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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: [•] 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: [•] 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: [•] 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]

[Display omitted] • Realisation of bi-metallic laminates by wire-arc additive manufacturing. • Evaluation of design strategies for sound and defect-free deposition. • Significant impact of mutual direction of deposition on shear strength. • Performance enhancement by interlocking aided metallurgical bonding. • Limited effect of intermediate machining before second material deposition. While the recent research in manufacturing bi-metallic structures using wire and arc directed energy deposition focuses on feasibility studies to understand material compatibility, the study presented here encircles a larger design framework, integrating deposition process, intermediate surface conditions, and mutual deposition (hatching) direction. The investigation addresses the issues associated with manufacturing actual bi-metallic structures and shades light on the intrinsic mechanism responsible for process-induced anisotropy and resulting interfacial strength. Interfacial shear tests of the candidate bi-metallic pair of low-carbon steel-316L stainless steel reveal that the intermediate machining before deposition of the second material, if deposited with low dilution and low heat input has a limited effect on the final build quality. The deposition direction influences the isotropy, i.e., strength improves when the shear force acts transversely to the deposition direction of the second material. Interlocking promoted by favorable deposition direction, as revealed by fractography, combined with metallurgical bonding, enhances the interfacial strength. Despite element migration and hardness spike in the interface up to 500 HV due to martensitic needles, a defect-free bi-metallic structure was possible with shear strengths over 400 MPa. The investigation contributes to the fundamental understanding of the approaches suitable for the deposition of sound bi-metallic structures. [ABSTRACT FROM AUTHOR]

[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]

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]

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: 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]

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]

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: 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: 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]

Abstract: The microstructure and properties of 17wt.% Cr–2.9wt.% C cast irons with up to 3.17wt.% Nb additions, in both as-cast and heat treated state, have been studied. Also the influence of titanium and cerium on the structure and properties of 17wt.% Cr–2.9wt.% C-2wt.% Nb alloys are examined. NbC carbides present in the structure of tested alloys, due to their characteristic morphology, show higher wear resistance and toughness than M7C3 carbides. Increasing amount of this type of carbides, caused by the increase of niobium in Fe–Cr–C–Nb alloys, contributes to the improvement of wear resistance and dynamic fracture toughness. The alloy containing approximately 3% Nb gives the best compromise between wear resistance and fracture toughness. This alloy shows about 30% greater dynamic fracture toughness and about 30% greater abrasion wear resistance than the basic Fe–Cr–C alloy. Titanium and cerium affect the crystallisation process of Fe–Cr–C–Nb alloys and the transformation of austenite during the cooling after solidification. The addition of 0.26% Ti results in a substantial change in the morphology and distribution of NbC carbides. The secondary carbides which precipitate in the matrix regions of the tested 17wt.% Cr–2.9wt.% C-2wt.% Nb white iron containing titanium has an impact on the abrasion behaviour and fracture toughness. The alloy containing 0.28% Ti and 0.19% Ce has pearlite–austenitic matrix microstructure in as-cast condition. The pearlite, due to its high microhardness, improves the wear resistance under low-stress abrasion conditions, but drastically reduces the toughness of tested alloy. [Copyright &y& Elsevier]

Abstract: The current study presents some fundamental observations on the effects of the welding heat input in the chemical composition, microstructure, hardness and petroleum corrosion resistance of the fusion zone, formed by the AWS E309MoL austenitic stainless steel covered electrode and the AISI 410S ferritic stainless steel, being a dissimilar welding procedure. Such welding configurations are widely used as an overlay of equipment in the petroleum and gas industries. The welds were performed with the application of three different levels in heat inputs (6, 9 and 12kJ/cm). Samples of the weld metals were conventionally prepared for the microstructural characterization by light microscopy and scanning electron microscopy. A corrosion test with samples immersed in heavy oil heated at 300°C, was carried out for a period of 60h. The corrosion rate was determined by the weight loss given after the aforesaid test. The fusion zone microstructure has a typical δ-ferrite acicular morphology, from which the level of δ-ferrite was duly altered with the increases of the welding heat input, due to the variations in the composition of the weld metal caused by dilution. It was also concluded that the chemical composition and the weld metal microstructure had a slight influence in the material’s corrosion rate. As a matter of fact, the corrosion rate of the weld metals evaluated herein, was considered satisfactory with few variations between the welding heat inputs duly applied. [Copyright &y& Elsevier]

Abstract: In present paper, an attempt was made to examine the effect of different concentrations of Fe (0.5, 1, 1.5, 2 and 3wt.%) on the microstructure and tensile properties of an in situ Al–15wt.%Mg2Si metal matrix composite (MMC). The composite was made by casting process and characterized by optical microscope, scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy. The results depicted that the addition of 2wt.% Fe to the MMC changes the morphology of primary Mg2Si from irregular to polyhedral shape and reduces its average particle size from 33μm to 15μm. The microstructural studies also showed that the addition of Fe leads to the formation of Fe-rich intermetallics with polyhedral, plate-like and star-like morphology. Hardness results demonstrated that Fe addition to Al–15%Mg2Si composite has a positive effect on the hardness improvement. Further investigations on tensile tests revealed optimum Fe (1wt.%) level for improving tensile properties. In the point of fracture behavior of the composite, Fe-containing specimens showed a brittle mode of failure. [Copyright &y& Elsevier]

Abstract: Starting with elemental (pre-mixed) powders for producing shaped powder metallurgy alloys provides some advantages over a pre-alloyed system. The premixed powders are softer than prealloyed powders and therefore by using premixed powders it is possible to have higher compact densities and within a longer die life. In this research work, elemental aluminum powder was mixed with copper and magnesium in various ratios. They were compacted, sintered and heat treated in order to produce light but strong Al-based powder metallurgy alloys. The main focus of this paper is on the effects of micro to macro scale addition of magnesium on the aging response of Al4Cu alloys. Four per cent Cu gives Al powder metallurgy alloy a good control of sintering and a large space for solution treatment. Minor addition of Mg with little amount of Fe, comes from the based Al and Cu powders, enhances the hardness values of Al4Cu powder metallurgy alloys. Highest hardness value was 118HB obtained from 24h aged Al4Cu2Mg alloy. [Copyright &y& Elsevier]

Abstract: In the present work, a heat treatment process was used to modify corrosion behavior of heat affected zone (HAZ) and weld metal (WM) in welded pipe steel of grade API X70. A one-step austenitizing with two-step quenching and subsequent tempering treatment was performed to alter the microstructure of HAZ and WM. The hardness and strength values were controlled to be in the standard range after the heat treatment process. In order to investigate the effect of the heat treatment on the corrosion properties of welded joint, the samples were immersed in a mixture of naturally aerated 0.5M sodium carbonate (Na2CO3) and 1M sodium bicarbonate (NaHCO3) solution with pH of 9.7 for 45days. The electrochemical impedance spectroscopy (EIS) measurements were carried out then to study the protective properties of the corrosion products layer. The X-ray diffraction (XRD) investigation depicted that the corrosion products layer composition includes FeCO3, FeO(OH), Fe3O4 and Fe2O3. The EIS results showed that, the corrosion resistance of HAZ and WM increased after heat treatment. This can be attributed to formation of uniformly distributed polygonal ferrite (PF) and to the decrease in the volume fraction of bainite (B) after heat treatment. [Copyright &y& Elsevier]

Abstract: The 6005A-T6 aluminum alloy was friction stir welded at different welding speeds. The peak temperature, microstructure and mechanical properties were examined for these joints. A special attention was devoted to the relationship between the precipitates evolution within different zones and the local hardness. In the nugget zone (NZ) experiencing the highest peak temperature, the β″ precipitates dissolved into α-Al matrix during welding, and the hardness of NZ depended on the level of natural aging (NA) at different welding speeds. The thermo-mechanically affected zone (TMAZ) is characterized by elongated grains with a high density of dislocations. The welding speed had not a significant effect on hardness in this zone. The heat-affected zone (HAZ) contains the transformation of β″–β′, the precipitation of Q′ and the coarsening of precipitates. The HAZ close to the joint center line exhibited the minimum hardness due to the coarsening of β′ and Q′ precipitates while the HAZ far from it having a high hardness level was mainly related to coherent β″ precipitates. The HAZ hardness and joint strength have an increased tendency with increasing the welding speed. It can be explained by increasing the density of Q′ or β″ precipitates. [Copyright &y& Elsevier]

Abstract: Sn–0.7wt%Cu–1.0wt%Ag and Sn–0.7wt%Cu–2.0wt%Ag alloys were directionally solidified under transient conditions undergoing cooling rates varying from 0.1 to 25K/s. The microstructure was characterized along the castings lengths and the present experimental results include the secondary dendrite arm spacing (λ 2) and its correlation with: the tip cooling rate () during solidification and microhardness (HV), yield tensile strength (σ y), ultimate tensile strength (σ u) and elongation to fracture (δ). The aim is to examine the effects of Ag content and tip cooling rate on both the microstructure and mechanical properties. The initiation of tertiary branches within the dendritic arrangement, as well as the distinct morphologies of the intermetallic compounds (IMC) related to the solidification cooling rate was also assessed for both examined alloys. While the Cu6Sn5 phase appeared as large faceted crystals along the entire casting length, very fine Ag3Sn spheroids prevailed at higher cooling rates (>7.5K/s and>4.0K/s for 1.0wt%Ag and 2.0wt%Ag alloying, respectively) with a mixture of Ag3Sn coarser spheroids and fibers predominating at lower cooling rates. The Sn–0.7wt%Cu–2.0wt%Ag alloy exhibited smaller dendritic spacings and HV of about two times higher than the corresponding values of the Sn–0.7wt%Cu–1.0wt%Ag alloy. A single Hall–Petch equation is proposed relating δ to λ 2 for both alloys, which means that the increase in Ag content from 1.0 to 2.0wt% does not affect the elongation. It is shown that δ decreases with the increase in λ 2. [Copyright &y& Elsevier]

Abstract: Reverse dual-rotation friction stir welding (RDR-FSW) has great potential to obtain appropriate welding conditions through adjusting the independently rotating tool pin and surrounding shoulder. The welding torque exerted on the workpiece by the reversely rotating shoulder also cancels off a part of the welding torque exerted by the rotating tool pin, thus the clamping requirement for the workpiece is also reduced. In the present paper, a tool system for the RDR-FSW was designed and successfully applied to weld high strength aluminum alloy 2219-T6, and then microstructures and mechanical properties of the optimized joint were investigated to demonstrate the RDR-FSW characteristics. The weld nugget zone was characterized by the homogeneity of refined grain structures, but there was a three-phase confluction on the advancing side formed by different grain structures from three different zones. The tensile strength of the optimized joint was 328MPa (73.7% of the base material), showing an obvious improvement when compared with the optimized joint welded by the FSW without the reversely rotating assisted shoulder. The tensile fracture occurred in the ductile fracture mode and the fracture path propagated in the weakest region where the Vickers hardness is the minimum. [Copyright &y& Elsevier]

Abstract: This work deals with the surface analysis, mechanical properties and wear performances of the clad layer, which is made from tungsten carbide (WC) powders on SKD61 die steel by the gas tungsten arc welding method. According to the experimental results, due to the high hardness and elastic modulus reinforcements (Fe3W3C and M7C3) existing in the WC clad layer, the WC clad specimen has excellent wear performance at different sliding speeds. According to the wear analysis, wear behaviors of the WC clad layer are two-body abrasion and oxidation wear. In addition, oxidation wear dominates the wear behaviors of the SKD61 die steel specimen at different sliding speeds. [Copyright &y& Elsevier]

Abstract: The evolution of crystallographic texture and the mechanical properties of copper subjected to severe plastic deformation (SPD) using equal channel angular pressing (ECAP) were investigated. Samples were subjected to ECAP under two different processing routes: B 60 and BC . As the cross sections of the samples were circular, a new route with a rotation angle of 60° in the same direction between consecutive passes was introduced. The material exhibited texture development similar to the simple shear texture in both routes and the most significant changes in texture strength in both processing routes took place after the second pass. Microstructure of ECAP processed samples were investigated using electron backscatter diffraction (EBSD) analysis. Comparison of the EBSD data with optical micrograph of the initial sample confirmed that ECAP process has led to a significant decrease in grain size. Significant increases in hardness and tensile strength were observed after the first pass of ECAP. Variations of tensile strength as a function of the number of passes were related to the dislocation densities and the average boundary spacing. [Copyright &y& Elsevier]

Abstract: The paper deals with the hard coating material selection using various multi-criteria decision making approaches. Large number of materials has stimulated intense research in the field of material selection. Various quantitative decision making approaches are employed to select hard coating material selection. Technique for order preference by similarity to ideal solution (TOPSIS) is used for ranking these materials. Material selection charts (Ashby approach) is used to select hard coating materials. Pareto-optimal hard coating materials are determined for trade-off between hardness (H), H/E and H 3/E 2 (E: Young’s modulus). Hierarchical clustering is used to classify hard coating materials under study. Pearson correlation coefficients are calculated between the materials properties under study which can be integrated with materials informatics for rapidly screening and designing materials. [Copyright &y& Elsevier]

Abstract: The correlation of hardness values at scratch testing is studied within the framework of a differentiated description of representative stress values. The analysis is based on hardness values determined from a comprehensive finite element study of scratching of classical elastoplastic materials using a conical indenter. Large deformations are accounted for and the strain-hardening behaviour is varied in order to achieve generality of results. It is shown that good accuracy predictions for different material classes can be achieved by using a combination of stresses at different levels of plastic strains to define representative quantities at scratching. It is also shown that this correlation must account for the difference in mechanical behaviour at elastoplastic and rigid plastic scratching. From a practical point of view the results are valuable both when describing the mechanical behaviour at scratching and at material characterization. From the generality of the analysis, both elastoplastic and rigid plastic behaviour are accounted for, predictions based on the present study can be made for scratching of highly elastic materials such as polymers and ceramics but also for scratching of metals when plasticity dominates. [Copyright &y& Elsevier]

Abstract: The objective of this study was to evaluate effect of heat treatment and compression on some properties of Eastern redcedar (Juniperus virginiana) including bonding strength, hardness and surface quality. Specimens were exposed to three temperature levels of 120°C, 160°C and 190°C for 6h before they were compressed using 2.5MPa pressure for 5min. Polyvinyl acetate (PVAc) bonded specimens showed 23.6% reduction in their shear strength when they were exposed to a temperature of 120°C. Such strength reduction values were 44.4% and 64.1% for the specimens exposed to temperature levels of 160°C and 190°C, respectively. The lowest average Janka hardness value of 214.08kg was determined for the samples exposed to a temperature of 190°C while those treated with a temperature of 120°C had the highest hardness value of 397.73kg. It appears that combination of heat treatment and compression enchanced overall surface quality of the samples in the form of their roughness determined using stylus type equipment. [Copyright &y& Elsevier]

Abstract: Normally, increase in strength and wear resistance of tool steels is associated with a reduced ductility. However, deep cryotreatment (DCT) may be used to simultaneously increase tensile strength and hardness and improve ductility of tool steels. In this work, effects of different DCT cycles on mechanical properties of 1.2542 tool steel have been studied. Three sets of specimens were investigated: two sets of untreated specimens, for studying the effect of some hardening parameters on the metal properties, and a third set consisting of cryotreated specimens. Soaking and tempering temperatures were kept constant at −196°C and 200°C, respectively. Different cryotreatment cycles were implemented by varying soaking time (24, 36 and 48h) and tempering duration (60, 120 and 180min). In order to ensure optimum treatment conditions, time gaps between various treatment steps were kept to minimum. Results show that two cryotreatment cycles consisting of: (i) 36h soaking at −196°C and 1h tempering at 200°C, and (ii) 48h soaking at −196°C and 2h tempering at 200°C produce the best effects in the cryotreated 1.2542 tool steel specimens, namely 32–36% increase in tensile strength, 9–12% increase in hardness, and 12–35% improvement in ductility. [Copyright &y& Elsevier]

Abstract: This paper examines whether the physical properties of materials can be useful predictors of psychophysical properties of materials. In this study psychophysical methods were employed to study the link between the measured surface roughness, elastic modulus and thermal effusivity and the perceptual qualities of roughness, hardness and coldness, for a diverse set of materials (woods, polymers and metals). A strong positive correlation was found between the physical and the psychophysical properties of materials that determine touch perception. Furthermore, by analysing the data in which vision of the sample was controlled, it was found that in some cases there is a shift in touch perception between the sighted and unsighted condition that affects polymer samples most strongly. [Copyright &y& Elsevier]

Abstract: In this investigation, a neural network model is developed to predict the hardness of high carbon steels. The inputs to the neural network include the weight percentage of nine alloying elements and the heat treatment conditions such as austenitization temperature and isothermal transformation temperature and time. For the model development, 15 steels from the literature were used. The developed model was validated with respect to eight other steels from the literature that were not used for the model development. Additionally, the model was also employed to predict the hardness of five newly designed bainitic steels. Further, from the new experimental data, identifying the steel containing Co and Al as potentially viable for mass production, a computational analysis of this steel using the developed neural network model indicates the possibility of minimizing the processing costs by adjusting the alloying element content, Co in particular. [Copyright &y& Elsevier]

Abstract: The present work focuses on reverse modification of Al–5wt.%Ti–1wt.%B master alloy on the structural characteristics and mechanical properties of hypoeutectic ZnAl4Y alloy. The results shows that with the increase of the adding amount of master alloy to ZnAl4Y alloy, the morphology and the kind of primary phase as well as the amount of eutectic structure of the modified alloy vary considerably. With the increase of the adding amount of Al–5wt.%Ti–1wt.%B, the tensile strength and the hardness of modified ZnAl4Y alloy increase. When the adding amount is 0.5wt.%, the impact toughness and the elongation of the alloy reach the maximum. [Copyright &y& Elsevier]

Abstract: The aim of this study was to determine the effect of the maleic anhydride grafted polypropylene (PP-g-MAH) on the properties of short carbon fiber (CF) reinforced polypropylene (PP) composites. The composites were prepared by melt blending and injection molding techniques at different percentages of CF. Tensile tests, hardness, differential scanning calorimeter (DSC) and scanning electron microscopy (SEM) were performed to characterize the physical and morphological properties of the prepared composites. It was observed from SEM photographs that modification with PP-g-MAH improved the interfacial adhesion between the carbon fibers and PP matrix. The ultimate tensile strength, hardness and modulus values of modified PP composites were higher compared to the values of CF reinforced PP composites. Melting temperature of all composites was not changed significantly with increasing CF content; however degree of crystallinity values were decreased with the increasing CF content level. [Copyright &y& Elsevier]

Abstract: The present work deals with studies on the manufacturing and investigation of mechanical and wear behavior of aluminum alloy matrix composites (AAMCs), produced using powder metallurgy technique of ball milled mixing in a high energy attritor and using a blend–press–sinter methodology. Matrix of pre-mechanical alloyed Al–4.5wt.% Cu was used to which different fractions of nano and micron size TiC reinforcing particles (ranging from 0 to 10wt.%) were added. The powders were mixed using a planetary ball mill. Consolidation was conducted by uniaxial pressing at 650MPa. Sintering procedure was done at 400°C for 90min. The results indicated that as TiC particle size is reduced to nanometre scale and the TiC content is increased up to optimum levels, the hardness and wear resistance of the composite increase significantly, whereas relative density, grain size and distribution homogeneity decrease. Using micron size reinforcing particulates from 5% to 10wt.%, results in a significant hardness reduction of the composite from 174 to 98HVN. Microstructural characterization of the as-pressed samples revealed reasonably uniform distribution of TiC reinforcing particulates and presence of minimal porosity. The wear test disclosed that the wear resistance of all specimens increases with the addition of nano and micron size TiC particles (up to 5wt.%). Scanning electron microscopic observation of the worn surfaces was conducted and the dominant wear mechanism was recognized as abrasive wear accompanied by some delamination wear mechanism. [Copyright &y& Elsevier]