Search

Highlights: [•] Microstructure and properties of the HAZ were analyzed. [•] Delta ferrite morphology changed, and ferrite content decreased. [•] Adverse effect on yield and ultimate tensile strength was negligible. [•] The absorbed energy and hardness decreases with increasing number of weld-repair. [•] The sensitivity to pitting corrosion was increased. [Copyright &y& Elsevier]

Highlights: [•] As the amount of SiC particles increase, the composite’s densification declines. [•] Increasing the amount and reducing the size of SiC lead to reduced thermal conductivity. [•] The SiC particles size decreases, the grain size and the distribution of reinforcement decreases. [•] Increasing the amount and reducing the size of SiC promote high hardness in the composite. [•] The finer particle size and increasing the amount of SiC presents greater compressive strength. [Copyright &y& Elsevier]

Highlights: [•] Deep cryogenic treatment increases the hardness and war resistance. [•] Increasing he cooling rate of quench environment, improves the hardness and wear resistance. [•] Increasing the β precipitates, improve the hardness and wear behavior. [•] Predominate wear mechanism is abrasive. [Copyright &y& Elsevier]

Abstract: Development of amorphous alloy/glassy particle reinforced light metal composites is an emerging research field. In this investigation, we have synthesized and characterized Ni60Nb40 amorphous alloy particle reinforced Mg-composites with varying volume fractions. Microwave-assisted two-directional rapid sintering technique followed by hot extrusion was used to produce these pure Mg-based composites. The structural and mechanical properties of the developed composites were investigated, and are discussed using structure–property relationship. Structural analysis indicated the retention of amorphous structure of the reinforcement in all the composites. It was found that the distribution of the reinforcement was strongly dependent on the volume fraction (Vf ). The addition of Ni60Nb40 amorphous alloy particles modified the preferred crystal orientation of Mg, as was observed from X-ray diffraction (XRD) analysis. The composites showed significant improvement in hardness (increment up to 120%) and compressive strength (∼85% increase at 5% Vf ). Comparison of mechanical properties of the developed composites with those of conventional Mg-composites having ceramic/metallic reinforcements, highlight the effectiveness of using amorphous particles as promising reinforcement materials. [Copyright &y& Elsevier]

Highlights: [•] SHS was successfully applied for TiB2–Cu composites with 5–50vol.% of Cu dilution. [•] Cu as an matrix phase was formed in whole range of investigated compositions. [•] TiB2 volume fraction significantly affected the hardness (6–18GPa). [•] TiB2:Cu ratio influenced the grain size (0.6–6.4μm in size) and microstructure. [•] Cermets with the highest TiB2 content could be competitive to WC–Co cermets. [ABSTRACT FROM AUTHOR]

Highlights: [•] In this research, kinetics of borided Nickel 201 alloy was studied. [•] It was observed that the hardness of borides formed surface of steels is over 1700HV0.05. [•] The thickness of the boride layer Nickel 201 alloys is approximately 220μm. [ABSTRACT FROM AUTHOR]

Highlights: [•] A reliability value can be determined from the distribution graphics of mechanical properties. [•] The percentage of damaged parts at a value of mechanical property can be determined from graphics. [•] Mechanical property values with 10%, 50% and 90% reliability were increased with sintering time. [•] MicroVickers hardness values were not increased in generally with induction sintering time. [•] It was concluded that MicroVickers hardness is not appropriate for powder metal materials. [ABSTRACT FROM AUTHOR]

Highlights: [•] The Y addition restrains the formation of lamellar AlLi and spheroidizes the α-Mg. [•] During the solid solution at 340°C, MgLi2Al is dissolved, and AlLi precipitates. [•] During the solid solution at 440°C, AlLi is dissolved and MgLi2Al precipitates. [•] The Y addition improves the hardness and makes the hardness become stable. [ABSTRACT FROM AUTHOR]

Highlights: [•] Methods were proposed to clearly reveal microstructure constituents in Inconel-718. [•] In an as-forged Inconel-718 disk microstructure from center to edge was nonuniform. [•] Microstructure nonuniformities persisted after applying the common heat treatment. [•] So, for both conditions variation in hardness from center to edge of disk was seen. [•] The applied heat treatment was not effective in attaining the required hardness. [ABSTRACT FROM AUTHOR]

Highlights: [•] Formability of laser welded blanks was studied by limiting dome height test. [•] Dual-phase and high strength low alloy steel was used to prepare the welded blanks. [•] Effects of weld line position and geometry on formability of the welds was studied. [•] Failure location and formability were correlated to the hardness across the welds. [•] Softening was observed to affect formability in dual-phase steel welded blanks. [ABSTRACT FROM AUTHOR]

Highlights: [•] Hardness is independent of general stresses at dominating plasticity. [•] Elastic deformations introduce a stress dependence of hardness. [•] Equi-biaxial tensile stresses increase stress dependence. [ABSTRACT FROM AUTHOR]

Highlights: [•] Effect of multiple repairs on residual stress, microstructure and hardness for a clad plate has been studied. [•] A diffusion layer with martensite is generated around weld-base metal interface. [•] Along the weld–clad metal interface, short ferrite is generated in the fusion zone. [•] As the repair times increase, the content of short ferrite is increased. [•] It is proposed that the stainless steel clad plate cannot be repaired more than 2 times. [ABSTRACT FROM AUTHOR]

Highlights: [•] Development of shear testing procedures. [•] Characterisation of local strength and plastic behaviour of welds. [•] Assessment of local strain fields by digital image correlation. [•] Comparison of shear, tensile and hardness characterisation results. [ABSTRACT FROM AUTHOR]

Highlights: [•] Effect of welding velocity and pulse frequency in GMAW of HSLA steel. [•] Dependency of weldment microstructure on the welding velocity and pulse. [•] Reduction of hardness in the weld zone and HAZ with increasing of heat input. [•] The higher strength due to the higher amount of martensite. [•] Deterioration of impact properties with formation of grain boundary ferrite. [ABSTRACT FROM AUTHOR]

Highlights: [•] Mg effects on microstructure and mechanical properties of Al–Si–Mg were studied. [•] Three alloys with different amounts were cast, homogenized and exposed to T6. [•] Intermetallic compounds were formed on the microstructure by increasing Mg amount. [•] Hardness and tensile strength increased with increasing Mg content. [•] Elongation and density decreased with increasing Mg content. [ABSTRACT FROM AUTHOR]

Highlights: [•] Effect of ESR process on microstructure of Cu–Cr–Zr alloy was investigated. [•] The hardness, strength and electrical conductivity are sensitive to thermomechanical treatment. [•] The microstructure of the alloy can be optimized for obtaining the best combination of mechanical and electrical properties. [ABSTRACT FROM AUTHOR]

Highlights: [•] Production of MMC reinforced with in situ boride particles have been investigated. [•] Higher reinforcement percentage of borides was produced by a filtration technique. [•] Hardness of boride particles was measured as approximately 3050Hv. [•] The cumulative weight loss of the composite was lower than of the matrix alone. [ABSTRACT FROM AUTHOR]

Highlights: [•] We develop an ANN model for hardness drop prediction. [•] Investigating the effects of tempering conditions on hardness drop value. [•] With increasing tempering time, the hardness drop does not always increases. [ABSTRACT FROM AUTHOR]

Highlights: [•] Si partially occupies Cr site in Laves phase NbCr2 and partially forms Nb5Si3 phase. [•] The addition of Si can harden and toughen as-HPed NbCr2 alloys. [•] Fracture toughness of NbCr2–5wt.% Si is 4 times higher than cast NbCr2 alloys. [•] The toughening mechanism of Si on as-HPed NbCr2 alloys is firstly investigated. [•] Silicon can enhance the oxidation resistance of NbCr2 alloys at 1373K and 1473K. [ABSTRACT FROM AUTHOR]

Highlights: [•] Friction stir processing does not alter hardness and mechanical strength of MIG welds. [•] Friction stir processing improves fatigue life of reinforced and non-reinforced MIG welds. [•] Friction stir processing removes previous defects, such as porosity and lack of wetting. [ABSTRACT FROM AUTHOR]

Highlights: [•] Deposition of new kind of multilayer coatings TiN/a-C:H for tribological applications. [•] Analysis of hardness and elasticity modulus based on nanoindentation results. [•] Effect of bilayer period and TiN to a-C:H layers thickness ratio on mechanical properties. [•] Analysis of fracture toughness and wear mechanisms. [•] Discussion on optimization coatings architecture to obtain an excellent mechanical and tribological properties. [ABSTRACT FROM AUTHOR]

Highlights: [•] Addition of Fe and Cu improved the wear resistance and hardness of Al–28Si alloy. [•] Spray forming and hot pressing have refined the microstructures of Al–28Si alloys. [•] The wear resistance is high for spray formed and hot pressed Al–28Si–5Cu–4Fe alloy. [•] The wear resistance and the hardness are low for as-cast Al–28Si alloy. [ABSTRACT FROM AUTHOR]

Highlights: [•] Hardness of surface hybrid composite was increased. [•] Wear rate is immensely decreased at optimum condition. [•] Size of reinforcements was reduced to 5μm after Friction stir processing. [•] Good bonding between the SiC reinforcement particles and Al matrix is observed. [•] Micro voids are observed between the Al2O3 reinforcement particles and Al matrix. [ABSTRACT FROM AUTHOR]

Highlights: [•] Non-equilibrium microstructures of an Al–1Fe–1Ni alloy have been characterized. [•] Al9FeNi with an aligned rod-like morphology is the prevalent intermetallics. [•] A Hall–Petch type equation is proposed relating hardness to the cell spacing. [•] Correlation microstructure-hardness for Al1Fe, Al1Ni and Al1Fe1Ni alloys is carried out. [ABSTRACT FROM AUTHOR]

Highlights: [•] When the number of ARBF cycle increased, the grains became equiaxed. [•] The final grain size of aluminum and copper was about 200 and 50nm, respectively. [•] With increasing the number of cycles, the hardness increased. [•] The increase rate of hardness for the copper is higher than the aluminum layer. [ABSTRACT FROM AUTHOR]

Highlights: [•] T-lap and T-butt joints were fabricated by friction stir welding. [•] Original joint line with severe deformation (OJLwSD) in T-joints was studied. [•] Hardness and microstructures in different zones of T-joints were investigated. [•] Distribution and statistic data length of OJLwSD were analyzed. [•] Relationships of welding parameters, OJLwSD and properties were studied. [ABSTRACT FROM AUTHOR]

Highlights: [•] A sound FSW joint of rolled SiCp/AA2009-T351 sheet was achieved. [•] Precipitation sequences of phases varied in different regions of the joint. [•] Coarsening of precipitates and reduction of dislocation density occurred in HAZ. [•] HAZ had the lowest hardness and strength with the fracture occurring in this zone. [•] The FSW joint exhibited a good combination of strength and ductility. [ABSTRACT FROM AUTHOR]

Highlights: [•] The surface hardness is increased about eight times. [•] Increasing nitriding time and temperature caused strengthening the Al diffused zone. [•] The inward diffusion of nitrogen and outward diffusion of iron changed aluminized zone microstructure. [•] Surface aluminum oxides are reduced by plasma nitriding in low pressure chamber with nitrogen and hydrogen in gas mixture. [ABSTRACT FROM AUTHOR]

Highlights: [•] Characteristics of GP zones formed in Al–Zn–Mg cast alloys using SAXS technique. [•] GP zones formation and growth are accompanied with increase in electrical resistance. [•] Direct quenching–aging process results in significant increase in electrical resistance peak. [•] The electrical resistance peak of Al–Zn alloys was low compared to Mg-containing alloys. [ABSTRACT FROM AUTHOR]

Highlights: [•] This work investigates the effect of (0.05–0.1wt.%) Ni additions on the SAC (0507) solder. [•] Enhanced strength of SAC (0507)–0.05Ni was due to microstructural refinement and uniform distribution of the IMCs. [•] Improved ductility and worsen mechanical properties of SAC (0507)–0.1Ni alloy were due to the presence of large β-Sn grains. [•] Both YS and UTS increased with and decreasing temperature and decreasing strain rate. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this work is to investigate the effect of heat treatment on swelling, hardness and surface quality of samples from four species, namely mindi (Melia azedarch L.), mahogany (Swietenia macrophyla), red oak (Quercus falcate Michx.) and Southern pine (Pinus taeda L.). Specimens were exposed to temperature levels of 130°C and 200°C for 2 and 8h. Swelling values of the control and heat treated samples were evaluated by soaking them in water for 2h. Surface quality and hardness of the species were also determined using a stylus technique and Janka hardness, respectively. Based on the findings in this study dimensional stability of all four types of samples improved with heat treatment. Surface quality of the specimens was also significantly enhanced by exposing them to heat. Micrographs taken from scanning electron microscope revealed that there was some distortion and modification of the cells due to heat treatment. Overall hardness of the samples was adversely influenced by heat treatment. It seems that properties of the species evaluated in this investigation were more pronounced with increasing temperature and time span. [Copyright &y& Elsevier]

Abstract: Scratch testing is studied aiming at correlation of global quantities in the context of a representative stress description. Previous investigations concerning this matter have shown that good accuracy predictions for different material classes, within the framework of classical Mises elastoplasticity, can be achieved by using a combination of stresses at different levels of plastic strains to define representative quantities at scratching. It is important to emphasize though that the correlation must account for the difference in mechanical behavior at elastoplastic and rigid plastic scratching and that pertinent results have only been presented for the normal scratch hardness. It is therefore the aim presently to investigate if such a correlation can be extended to apply also for global scratch quantities in general. From a practical point of view the results are valuable both when describing the mechanical behavior at scratching and at material characterization. Predictions based on the present study can within the framework of classical Mises elastoplasticity and quasi-static conditions, be made for a wide range of materials ranging from polymers and ceramics to metals. [Copyright &y& Elsevier]

To promote the formation and growth of nitride layer, a befitting surface nano-crystallization process was introduced as a pre-treatment of nitriding, and an optimized nitriding temperature was investigated. A modification layer with a depth of 350μm was formed by ultrasonic cold forging technology (UCFT) on AISI D2 surface. A series of plasma nitriding experiments for both treated and untreated samples were conducted at various temperatures ranging from 350°C to 550°C for 4h. The influences of nitriding temperature on the hardness, microstructure, morphology and composition of the sample surface were investigated by micro-hardness tester, optical microscope (OM), 3D profile-meter and scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The diffusion of nitrogen and the formation of nitrides were markedly improved by UCFT pre-treatment. A thicker and harder nitrided layer was formed at a high nitriding temperature. However, as the nitriding temperature increased to 550°C, a stronger sputter occurred on the sample surface. The results presents that it is an optimized process to be pre-treated by UCFT and nitriding at 520°C for 4h. [ABSTRACT FROM AUTHOR]

Abstract: In the paper, the effects of processing parameters (rotational speed and duration time) on microstructure, mechanical properties of 6061-T4 aluminum alloy friction stir spot welds were investigated. Experimental results indicate that the microstructure and mechanical properties varied significantly depending on processing parameters, which significantly affect the hook geometry and material flow which in turn affected the size of stir zone. The hardness profile of the weld exhibited a W-shaped or an upside down V-shaped appearance and the minimum hardness was obtained in the periphery of the thermo-mechanically affected zone (TMAZ) and heat affected zone (HAZ). The tensile/shear strength increased with increasing tool rotational speed and duration time, in which, the rotational speed played a crucial role in determining the strength. The cross-tension strength increased dramatically with increasing duration time at the highest rotational speed. There was a direct correlation between the effective weld width and the strength, the presence of larger effective weld width resulted in stronger weld. Two failure modes were observed: shear fracture of the nugget under tensile/shear loading, and nugget debonding under cross-tension loading, the fracture path was associated to the hook geometry. [Copyright &y& Elsevier]

Abstract: The gradient mechanical properties were obtained in the electropulsing-tempered saw blade made by the high carbon steel. The tooth has a high hardness, whereas at the back the hardness is low. Owing to the high temperature induced by the electropulsing, a plastic area formed at the tooth root. In addition, the thermal compressive stress and the strong electroplasticity effect at the tooth root helped heal the cracks there effectively. Therefore, the strength and toughness of the saw blade were improved obviously, making it meet the high requirements for the cutting performance. The results are attributed to the detour effect of the pulse current during the electropulsing–tempering treatment. [Copyright &y& Elsevier]

[Display omitted] • (Al,Mo,Ta,V,W)N 0.79 and -N 0.33 show columnar microstructures. • The oxynitride features a renucleated finer, randomly oriented microstructure. • N-deficiency of (Al,Mo,Ta,V,W)N is beneficial for hardness and phase stability. • The oxynitride is harder than the N-rich nitride in as-deposited state. • The oxynitride cracks open during annealing due to formation of binary oxides. (Al,Mo,Ta,V,W)-N 0.79 , -N 0.33 , and -N 0.88 O 0.12 coatings were sputtered in N 2 -rich, N 2 -lean, and N 2 +O 2 containing atmospheres. The face-centered cubic structured coatings feature as-deposited hardness values of 32.3, 39.7, and 34.5 GPa, respectively. The (Al,Mo,Ta,V,W) N 0.79 and (Al,Mo,Ta,V,W)N 0.33 consist of highly oriented columns, plus some very large grains in the latter coating. During vacuum annealing at 800 °C for 30 h, the (Al,Mo,Ta,V,W)N 0.79 loses N down to 25 at.%, while the (Al,Mo,Ta,V,W)N 0.33 remains stable. Their alignment in chemical composition also caused an approach of their hardness values with 35.2 and 38.1 GPa, respectively. The (Al,Mo,Ta,V,W)N 0.88 O 0.12 exhibits partly tilted and randomly oriented smaller columnar grains than the nitrides, and the hardness drops from 34.5 to only 14.1GPa when vacuum annealed due to massive phase-transformations toward individual oxides and the connected crack formation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nix-Gao model combined with pileup corrections are critical to improve the accuracy of bulk equivalent hardness from nanoindentation testing. • Evaluating bulk hardness by hardness ratio or changes at a reference depth will cause quantitative errors as large as 60%. • Constant strain rate and constant loading rate tests result in comparable hardness for materials with a weak strain rate sensitivity. • The curvature in Nix-Gao fitting is not simply caused by nanoindentation testing procedures. • Size dependent dislocation obstacle strengths are essential for accurate microstructure- and nanoindentation-predicted strength change. Estimations of bulk hardness from nanoindentation are frequently subject to considerable uncertainties due to indentation size effects (ISE), pileup effects, and potential influence of surface quality or test methods. This study examined materials science principles of nanoindentation test methods to enable accurate prediction of bulk hardness for a series of high purity Fe and Fe-(3–25 wt%) Cr alloys. These materials were tested in as-annealed and thermally aged (100–900 h at 475 ℃ to produce Cr-rich α' precipitates) conditions. Nanoindentation with a Berkovich indenter at constant strain rate (0.05–0.5 /s) and constant loading rate conditions provided comparable bulk equivalent hardness (H 0) extracted by Nix-Gao model, indicating a weak strain rate sensitivity at room temperature. Results from electropolished and fine mechanically polished samples gave comparable measured hardness. Pileup corrections produced a 5–14% correction to H 0 which agreed with the experimental bulk Vickers hardness within ∼10% for most tested materials. The microstructural model-predicted and measured strength values agreed for aged samples. A derived analytic expression demonstrates that an ISE error, associated with inappropriate methods such as hardness ratios or changes at a reference depth, would be as large as 60% in estimated bulk hardness for the investigated Fe-Cr alloys. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hardness anisotropy associated with crystal orientation governs surface damage morphology in LiNbO 3. • A 20% difference in hardness can double the characteristic strength of LiNbO 3. • Tailored high Young's modulus surface planes of LiNbO 3 can significantly increase its characteristic strength. Piezoelectric single crystalline materials are paramount for high-speed data transfer in 5G technologies. The functionality of the end-devices demands temperature independent frequency filtering and high surface acoustic wave velocities, which are associated with the orientation dependent thermo-physical properties of the piezoelectric substrate material. Single crystalline Lithium Niobate (LiNbO 3), cut in particular directions, has proven to have outstanding functional properties, yet its brittle character along with the highly anisotropic mechanical properties may limit its use in demanding applications. In this study, the effect of crystal orientation on hardness and on mechanical strength is demonstrated by comparing nanoindentation results and finite element analysis supported biaxial strength experiments for two LiNbO 3 samples with different orientation. It is demonstrated that the crystal anisotropy leads to differences in hardness up to ∼ 20% between both orientations, with the characteristic strength being double in the harder direction. The observed correlation is rationalized based on the effect of surface finish and distinct sub-surface damage in the corresponding crystal orientations. Additional strength measurements on nano-scratched samples revealed a significantly higher remaining strength for the harder orientation due to less (sub-) surface damage. These findings can be exploited in future design of single crystalline substrate materials with higher reliability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Texture intensity decreased due to the uniform distribution of α phase after EST. • The average hardness of specimen decreased but the ductility was enhanced after EST. • TEM results indicated that the α phase was distributed uniformly after EST with 0.03 s. • After EST, more atom vacancies and lattice distortion were formed near α/β interfaces. • Atom vacancies and lattice distortion could reduce hardness and improve ductility. Effects of electroshock treatment (EST) on the microstructural evolution and mechanical properties of near-β titanium alloy (Ti-55531) formed by directed energy deposition (DED) was studied in this work. With the increase in EST time, the average hardness of specimen decreased from 426 HV to 316 HV, and the fracture strain increased significantly, which was attributed to the uniform dispersion of α phase along grain boundaries and inside the β grains. After EST, the texture intensity decreased in terms of the orientation distribution function (ODF), which was ascribed to the redistribution of α phase. Moreover, more atomic vacancies and lattice distortion were formed near the α/β interfaces, which were verified by transmission electron microscopy (TEM) observation and ascribed to the migration of atoms near the interface under EST. External loadings facilitated the dislocation motion and lattice distortions near the interfaces, which resulted in the reduction in hardness and the improvement in ductility. The above results indicated that EST can quickly alter the microstructure and mechanical properties of DED titanium alloys as a simple and energy-saving method. [ABSTRACT FROM AUTHOR]

[Display omitted] • High chromium white cast irons containing niobium macro-additions show great promise in abrasive wear applications. • Increasing niobium content of the alloy linearly increased the hardness of heat-treated dual-reinforced hypo-eutectic high-Cr white irons. • Clear beneficial effect of Nb macro-addition on abrasive wear behaviour was observed under both less-competent and competent abrasive rocks. • In optimum addition ranges, life improvements of 37% and 7% per 1 wt%Nb were achieved under less-competent and competent abrasives, respectively. • Resultant NbC particles mostly protruded above matrix and Cr-rich carbides in the wear scars under controlling wear mechanism of micro-fracture. Abrasive wear is a principal cost in mining and mineral processing operations. High chromium white cast iron (WCI) further reinforced with niobium carbide (NbC) shows promise to increase component wear lives. This work investigates the effect of niobium macro-additions on microstructure, hardness and high-stress abrasive wear behaviour of Nb-containing high-Cr WCIs. Eight alloys with Nb between 0 and 10.7 wt% were produced by sand casting. Increasing niobium carbide volume fraction (Nb-CVF) increased hardness from 724 to 812 HV (7.3 HV per 1% Nb-CVF). Abrasive wear resistance, assessed using the ball mill abrasion test in basalt (less competent) and quartzite (competent rock), showed clear beneficial effect of NbC macro-addition up to 11.4 and 7 vol% in basalt and quartzite, respectively. These correspond to life improvements of 37% and 7% per 1% Nb-CVF in the optimum range of Nb macro-addition, in basalt and quartzite respectively. Micro-mechanistic observations of worn surfaces showed that NbC particles not only protrude from the matrix but do so more than Cr-rich M 7 C 3 carbides. In deep wear grooves created by quartzite, M 7 C 3 particles were cut flush with the matrix, whereas NbC protruded, visibly impeding the progress of the abrasion event. [ABSTRACT FROM AUTHOR]

[Display omitted] • Anisotropic hardness evolution appears during artificial aging when changing the loading axis of samples. • Due to fiber texture and inhomogeneous distribution of T 1 (Al 2 CuLi) variants, different amounts of face-on/inclined T 1 will be encountered in different loading directions. • The face-on/inclined T 1 has a higher resistance ability to hardness loading compared to edge-on T 1. • The pre-stretching prior to aging can effectively facilitate the isotropy of hardness evolution. Anisotropy of mechanical properties has limited the further application of Al–Cu–Li alloys. Previous research efforts were mostly focused on the anisotropic tensile properties. In the present study, significant hardness anisotropy evolution, measured during artificial aging, was also established when loading in different directions. It was found that different amounts of inclined/face-on would be encountered when loading along different directions, resulting from the fiber texture and inhomogeneous distribution of T 1 (Al 2 CuLi) variants along different directions for the samples without pre-stretching. The resistance to hardness loading is different between the face-on/inclined T 1 and edge-on T 1 due to its high aspect ratio, so the measured anisotropic hardness is obtained. Moreover, the characteristics of precipitates also play an important role in the anisotropic hardness evolution, the strong anisotropy of hardness only appears in the alloys that contained large diameters and a low density of T 1 phase or θ' (Al 2 Cu) phase. After applying pre-stretching, the predominant T 1 phase precipitates with small diameters and a high density, which helps to facilitate the isotropic hardness evolution during artificial aging. These findings provide a necessary supplement for the hardness evaluation where a high aspect ratio of precipitate is involved. [ABSTRACT FROM AUTHOR]

[Display omitted] • A high-throughput experiment for steels based on LMD and GTHT was developed. A machine learning model possessing microstructure input terminals was put forward. • The average error of validation set in microhardness can be as low as 14.37 HV. • The reported strategy holds the promise for the application to other martensite steels. Accurately predicting properties of steels containing martensite by using models based on traditional strengthening mechanisms remains a challenge. In this study, a smart machine learning model possessing two-dimensional microstructure input terminals was developed using high-throughput experiments and machine learning on steels for low-temperature service. An algorithm based on a convolutional neural network enriched with the two-dimensional input terminals increased the prediction accuracy, achieving an average microhardness error of as low as 14.37 HV for the validation set. The improved prediction accuracy is ascribed to the comprehensive strengthening mechanism and coupling of strengthening effects contained in the multifarious input terminals. The information acquisition and cross-correlation of substructures related to strengthening mechanism played an important role. The reported strategy can deepen the cognition of the strengthening mechanism of tempered martensite. It is promising for application to different steels containing tempered martensite. [ABSTRACT FROM AUTHOR]

[Display omitted] • The C14 Mg 2 Ca Laves phase retains its hardness up to at least 200 °C. • Despite significant strength differences, slip transfers from α-Mg to the C36 phase. • An orientation relationship between α-Mg and C36 basal planes exists at 82 ± 10°. • Slip transfer into C36 Laves phase occurs along basal planes. • The mechanism of co-deformation and possible future work directions are explained. The microstructure of Mg-Al-Ca alloys consists of a hard intra- and intergranular eutectic Laves phase network embedded in a soft α-Mg matrix. For such heterogeneous microstructures, the mechanical response and co-deformation of both phases under external load are not yet fully understood. We therefore used nano- and microindentation in combination with electron microscopy to study the deformation behaviour of an Mg-3.68Al-3.8Ca alloy. We found that the hardness of the Mg 2 Ca phase was significantly larger than the α-Mg phase and stays constant within the measured temperature range. The strain rate sensitivity of the softer α-Mg phase and of the interfaces increased while activation volume decreased with temperature. The creep deformation of the Mg 2 Ca Laves phase was significantly lower than the α-Mg phase at 170 °C. Moreover, the deformation zone around and below microindents was dependant on the matrix orientation and was influenced by the presence of Laves phases. Most importantly, slip transfer from the α-Mg phase to the (Mg,Al) 2 Ca Laves phase occurred, carried by the basal planes. Based on the observed orientation relationship and active slip systems, a slip transfer mechanism from the soft α-Mg phase to the hard Laves phase is proposed. Further, we present implications for future alloy design strategies. [ABSTRACT FROM AUTHOR]

[Display omitted] • The as-fabricated WC-Co microstructures were characterized by two types regions. • Heat-treatment homogenizes the heterogeneous microstructure of as-fabricated WC-Co. • Co and C of heat-treated LPBF samples reduced by laser irradiation. • The C addition to the WC-17Co affected the constituent phases after heat treatment. • Co and W 3 Co 3 C phase area fractions in heat-treated samples affect Vickers hardness. In this study, an attempt is made to control the WC-Co two-phase microstructures by laser powder-bed fusion (LPBF) process using cemented carbide powders with different compositions of WC-25Co (mass%) and WC-17Co (mass%) and post heat-treatment at 1380 °C. The as-built cemented carbide samples had different microstructures from those of the cemented carbides fabricated by conventional manufacturing methods. The microstructures of the as-fabricated WC-25Co and WC-17Co cemented carbides were characterized by two types of regions. Region 1 consisted of W 2 C and W 3 Co 3 C phases, including numerous pores and defects. Region 2 consisted of WC and Co phases. Post heat-treatment of the LPBF-built WC-25Co sample at 1380 °C led to the formation of a defect-free WC-Co two-phase microstructure. In contrast, the W 3 Co 3 C phase remained in the LPBF-built WC-17Co sample even after heat treatment. The addition of carbon to the WC-17Co powder prevented the formation of the W 3 Co 3 C phase in the cemented carbide processed by LPBF and subsequent heat treatments. The addition of carbon to the WC-17Co powder had a slight effect on the hardness of as-fabricated samples, but reduced the hardness of heat-treated samples. The reduced hardness was attributed to the increased volume fractions of the WC and W 3 Co 3 C phases. [ABSTRACT FROM AUTHOR]

Abstract: The contours of equivalent plastic strain (EPS) and shear strain (SS) over the cross section of backward extruded AZ91 magnesium alloy have been modeled employing the finite element method (FEM). The results indicate that the distributions of EPS and SS are not homogenous at different regions over the products’ cross section. In addition, the microstructure evolutions and strain pattern relationship have been explored through applying the backward extrusion (BE) method in the temperature range of 250–450°C. The results indicate that the microstructural features (grain size, mechanical twins and γ-second phases) of different regions are strongly affected by applying backward extrusion, which is fairly consistent with the heterogeneous strain distribution. The obtained results are properly addressed relying on the principal deformation and restoration mechanisms, which operate under specified deformation conditions. The hardness measurements have been also employed to trace the related changes. [Copyright &y& Elsevier]

Abstract: A high strength Mg–8.0Zn–1.0Al–0.5Cu–0.5Mn(wt.%) magnesium alloy with outstanding ductility was developed using a common casting technique and heat treatment. The microstructure of the as-cast alloy is composed of α-Mg, MgZn, MgZnCu and Al–Mn phases. After the solution treatment and subsequent two-step aging treatment, the yield strength (YS), ultimate tensile strength (UTS) and elongation of the alloy at peak hardness reach 228MPa, 328MPa and 16.0% at room temperature, respectively. The comprehensive mechanical properties of the alloy are superior to almost all other high performance casting Mg alloys. [Copyright &y& Elsevier]

Abstract: In this paper, the effects of isothermal annealing on the hardness and elastic modulus of a Cu36Zr48Al8Ag8 bulk metallic glass (BMG) were investigated. It has been shown that the Vickers hardness increases from ∼481Hv (as-cast state) to ∼518Hv after annealed for 20min. Nanoindentation tests also showed that the hardness and elastic modulus increase from ∼6.45GPa and ∼113.0GPa (as-cast state) to ∼7.27GPa and ∼130.9GPa after annealed for 20min, respectively. The results indicated that the free volume of the BMG decreased and nanocrystals nucleated during annealing. The annihilation of the free volume decreased the nucleation ratio/sites of the shear bands, while the nucleation of nanocrystals inhibited the propagation of the shear bands. Both effects are responsible for the enhancement of the hardness and elastic modulus of the BMG. [Copyright &y& Elsevier]

Abstract: Considering the phase transformation and its latent heat effect, a multi-physical field coupling numerical model is built to reproduce the deep cryogenic treatment (DCT) of a newly developed cold work die steel Cr8Mo2SiV (SDC99) specimen, and to predict the microstructure and hardness distribution and the dimensional change. In addition, an experimental setup is designed to validate the cooling behavior of DCT. The results indicate that, during DCT, the differences in temperature and cooling rate between the surface and core of specimen is very significant. However, the acute temperature and cooling rate changes are mainly concentrated on the specimen surface region about 1/3 of the sample thickness, while these changes are performed in a slow and gentle manner at the core region of specimen. After DCT, the unstable retained austenite contained in quenched specimen will significantly decrease, but this phase transformation is still incomplete. Accompanied with this phase transformation, the dimensional change of specimen is inevitable. At the initial stage of DCT, the dimensional change undergoes a rapid increase. Subsequently, the dimensional change shows a very slow increase. Meanwhile, the Rockwell hardness of specimen after DCT will also increase to 65HRC. Compared with the experimental results, these predicted results present a quite good accuracy, which indicate that the multi-physical field coupling simulation is an effective method to evaluate the cooling behavior of DCT. [Copyright &y& Elsevier]

Abstract: In the present work, Al–30Mg2Si–2Cu alloy has been spray formed and subsequently hot pressed for densification. The alloy is then subjected to solutionizing and isothermal aging treatments. The microstructural features, hardness and wear behavior of spray formed and secondary processed alloys have been evaluated individually and compared with that of as-cast alloy. The microstructure of spray formed alloy showed refined and globular shaped primary Mg2Si intermetallic particles and Al2Cu precipitate particles uniformly distributed in Al matrix. The microstructure was refined further after hot consolidation. The microstructure after solution heat treatment appeared similar to that of the spray formed alloy but aging led to a further refinement in the microstructure compared to that of the hot pressed alloy. The evaluation of wear behavior of these alloys, under dry sliding condition, showed that the age hardened alloy exhibits maximum wear resistance and minimum coefficient of friction over the entire range of applied load (10–50N) at a sliding speed of 2ms−1 followed by hot pressed, spray formed and solution heat treated alloys. The as-cast alloy showed the least wear resistance and highest coefficient of friction. Similar trend has been observed even in their hardness values too. The wear resistance of the alloys is discussed in light of their microstructural modifications induced during spray forming and subsequent secondary processing and also the topography of worn surfaces. [Copyright &y& Elsevier]

Abstract: The synergesic effect from copolymerising polysiloxane and epoxy functionality offer a viable encapsulant material for use in electronic devices. A series of epoxy group-containing organopolysiloxane without ether bond spacer was prepared. The cross-link density was progressively monitored by controlling the mole ratio of the epoxy monomer. Thermal, optical, dielectric and hardness properties were measured and related to the cross-link density. The crosslink density affect an increase in refractive indices in the range 1.4359–1.4655 and dielectric constants in the range 2.78–3.34 at 500MHz. Transparency were in the range 60–80% in visible region. A higher crosslink structure displays an improved transparency in the UV–visible region. These observations were related to changes in free volume and group polarizability and discussed within the scope of Lorentz–Lorenz relationship. [Copyright &y& Elsevier]