near the lower surface and then propagates along the soften area in TMAZ with forming a large amount of dimples with second phases existing at the bottom. [ABSTRACT FROM AUTHOR]

Effect of intermediate annealing on the microstructure, texture and mechanical properties of Al–Mg–Si–Cu alloy sheet in the different conditions was investigated by means of tensile test, microstructure characterization and texture measurement in this study. The results show that, three different intermediate annealing treatments (no annealing, low temperature annealing, high temperature annealing) have a great influence on the evolution of microstructure and texture, and final mechanical properties. Compared with the high temperature annealing and no intermediate annealing, the low temperature annealing is most beneficial to improve mechanical properties, especially for improving the average Lankford coefficient r and reducing Δ r values, and to form the uniform recrystallization structure and the finer recrystallization grains. Although the intermediate annealing temperature only affects the intensities of textures formed by annealing treatments, and the intensities of β fibers formed by the following cold rolling, yet, the texture components are quite different in the three alloy sheets in the T4P state, and only the Cube ND orientation produced by PSN effect appears in the alloy sheet treated by the low temperature annealing. Additionally, the relationship between texture, r value and yield strength was analyzed by VPSC model and slip theory in this paper. [ABSTRACT FROM AUTHOR]

The effect of heating rate on the mechanical properties, microstructure and texture of Al–Mg–Si–Cu alloy during solution treatment was investigated through tensile testing, scanning electron microscope, scanning transmission electron microscope, metallographic observation and EBSD measurement. The experimental results reveal that there are great differences in the mechanical properties, microstructures and textures after the solution treatment with two different heating rates. Compared with the alloy sheet solution treated with slow heating rate, the alloy sheet solution treated with rapid heating rate possesses weak mechanical property anisotropy and higher average r value. The equiaxed grain is the main recrystallization microstructure for the case of rapid heating rate, while the elongated grain appears in the case of slow heating rate. The texture components are also quite different in the two cases, Cube ND orientation is the main texture component for the former case, while the latter one includes Cube, R, Goss, P and Brass orientations. The relationship between r value, texture components and microstructure has also been established in this paper. [ABSTRACT FROM AUTHOR]

In this paper, high power laser powder bed fusion (HP-LPBF) of AlSi10Mg alloy was conducted under the conventional level layer thickness (0.05 mm) and the sub-millimeter level thickness (0.10–0.25 mm). The effect of layer thickness on defect, microstructure and mechanical property of the HP-LPBF AlSi10Mg alloy are studied. The results first demonstrate that the relative density of the HP-LPBF sample is higher than 99.8% when the layer thickness is 0.05–0.10 mm and decreases monotonously with the layer thickness increasing from 0.05 to 0.25 mm. Then, it is found that all the HP-LPBF samples possess a cellular structure composed of α-Al matrix and eutectic Si. However, the crystallographic features are significantly influenced by the layer thickness. When the layer thickness is only 0.05 mm, the α-Al matrix is mainly composed of columnar grains with <100> orientation parallel to the build direction. With the increase of layer thickness, the growth direction of the columnar grains becomes diversified whilst the proportion of the equiaxed grains increases, resulting in the decrease of <100> texture intensity. Finally, it is shown that the tensile property of the HP-LPBF sample presents a V-shaped relationship with the layer thickness. Except the minimum value which is obtained at the layer thickness of 0.20 mm, the tensile properties of the HP-LPBF samples are superior to that of the die-casting AlSi10Mg. The relevant influence mechanisms are also revealed. [ABSTRACT FROM AUTHOR]

High-Mn steels exhibit both high tensile strength and good ductility and have attracted much attention as a promising candidate for next-generation automotive steel. However, there are still problems in conventional production, such as severe slab crack and pronounced element segregation, which restrict their widespread applications. An alternative way to produce this alloy is the near net shape method under a sub-rapid solidification process. We studied the microstructure and mechanical properties of Fe-18Mn-(0.14, 0.50)C alloy thin strip produced by injecting casting at a sub-rapid solidification rate, in which the cooling rate was about 5x10=sup=3=/sup=K/s. The results demonstrated that the formation of cementite particles was suppressed, but apart from the γ-phase, the ε-martensite and α'-martensite also formed in the Fe-18Mn-C thin strips. The lath width of ε-martensite is lower than that of sample produced by conventional method. The mechanical properties of Fe-18Mn-0.50C surpass the Fe-18Mn-0.60C alloy steel processed by hot rolled and heat treated. This paper discusses the relationship between the microstructure and the mechanical properties of the strips. [ABSTRACT FROM AUTHOR]

Abstract: Steel foams can be used as lightweight and high-functional materials in applications such as transport vehicles, machines and structural parts due to their low cost, high strength, high heat resistance and good weldability. In this paper, low alloy steel foams (Fe–1.75Ni–1.5Cu–0.5Mo–0.6C) having porosities in the range of 47.8–70.9% with different pore sizes were produced by the space holder-water leaching technique in powder metallurgy. The structural and mechanical property variations resulting from the use of spacer particles having different amounts and sizes were investigated. Irregular carbamide particles were used as spacer. The porosity and pore size of steel foams replicated the initial amount and size of the spacer. Visual inspections were performed for the coated spacers having different sizes and amounts with steel powders after the final mixing. The amount and size of spacer determined the coatability of the mixtures. A decrease in pore size improves the strength of the steel foams by sharing the load with more and smaller pores; however, small pores having the highest porosity can impair the strength because no enough metals hold the integrity of the new pore walls. The influence of pore size on stress drop ratio of steel foams was also studied. The stress drop ratio decreased with decreasing porosity of steel foams. In addition, an increase in pore size caused a bigger stress drop ratio. However, the highest stress drop ratio was determined for small pores having the highest porosity due to the interconnection of macropores in the foam structure. [Copyright &y& Elsevier]

Abstract: In this paper, the ageing response and the mechanical properties of Ti-5553 (Ti–5Al–5V–5Mo–3Cr) and Ti-5553s (Ti–5Al–5V–5Mo–3Cr–0.4Si) alloys are comparatively investigated. During ageing at 650°C, the hardness of the alloys first increases in 30min and remains constant from 1h to 8h, and then decreases with further increase the ageing time to 29h. This variation is related to the chemical composition and the volume fraction of α phase. The mechanical properties of the 5h aged Ti-5553 and Ti-5553s alloys are investigated, and the result shows that the ultimate tensile strength of the Ti-5553s alloy is higher than that of Ti-5553 alloy while the ductility of the Ti-5553s alloy slightly decreases. The tensile fracture of the Ti-5553s alloy shows a mixed model of intergranular fracture and cleavage fracture. [Copyright &y& Elsevier]

Abstract: The purpose of this paper is to investigate the influence of non-uniform precipitate distribution on local plastic deformation in HIPed P/M nickel-base superalloy FGH96 by using micro-indentation methods. The micro-indentation tests were conducted in the indenter load range from 100mN to 450mN and the loading rate range from 1.94mN/s to 19.37mN/s at the room temperature. Then, the load–displacement data of precipitate concentration areas (PCA) and precipitate sparsity areas (PSA) were obtained, respectively. The results show that both PCA and PSA exhibited decreasing micro-hardness during indentations, which proved that the size effect was significant in P/M nickel-base superalloy FGH96 as well. The high micro-hardness of PCA indicates that γ′ precipitate could effectively improve the resistance to deformation. In contrast, the influences of indenter load and loading rate on Young’s modulus were slight. Through plotting test data, it was revealed that a better linear relationship existed between H 2 and 1/h. Moreover, the densities of geometrically necessary dislocations (GNDs) and statistically stored dislocations (SSDs) were obtained by data fitting. Like other alloys, the GND density fast decreased with the increase of indentation depth during indentations. The SSD density of PCA was higher than that of PSA when the loading rate was lower than 12.91mN/s, indicating that the γ′ precipitates could block the dislocation movements and induce strong interactions. However, this mechanism was inconspicuous at high loading rates due to precipitation shearing mechanism. In addition, the FEM method and forward analysis algorithms were used to predict the micro-indentation parameters. Comparing with FEM method, the prediction results were more accurate for forward analysis algorithms. The constitutive equations of PCA and PSA were established by means of reverse analysis algorithms. The microstructural simulation reflected that the interactions between PCA and PSA were significant during uniaxial compression. The high stress concentration existing in PCA between two adjacent PSAs may cause microcracks and void dislocations at the large deformations. [Copyright &y& Elsevier]

Abstract: The aim of this paper is to investigate the static and dynamic mechanical properties of concrete before and after high temperature exposure. Quasi-static and impact loading experiments were carried out on concrete before and after exposure to the temperature of 200–800°C by using a servo-hydraulic testing machine and a 100-mm-diameter split Hopkinson bar (SHPB) apparatus, respectively. The results show that, mechanical properties of concrete after high temperature exposure change evidently, and the critical temperature for those changes acquiring dramatic character is 400°C. With the rise of temperature up to 400°C, compressive strength and critical strain change little compared with that of at room temperature. While with temperature increasing from 400 to 800°C, the decrease in strength and the increase in critical strain become obvious. Consequentially, specific energy absorption (SEA), which is the synthetic exhibition of strength and ductility, decreases much less than those observed for strength over 400°C. Dynamic compressive mechanical properties of concrete before and after high temperature exposure increase with the rise in strain rate rapidly, which exhibits strong strain rate dependency. Dynamic increase factor (DIF) increases approximately linearly with strain rate. In a word, concrete can be recognized as an excellent thermal-resistant and anti-impact construction material. [Copyright &y& Elsevier]

Abstract: In this paper, split dies combined with a spring-loaded auto-fastening system are newly proposed to continuously apply an equal channel angular pressing (ECAP) process to a multi-pass bolt forming process. The proposed spring-loaded ECAP set-up was used to produce microstructure-refined materials in a continuous manner. Experiments for a single pass of the ECAP followed by four stages of the bolt forming process were carried out to manufacture a microstructure-refined bolt made of an aluminum alloy 6061 by using the multi-stage former at room temperature. The present study clearly showed that manufacturing the microstructure-refined bolt is possible with the proposed die set-up with a conventional material. The proposed process design might be beneficial in using the ECAP as part of a continuous process sequence to increase the mechanical strength of the material without adding more alloying elements in industry. [Copyright &y& Elsevier]

Abstract: This paper presents the successful preparation of a high-damping, high-strength Mg–Cu–Mn–Zn–Y alloy by alloying and extrusion. The damping capacity of the as-cast Mg–3Cu–1Mn alloy (alloy 1) displayed evident variations with changes in Y and Zn content. The as-cast Mg–3Cu–1Mn–2Zn–1Y alloy (alloy 2) exhibited excellent damping capacity and unusual damping growth in the high-strain amplitude stage; the damping capacity of alloy 2 exceeded that of alloy 1 and even approached that of pure Mg when the strain amplitude exceeded 5×10−4. This observation is believed to be related to the formation of long and parallel dislocation configurations and the interactions between these dislocations and plastic second-phase particles. The study also showed a remarkable improvement in the mechanical properties of as-extruded Mg–Cu–Mn–Zn–Y alloys. We attribute this finding to dynamic recrystallization, dispersion strengthening, and work hardening during hot extrusion. [Copyright &y& Elsevier]

Abstract: The effect of yttrium and erbium on the microstructure and mechanical property of Ti–16Al–27Nb alloy was investigated in this paper. Experimental results showed that the phase constituent had not been changed by Y or Er additive and all the alloys were simply composed of β, O and α phases. However, the grain size of the alloy can be sharply refined by Y or Er element. Compression test showed that the mechanical property of the alloy cannot be obviously increased by Y additive but can be sharply improved by Er additive because of the presence of fine (AlTiNb)2Er3 precipitates in the β phase. [Copyright &y& Elsevier]

Abstract: This paper deals with the effects of vacuum non-consumable arc-melting (VCAM), vacuum induction melting (VIM) and induction skull melting (ISM) technologies on microstructures, mechanical properties and oxidation resistance of Nb–16Si–22Ti–2Al–2Hf–17Cr alloy. It is revealed that the microstructure of the Nb–16Si–22Ti–2Al–2Hf–17Cr alloy is composed of Nb solid solution (Nb,Ti)ss, silicide (Nb,Ti)5Si3 and Laves phase NbCr2. The ISM ingots exhibit the finest microstructure, while the VCAM ingot shows the coarsest microstructure. Refined at 1800°C for 10min, the VIM ingot with a 0.1% carbon addition shows the best room temperature toughness of 9.05MPam1/2 on average, however, the highest strength at 1250°C was obtained on the ISM sample refined at technology parameters of 140kw melting for 2min+160kw melting for 3min. In addition, oxidation resistance was greatly improved through the ISM technology compared with the VCAM technology. [ABSTRACT FROM AUTHOR]

Abstract: A kind of graphite particle (GP) with a novel “puffed” structure and combined with the presence of oxygen-containing functional groups, were developed in our lab. In this paper, the structure and properties of the “puffed” GPs are analyzed, and the reinforcing effects of the GPs on the mechanical properties of an epoxy resin are investigated. Nanoindentation tests showed that the elastic modulus and hardness of the GPs were reduced as compared to the graphite flakes. The effects of the GPs on the properties of the epoxy with 0.5–5.0wt% of the GPs were investigated by three-point-bending test, fracture toughness and dynamic mechanical analysis. Microstructure of the GPs and fracture surfaces of the composites were examined by microscopy techniques. Results showed that flexural modulus, flexural strength and fracture toughness of the epoxy system with 5wt% GPs were increased by 13%, 43%, and 28%, respectively, over the pure epoxy. Composite specimens with 5wt% GPs also showed an apparent increase in storage modulus with respect to that of pure epoxy from DMA. Both linear elastic fracture mechanics and non-linear fracture mechanics were applied to analyze the results. [Copyright &y& Elsevier]

Abstract: In this paper, dissimilar metals welding for butting magnesium alloys AZ31, AM60 and ZK60 was conducted by a 3kW CO2 laser beam. The microstructure and mechanical properties of joints were analyzed by optical microscope (OM), energy dispersive spectrometer (EDS), scanning electron microscope (SEM), tensile machine and hardness machine. The experimental results show that the welding heat input and the chemical composition of base metal have great influences on the formation of weld bead. The results of tensile test show that the ultimate tensile strength (UTS) of the optimum joints for dissimilar metals welding is above 90% of the base metals and even higher than one of the base metals. Many precipitates distributed in the fusion zone, whose number is related to the alloy elements. The hardness test indicates that a sudden decrease of microhardness occurs in HAZ for sides of all the metals, and the hardness in the fusion zone of AZ31–AM60 joint is slightly higher than the others. The elements analysis reveals that there is an obvious compositional gradient only in the fusion zone of AM60–ZK60 joints. [Copyright &y& Elsevier]

Abstract: The B4C/BN ceramics composites were fabricated by the hot-pressing process. In this paper, the mechanical property and R-curves behavior of the B4C/BN composites were investigated. The fracture strength and fracture toughness of the B4C/BN microcomposites and the B4C/BN nanocomposites decreased gradually with the increasing content of h-BN. The fracture strength and fracture toughness of the B4C/BN nanocomposites were significantly improved in comparison with the B4C/BN microcomposites. The damage resistance and R-curves behavior of the B4C monolith and the B4C/BN composites were evaluated by the indentation-strength in bending technique (ISB). The fracture strength of the B4C monolith, the B4C/BN microcomposites and the B4C/BN nanocomposites decreased gradually with the increase of the indentation load. The B4C/BN nanocomposites retained relative higher fracture strength in comparison with the B4C monolith and the B4C/BN microcomposites under the equivalent indentation load. The B4C monolith, the B4C/BN microcomposites and the B4C/BN nanocomposites all exhibited the rising R-curves behavior. The B4C/BN nanocomposites exhibited the higher rising R-curve behavior than that of the B4C monolith and the B4C/BN microcomposites. The toughness mechanisms of the composites were investigated. The B4C/BN composites with the h-BN content more than 20wt.% exhibited excellent machinability. The slowly rising R-curves behavior remarkably improved the machinability of the composites. [Copyright &y& Elsevier]

Abstract: Microstructure and mechanical properties of Mg–4.5Al–1.0Zn (designated as AZ41M in short) alloy sheets produced by twin roll casting, sequential warm rolling and post annealing at 350°C were studied in this paper. Microstructure of twin roll casting strip consisted of dendrite structure, eutectics and intermetallic compounds located in the interdendritic region. AZ41M alloy sheets showed higher strength and lower elongation after sequential warm rolling, while post annealing after warm rolling induced the decrease of strength and increase of elongation. This results in the balance of strength and elongation in AZ41M alloy sheets. The grain refinement during manufacturing processes was attributed to the formation of heavy shear bands, high dislocation density, twinning, and precipitates of Al2Ca/Mg2Ca or Al8Mn5 and the Ca dissolution into Mg17Al12 phase. [Copyright &y& Elsevier]

Abstract: Due to the rapidly growing market for magnesium diecastings in the automotive industry in the past decade, there is a steady increase in magnesium scrap sourced from both end-of-life vehicles (old scrap) and the manufacturing processes (new scrap). In addition, the energy required to recycle magnesium is only 5% of that for extraction of primary magnesium from Mg-containing minerals. This makes magnesium recycling extremely beneficial for cost reduction, preservation of natural resources and protection of the environment. In this paper, a physical approach is presented to magnesium recycling using the rheo-diecasting (RDC) process. The RDC process was applied to process AZ91D alloy sourced from both primary alloy ingots and diecast scrap. The experimental results showed that the RDC process could be used to produce recycled AZ91D alloy with fine and uniform microstructure and very low level of porosity. The intermetallic compounds containing the impurity elements were fine and spherical particles distributed uniformly in the alloy matrix. No oxide particle clusters and oxide films were found in the RDC microstructure. The tensile properties of the recycled AZ91D alloy were comparable to those produced from the primary alloy ingots. [Copyright &y& Elsevier]

Abstract: The effect of non-woven nanofibrous membranes as interlaminar interfaces on the mechanical performance of laminated composites was investigated experimentally. The nanofibrous membranes are porous, thin and lightweight, and exhibit toughness and strength to some extent. They give little increase in weight and thickness when incorporated into a laminate. More important, they can be used as a functional agent carrier for the laminate. The nanofiber membranes used in this paper were prepared by electrospinning of Nylon-6 (PA6), Epoxy 609 (EPO 1691-410) and thermoplastic polyurethane (TPU), with a thickness ranging from 20 to 150μm. The non-woven fabrics were attached to one side of a glass/epoxy fabric lamina prior to lamination and each fabric was arranged in between two adjacent plies of the laminate. The nanofibrous membranes were characterized through scanning electron microscopy (SEM) and tensile testing, whereas the mechanical properties of the laminate were understood in terms of three-point bending and short-beam shear tests. Results have shown that the nanofibrous membranes in the ply interfaces with a proper thickness did not affect the mechanical performance of the composite laminates significantly. [Copyright &y& Elsevier]

Abstract: Porous NiTi shape memory alloys have recently attracted extensive interests for their potential use as biomedical materials. Stress–strain behaviors of porous NiTi alloy fabricated by element powder sintering in argon atmosphere were investigated in this paper by compression and flexural tests. The results indicated that the ultimate compressive strength and the flexural strength of the porous NiTi alloy depended on the densities of the porous NiTi alloy and the sintering conditions. In compression experiments, the pre-strain could completely recover while it was less than 2%. The shape recovery of porous NiTi alloy rested with the unique SME of NiTi phase and pores structure. The pores have adverse effects on the shape recovery of NiTi alloy under the experiment conditions. [Copyright &y& Elsevier]

Abstract: Life assessment for hydrocarbon processing plant components is important for both service life extension and also to minimize the potential for premature catastrophic failure. In this paper, the degradation of 2.25Cr–1Mo pressure vessel steel in a hot-wall hydrofining reactor is investigated. A test block containing a weld is exposed to the chemical service environment present within a reactor. After removal from the reactor, chemical composition, tensile behavior, impact performance are quantified and the microstructure characterized using scanning electron microscopy (SEM). Results from the tensile tests indicate that the irradiated weld and base material had similar stress–strain response. Results from the Charpy V-Notch (CVN) impact tests demonstrated that the toughness of both the base material and weld were degraded with the degradation and embrittlement of the weld zone being significantly higher than the base material. Through careful processing of additional samples extracted from the test block, using (a) de-hydrogen treatment to remove the hydrogen, (b) hydrogen charging to enrich the hydrogen content to saturated condition and (c) de-brittleness treatment, additional fracture experiments confirmed that the toughness degradation was mainly caused by high temperature tempering and not by the effects of hydrogen embrittlement due to long-term exposure. [Copyright &y& Elsevier]

The analysis of three-dimensional (3D) braided composites is more difficult due to its complex microstructure. A new type of finite element method (FEM) is developed to predict the local stress and strength within 3D braided composites under the three-dimensional mechanical loading. To verify the present method, the material properties predicted in this paper are compared with the previous work. By using the model, the stress components within a unit cell are obtained and used to analyze the strength of 3D braided composites. [Copyright &y& Elsevier]

This paper deals with the synthesis, microstructures and properties of γ-aluminum oxynitride (AlON). The thermodynamic properties of AlON were analyzed and the Gibbs energy of AlON with different compositions and temperatures were evaluated. Based on thermodynamic studies, AlON has been synthesized. The microstructures, mechanical properties and oxidation resistance of the synthetic AlON have been examined and discussed. [Copyright &y& Elsevier]

W alloys prepared via oxide dispersion strengthening have shown enhanced mechanical performance. In this paper, W-1.10 vol% Zr-2.00 vol% Y 2 O 3 (WZY) and W-1.10 vol% Zr-2.00 vol% Er 2 O 3 (WZE) were fabricated to investigate the effects of formation of complex oxide dispersions on mechanical properties and microstructure of multi-doped W alloys. By controlling the atomic ratio of added ZrH 2 and rare earth oxides through composition design, the goal of complete formation of complex oxide particles with pyrochlore structure (A 2 B 2 O 7) was achieved. Electron probe microanalysis (EPMA) and transmission electron microscopy (TEM) results showed that these dispersion particles in WZY and WZE were Y 2 Zr 2 O 7 and Er 2 Zr 2 O 7 , respectively. Moreover, microstructure analysis showed that Er 2 Zr 2 O 7 exhibited smaller size, higher number density and more homogenous distribution compared to Y 2 Zr 2 O 7 , which led to finer grains of WZE (0.58±0.03 μm) compared to WZY (1.34±0.29 μm). Finer microstructure including smaller grains and dispersion particles of WZE contributed to its higher strength and better ductility. Furthermore, the formation mechanism of complex oxide dispersion particles was discussed in detail. • W–Zr–Er 2 O 3 (WZE) and W–Zr–Y 2 O 3 (WZY) were fabricated to investigate the effects of formation of complex oxide dispersions on W alloys. • By controlling the atomic ratio of Zr:Y/Er to be 1:1, the complete formation of complex oxide particles with pyrochlore structure A 2 B 2 O 7 were achieved. • The formation of Er 2 Zr 2 O 7 and Y 2 Zr 2 O 7 can be explained by the mechanism of dissolution-reprecipitation. • Finer Er 2 Zr 2 O 7 (44.37 nm) with a higher number density distributed more homogeneously in WZE compared to Y 2 Zr 2 O 7 (92.65 nm), which made WZE have higher bending strength and better ductility performance compared to WZY. [ABSTRACT FROM AUTHOR]

This paper discusses how the accumulative alternating back extrusion (AABE) process was improved by the addition of water-quench and preheating steps to mitigate the of temperature-drop problem caused by long process flows and the problem of die gap feeding. The effect of the number of extrusion cycles on grain refinement was further investigated to elucidate and rationalize the preferred orientation in AABE. Compression experiments were carried out in tandem to explore the effect of AABE on the mechanical properties of the materials. After eight cycles of AABE, the average grain size reached 5.58 μm, and the fine-grain size reached <1 μm. Microstructure results showed that the grain size was significantly refined via discontinuous dynamic recrystallization (DDRX) and uniformity increased with subsequent extrusion cycles. Analysis of the deformation behavior of AABE showed that there was a preferred orientation in the microstructure after alternating, and the orientation of the basal plane was related to the flow velocity field that was simulated by the finite element method. A high Schmid factor and high deformation uniformity was observed after alternating, which was favorable for subsequent processing. Increasing the number of extrusion cycles decreased the material strength and plasticity up to a certain point. Subsequently, an increase was observed, with eight cycles giving the most strength and plasticity. Moreover, the grain size and crystal orientation affected the mechanical properties of the structure. These results provide an important experimental basis for creating AABE methods and fine-tuning the microstructure properties in magnesium alloy. • The grains can be refined effectively by AABE. • The material after AABE forms the (0001) basal fiber texture parallel to the velocity direction. • The higher Schmid factor reduces the deformation resistance in three main directions. • The grain refinement and the orientation segregation improve the plasticity of the material together. [ABSTRACT FROM AUTHOR]

The precipitation evolution and mechanical properties of Fe–3Si–2Cu (in wt.%) silicon steel were investigated. It is interesting to found that the precipitation of ε-Cu increases the yield strength, tensile strength and elongation simultaneously. The reconciliation of strength and toughness comes from two reasons. і) The disordered interface between ε-Cu and matrix significantly hinders dislocations. ii) The essential softness of ε-Cu with narrow strips enhances the toughness. Thus, this paper is of great significance to the mechanism of strengthening and toughening by nano-sized ε-Cu. Image 1 • The ε- Cu shows much more excellent strengthening and toughening effect than the Cu-rich cluster. • The strengthening is mainly owing to the formation of GND-modified disordered interfaces between ε-Cu and matrix. • The improvement of toughness is attributed to the essential softness of ε-Cu and the internal narrow strips. [ABSTRACT FROM AUTHOR]

This paper investigates the novel gradient temperature rolling process for ultra-heavy plates. Between rolling passes, water cooling is used to create a temperature gradient along the thickness direction of the ultra-heavy plate, which increases deformation of the core and improves the final mechanical properties of the plate. The DEFORM-3D software package was used to simulate the temperature and strain fields of the gradient temperature rolled plate. Simulation results show an obvious temperature gradient along the thickness direction of the plate and during rolling, deformation is more likely to penetrate the core. The surface to core strain ratio decreased from 14.7:1 to 1.8:1 compared to conventional rolling. Furthermore, the results of hot rolling experiments clearly show refinement of the microstructure. A layer of fine grains with an average diameter of about 1–2 μm formed on the surface of the plate and the average grain size was found to be 6.7% finer at 1/4-thickness and 11.8% finer at 1/2-thickness compared to conventionally rolled sheets. Moreover, the high-angle grain boundaries were 8.7% larger at 1/2-thickness. The microstructure of the gradient temperature rolled plate is mainly ferrite and pearlite with a small amount of granular bainite at the core. The pearlite phase initially exhibits a lamellar structure that is eventually transformed into degraded pearlite. The granular bainite is finer and more uniformly distributed compared to that of a conventional rolling plate. In addition, the yield strength and tensile strength of the gradient temperature rolling plate are higher and less elongation is observed, and the impact energy at low temperatures (−20 °C and −40 °C) is higher; from the surface to the core as the thickness increases, the decrease in impact energy is even smaller. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) was used to fabricate copper samples under various processing parameters. The influence of laser linear energy density on the microstructures and mechanical properties of the SLM copper samples were investigated theoretically and experimentally. Based on the results, the optimal linear energy density that can result in the best relative density (99.10 ± 0.5%) and surface roughness (Ra = 12.72 ± 4.54 μm) was determined to be 0.50 J/mm which corresponds to the laser power and scanning speed of 200 W and 400 mm/s, 300 W and 600 mm/s, respectively. Under the optimal processing conditions, the microhardness and strength (i.e., yield strength and ultimate tensile strength) of the copper sample achieved the highest value. In addition, it is also found that the microstructure of the SLM pure copper samples was characterized by polycrystalline grains with columnar dendrites and equiaxed structures dispersed inside. The grain size showed a decreasing trend as linear energy density increased due to the improved intrinsic heat treatment effect. The paper proves that nearly full dense copper with desirable mechanical properties can be fabricated through SLM. • A theoretical model is proposed to estimate the minimal energy density for SLM. • SLM copper fabricated under optimal laser energy density achieves a density of 99.10 ± 0.5%. • SLM copper made under optimal energy density achieves a surface roughness of 12.72 ± 4.54 μm. • SLM copper achieves comparable mechanical properties to its wrought counterpart. [ABSTRACT FROM AUTHOR]

Hot form Quench (HFQ®) represents a leading-edge hot sheet stamping technology for manufacturing complex-shaped high strength aluminium alloy panel components. Transfer of sheet blank from the furnace to the press is the first crucial step in the process. This paper reports work in which the effects of the blank transfer on the deformation of material during pressing and on the final properties after ageing through thermal-mechanical testing and microstructural observations. Two aluminium alloys are investigated, 6082 and 7075. Hardness, quasi-static uniaxial tensile measurements and TEM microstructure observations provide evidence that post-treatment properties and the underlying microstructure are strongly influenced by the blank transfer step. Severe deterioration in the post-treatment strength was observed for blank transfer temperature, ranging from 250 °C to 400 °C. The temperature-time-property (TTP) diagrams showed that 350 °C was the most sensitive temperature that reduced the post-treatment strength by 45% within 10 s holding. As evidenced by TEM, typical coarse η and S precipitates at high temperatures were identified, which resulted in different post-treatment properties and hot deformation behavior. Finally, the results from HFQ® technology processed aluminium alloys 7075 and 6082 were compared with conventional TTP diagrams, enabling comparison with conventional scientific understanding of quenching effects. [ABSTRACT FROM AUTHOR]