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The hardness, strength, and abrasion resistance of copper for electrical contact materials is poor. Thus, we aligned carbon nanotubes in Cu matrix composites through die-stretching for their excellent mechanical properties and abrasion resistance. The Cu matrix composites with varying CNTs volume fraction from 0 to 10 vol.% were fabricated under protective atmosphere sintering of a mixture of Cu powders and Ni/Cu coated CNTs. This was followed by forging and die-stretching. The CNTs were uniformly dispersed in the dense composites, and the trend of their alignment along the stretching direction was obvious. The composites were anisotropic, and their mechanical properties and abrasion resistance increased obviously with the addition of CNTs. The 5 vol.% CNTs/Cu composite showed the best hardness, tensile strength, and abrasion resistance. The mechanisms underlying the improved mechanical and tribological behavior were evaluated, and this research provides novel ideas and technology for the distribution and directional alignment of CNTs in the matrix. [ABSTRACT FROM AUTHOR]

Low-activation structural materials for fusion applications beyond 700 °C are desired. High-entropy alloys (HEAs) with excellent properties at elevated temperatures are suitable for use in nuclear reactors. A newly developed V 35 Ti 35 Fe 15 Cr 10 Zr 5 HEA was fabricated by vacuum arc melting and the microstructure of as-cast and annealed sample was found to be composed of BCC solid solution phases. It was interesting to find that the yield strength of as-cast V 35 Ti 35 Fe 15 Cr 10 Zr 5 HEA increased with increasing the temperature below 500 °C, and it was much higher than that of vanadium alloy or martensitic steel for fusion reactors in the temperature range of room temperature to 900 °C. At 700 °C, the yield strength of V 35 Ti 35 Fe 15 Cr 10 Zr 5 HEA was about 500 MPa higher than that of vanadium alloy or martensitic steel, showing promise for high temperature applications. V 35 Ti 35 Fe 15 Cr 10 Zr 5 alloy had a relative low ductility below 700 °C, while the alloy exhibited a good ductility above 700 °C. [ABSTRACT FROM AUTHOR]

Cr12MoV has wide applications in the molds and dies industry. However, it is also a hard-to-machining material due to its high mechanical strength and hardness. Area ablation of Cr12MoV cold-work mold steel was carried out using a picosecond (ps) pulse Nd:YVO 4 laser. The effects of laser fluence and wavelength on the ablation rate and machining quality were investigated with wavelengths of 1064 nm, 532 nm and 355 nm. The experimental results indicate a logarithmic increase of the ablation rate to a maximum value of ~ 41 nm/pulse with the increase of laser fluence using the wavelengths of 1064 nm and 355 nm. For the wavelength of 532 nm, an ablation rate of ~ 33 nm/pulse is achieved at low laser fluence of 8.28 J/cm 2 , then increases logarithmically into about 54 nm/pulse at 25.10 J/cm 2 , and then decreases steeply into almost zero as the laser fluence increases above 25.10 J/cm 2 . For the three laser wavelengths, different pore sizes were observed in the laser ablation region. The surface roughness increases exponentially with the increase of the laser fluence. The influence mechanisms of laser fluence and wavelength on the laser ablation rate and machining quality were systematically analyzed and discussed in this paper. [ABSTRACT FROM AUTHOR]

In the present study, powder metallurgy processed unmilled AlMg5 (AlMg5-UM), milled AlMg5 (AlMg5-M), and milled AlMg5–0.4 vol.% Al 2 O 3 (AlMg5–0.4Al 2 O 3 ) nanocomposite were successfully spark plasma sintered at 550 °C. The microstructural analysis of spark plasma sintered AlMg5-UM revealed equi-axed grains with average size of 20 ± 5 μm. The microstructural analysis of spark plasma sintered AlMg5-M and AlMg5–0.4Al 2 O 3 revealed a bimodal grain structure with both fine-coarse grains of size 700 nm–8 μm and 300 nm–8 μm, respectively. The spark plasma sintered AlMg5-UM exhibited a yield strength (YS) of 132 ± 3 MPa, ultimate tensile strength (UTS) of 296 ± 2 MPa and % elongation (% El) of 22 ± 2 comparable to the conventional Al 5083 alloy — O temper (YS of 145 MPa, UTS of 281 MPa and % El of 16). The spark plasma sintered AlMg5-M and AlMg5–0.4Al 2 O 3 exhibited YS of 242 ± 9 MPa and 274 ± 5 MPa, UTS of 376 ± 4 MPa and 417 ± 8 MPa and % El of 19 ± 1 and 10 ± 1, respectively. The lower strength (YS and UTS) of AlMg5-UM can be ascribed to its coarse grains. Among the milled samples, the AlMg5–0.4Al 2 O 3 composite exhibited high strength and it can be ascribed to its fine grain size (Hall–Petch effect), higher dislocation density and Orowan strengthening effect due to Al 2 O 3 reinforcements. [ABSTRACT FROM AUTHOR]

Abstract: Fabrication of metal-based composites with concurrent grain refinement is an exciting and novel avenue in hybrid metal manufacturing. Copper clad aluminum rods, that were fabricated using Axi-Symmetric Forward Spiral Composite Extrusion (AFSCE) are investigated here as an example. Careful investigations of the bonding mechanism in the AFSCE samples are needed to control mechanical and physical properties of the composite material. In order to understand the mechanism of the bonding between copper and aluminum in the AFSCE process, morphological and micro-structural investigations were conducted by using a Scanning Electron Microscope/Focused Ion Beam (SEM/FIB) dual ion microscope and X-ray diffraction to study the nature of the interface. Hardness measurements across the interface region of the AFSCE sample were also produced to examine the deformation mechanism. A near flawless interface, without significant intermetallic or oxide layer, was identified. The strength variation in the copper region was characterized using micro-hardness tests which agreed well with the Electron Backscatter Diffraction (EBSD) observations of various sampling points. It was also found that the micro-hardness values near the interface and the outer periphery regions of the copper were higher than the hardness values at the middle region of the material, which is approximately equal to that of unprocessed copper. [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: [•] 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 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: [•] 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]

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: 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: 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: 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: A study has been conducted to investigate the mechanical and wear behaviors of the Al–12Si–XMg alloys (where Mg contents were 5%, 10% and 20%) cast by adding modifiers such as Sr, red phosphorous and salt mixtures. Mechanical properties were determined by hardness measurements, compression and wear tests. Reciprocating wear tests were conducted by rubbing ceramic (Al2O3) and steel (AISI 52100) balls on the unlubricated surfaces by applying the normal load of 2N. The microstructure of the Al–12Si–XMg alloys consisted of the Si needles and Mg2Si precipitates (two morphologies of which are polyhedral shape dark particles and grey colored components of Chinese script) in the Al matrix. Results demonstrated that volume fraction and size of the primary Mg2Si particles increased with increasing the Mg content. Mg containing alloys exhibited higher hardness and better wear resistance than the Mg free alloy. [Copyright &y& Elsevier]

Abstract: Underwater friction stir welding (underwater FSW) has been demonstrated to be available for the strength improvement of normal FSW joints. In the present study, a 2219 aluminum alloy was underwater friction stir welded at a fixed rotation speed of 800rpm and various welding speeds ranging from 50 to 200mm/min in order to clarify the effect of welding speed on the performance of underwater friction stir welded joint. The results revealed that the precipitate deterioration in the thermal mechanically affected zone and the heat affected zone is weakened with the increase of welding speed, leading to a narrowing of softening region and an increase in lowest hardness value. Tensile strength firstly increases with the welding speed but dramatically decreases at the welding speed of 200mm/min owing to the occurrence of groove defect. During tensile test, the joint welded at a lower welding speed is fractured in the heat affected zone on the retreating side. While at higher welding speed, the defect-free joint is fractured in the thermal mechanically affected zone on the advancing side. [ABSTRACT FROM AUTHOR]

Abstract: Aluminum matrix composite is one of the most conventional types of metal matrix composites. This paper deals with the effect of production parameters on wear resistance of Al–Al2O3 composites. Alumina powder with a particle size of 12, 3 and 48μ and pure aluminum powder with particle size of 30μ were used. The amount of added alumina powder was up to 20%. Ball milling was utilized to blend the powders. The range of sintering temperature and time were 500, 550 and 600°C and 30, 45, 60 and 90min respectively. It was found that increasing sintering temperature results in increasing density, hardness and wear resistance and homogenization of the microstructure. However at certain sintering temperatures and time, considerable grain growth and reduction of hardness value occurred, leading to the degradation of wear resistance. The results showed that at high alumina content, relative density of the composite increases. However, after raising the particle size of alumina, relative density initially increases and then drops to lower values. Increasing weight percent of alumina powder leads to higher hardness and consequently improves the wear resistance of Al–Al2O3 composite. The use of fine alumina particles has a similar effect on hardness and the wear resistance. Finally, a finer grain size was observed, at high amount and low size of the reinforcement particle. [Copyright &y& Elsevier]

Abstract: In friction stir welding (FSW), the material under the rotating action of non-consumable tool has to be stirred properly to get defect free welds in turn it will improve the strength of the welded joints. The welding conditions and parameters are differing based on the mechanical properties of base materials such as tensile strength, ductility and hardness which control the plastic deformation during friction stir welding. The FSW process parameters such as tool rotation speed, welding speed and axial force, etc. play a major role in deciding the weld quality. FSW Joints of cast aluminium alloys A319, A356, and A413 were made by varying the FSW process parameters and the optimum values were obtained. In this investigation, empirical relationships are established and they can be effectively used to predict the optimum FSW process parameters to fabricate defect free joints with high tensile strength from the known base metal properties of cast aluminium alloys. [Copyright &y& Elsevier]

Abstract: The thixoextrusion process is a new method for manufacturing complicated and net shape components through which high strength materials can be formed more easily. In this study 7075 Al alloy which has low extrudability has been thixoformed by forward extrusion process. As it is known conventional extrusion of 7075 Al alloy has been very difficult due to high strength and multi-phase microstructural characterization. In this research, by applying the advantages of semisolid processing, the applied pressure for extrusion is decreased and desired mechanical properties were reached near the standard predictable properties for wrought 7075 Al alloy under T6 tempering conditions, for example tensile and yield strength and hardness of samples of thixoextrusion product sufficiently agree with same expected properties of wrought 7075 Al alloy and only elongation is decreased along this process. [Copyright &y& Elsevier]

Abstract: This paper describes wear behavior of powder metallurgy (PM) 316L stainless steel with additions of elemental boron with the aim of producing superior mechanical properties. The wear test of the samples is conducted using a pin specimen of PM 316L stainless steel doped with elemental boron and a steel disc specimen with hardness of 180 HV10. Densification achieved with boron addition due to the liquid phase formation up to 95% of theoretical density with 0.6wt.% boron addition. Most mechanical properties such as hardness, tensile strength and yield strength were improved with boron addition. The wear rate of PM 316L stainless steel decreased from 4.3×10−6 to 0.8×10−6 mm3/Nm with the addition of 0.6wt.% elemental boron. The abrasive-induced delamination wear dominated at the samples. Scanning electron microscopy observations of the worn surfaces revealed that plastic deformation occurred with delamination of surface layers in the sintered conditions. [Copyright &y& Elsevier]

Abstract: Advanced high strength steels (AHSS) are essential to meet the demands of safety and fuel efficiency in vehicles. In this paper, we present the results of laser welding of two AHSS steels, TRIP780 and DP980. A 2kW Trumpf TRUDISK 6002® Yb:YAG laser beam was utilized to join 1mm thick TRIP780 with 1.5mm thick DP980 and 1mm thick mild steel. Optical metallography was used to characterize the weld profile and microstructures. Microhardness, tensile and fatigue tests were performed to evaluate the mechanical properties. Results indicate that the laser welds exhibit excellent strength and hardness with minimal defects which are attributed to the high beam quality, disk type of laser. In addition, there is a distinct effect of pre-straining of TRIP780 steels on the energy absorption. [Copyright &y& Elsevier]

Abstract: Surface modification of AISI 410 martensitic stainless steel was carried out by laser surface-melting using laser engineered net shaping (LENSTM). The microstructures of laser surface-melted specimens showed varying amount of retained austenite depending on the processing parameters. The refinement and high strength of austenite as a result of increased scan speed and decreased laser power resulted in high amount of retained austenite in the final microstructure. Laser surface-melting of AISI 410 martensitic stainless steel at optimized processing parameters resulted in fine martensite with minimum retained austenite, leading to a 55% increase in the surface hardness compared to the hardness of conventionally heat treated samples. The inherent advantage of laser surface-melting using LENSTM is to control simultaneously both location and microstructure leading to better service performance of components. [Copyright &y& Elsevier]

Abstract: In consideration of the raising interest about the application of the deep cryogenic treatment (DCT) on materials, its effects on the static mechanical properties of a commercial gear carburized steel (18NiCrMo5) are investigated through hardness and tensile tests followed by optical fractographic observations. The present study focuses on the comparison between the results given by different sequences of DCT and tempering performed after the conventional case hardening. In addition, the soaking time parameter influence is analyzed for the case of the pre-tempering DCT. A special attention is paid to the statistical analysis of the experimental data in order to avoid misinterpretations. The results point out substantial hardness increases (from +0.6 HRC to +2.4 HRC) for all the cryotreated groups and a remarkable enhancement of the tensile strength (+11%) in one case, indicating that different sequences and DCT parameters must be considered depending on the application requirements. The experimental results are then discussed in consideration of the literature about the DCT on similar steels with the aim of correlating the obtained improvements to the microstructural mechanisms that are commonly ascribed to this treatment. [Copyright &y& Elsevier]

Abstract: In the present paper, the microstructure, compressive properties at different temperatures and hardness of NiAl–Cr(Mo)/Nb alloy prepared by injection-casting were investigated. Compared with the conventionally cast alloy, the injection-cast alloy exhibited a fine microstructure, i.e. the fine eutectic cell and interlamellar spacing as well as fine primary NiAl phase and Laves phase Cr2Nb due to the high cooling rate. In addition, the area fraction of primary NiAl phase at the cell interior or cell boundaries and eutectic cell increased. The compressive ductility and yield strength at room temperature increased by about 100% and 50% over those of conventionally cast alloy, respectively. However, both alloys possessed the similar high temperature strength. The Vickers hardness of injection-cast alloy also increased markedly. [Copyright &y& Elsevier]

Abstract: The purpose of present study was to investigate a cheap method to manufacture particleboard. The experiments were carried out using almond shell that had no economical value other than being used merely as low grade fuel and fodder. The parameters affecting composite particleboard production from almond shell and urea–formaldehyde were determined to be urea–formaldehyde ratio, reaction temperature, reaction time and almond shell particle size and the effect of these parameters on hardness and bending strength were investigated. The experimental results showed that maximum hardness and bending strength were 97.5 Shore A and 84.52N/cm2, respectively, at a urea–formaldehyde ratio of 0.97, reaction temperature of 70°C, reaction time of 25min and mean particle size of 0.3mm. [Copyright &y& Elsevier]

Abstract: The effects of carbon content on the microstructures, mechanical properties and wear behavior of high vanadium (10%) high speed steel were studied systemically. The results show that the carbides in high vanadium high speed steel are composed of the vanadium carbide, small amount of Cr composite carbide and Mo composite carbide. With the increase of the carbon content, the amount of carbides increases obviously, the shape of carbides is changed from rod, strip to bulk, spherical, and the microstructures of metallic matrix are transformed from the ferrite, the mixture of ferrite, the martensite and retained austenite to the martensite and retained austenite. The hardness and the wear resistance of high vanadium high speed steel are increased, but its impact toughness would be decreased. [Copyright &y& Elsevier]

The effect of different artificial aging heat treatment on the quality of A357 alloy cast ingot specimens is evaluated. The experiments include artificial aging of the specimens at 155, 175 and 205 °C for various aging times. The dependencies of hardness and tensile properties of the aged alloys on the aging conditions are derived. Rockwell hardness and yield strength could be correlated using a linear function. The material quality is evaluated such as to be application-specific. By relating quality to yield strength quality could be assessed using the Rockwell hardness measurements. To account in quality evaluation also for tensile ductility quality indices are exploited. The dependencies of the involved quality indices on the aging conditions are derived. Same values of the same quality index are found to correspond to different combinations of tensile properties. The quality index QD proposed by the authors is exploited to devise quality maps; they involve iso-quality lines and the corresponding combinations of tensile properties. A quality map for the cast ingot of A357 alloy is presented. The map may be exploited to select the aging conditions such as to tailor the alloy properties to a certain engineering application. [Copyright &y& Elsevier]

Abstract: Aluminum (Al) matrix composites reinforced with 0–2.0wt.% multi-wall carbon nanotubes (MWCNTs) were prepared by thorough mixing of the composite powders in a roller mill and then sintered using a spark plasma sintering (SPS) machine followed by hot extrusion. Fully dense Al–MWCNT composites were obtained. The microstructure and mechanical properties of these composites were characterized: there is a significant enhancement in the Al–MWCNT composite properties at initial loadings 0.5wt.% of MWCNTs when compared to Al samples without much increase in cost. [Copyright &y& Elsevier]