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It is challenging to tailor the mechanical properties of in-situ formed β phases in Ti/Zr-based bulk metallic glass composites (β-type BMGCs) without changing the morphologies of the β phases. Recently, BMGCs containing metastable β-Ti/Zr phases (metastable β-type BMGCs) exhibit an exothermic reaction below the glass transition temperature (sub- T g ) of the glassy matrices during heating, however, the corresponding structural origin remains unclear. In this work, the precipitation of ω phase inside β phase was revealed to account for the sub- T g exothermic event of the metastable Ti 45.7 Zr 33 Cu 5.8 Co 3 Be 12.5 BMGC. The sub- T g annealing of metastable β-type BMGCs causes the precipitation of nanometer-sized isothermal ω phase, which leads to a large increase in the modulus and hardness of the crystalline phase. This finding provides a novel route to tailor the modulus and hardness of the crystalline phases in BMGCs without changing their morphologies, including volume fractions, sizes, and distributions. On this basis, the influence of the modulus and hardness of the crystalline phase on mechanical properties of BMGCs was exclusively investigated. Our experimental results together with finite-element simulations proved that lower modulus and hardness of the crystalline phase benefit a larger plasticity of BMGCs. [ABSTRACT FROM AUTHOR]

Authors investigated mechanical properties of microcrystalline Fe 89−x Hf 4 Ta 1 Cu 1 Gd 1 Si x B 4 (x = 0–15) and Fe 74 Hf 4 Ta 1 Cu 1 Gd 1 La y Si 15−y B 4 (y = 7) alloys obtained by copper mold injection casting to a form of rods, 3 mm in diameter. Structure of the samples was analyzed by Cu K- α powder X-ray diffractometry and the unit cell parameters of identified h-Fe 2 Hf 0.8 Ta 0.2 (C14 Laves), fcc-Fe 16 Hf 6 Si 7 (D8 a ) and bcc-Fe phases were calculated. The study revealed that ascending Si content leads to reduction in values of both unit cell parameters of C14 phase in the alloys studied while causes the expansion of D8 a lattice; decrease in secondary dendrite arm spacing in the middle of the rods; stepwise improvement of yield and compressive strength at the expense of plastic deformation region, what was attributed to the precipitation of C14 Laves/D8 a in the interdendritic regions of bcc-Fe; decrease in flexural strength with no effect on deflection-at-yield and exponential increase in hardness of the studied alloys. There is also clear correlation between unit cell volume of fcc-Fe 16 Hf 6 Si 7 phase, yield and compressive strength on Si content. For the alloys with x = 0–13, relation between yield strength and Vickers hardness was described with logarithmic function. It was found, that the lattice expansion of bcc-Fe and, in lesser extent, C14 Laves phase is correlated with the value of bending modulus in the whole composition range. [ABSTRACT FROM AUTHOR]

A linear single variable model for describing precipitation heat treated Al-Zn-Mg-Cu aluminium alloy hardness and yield strength based on precipitate compositions was proposed. A concept composition model was developed based on the major alloying elements and the strengthening precipitate compositions, for the precipitation heat treatment condition. A Refined composition model was subsequently developed to account for the effect of minor alloying (Mn) and impurity elements (Fe, Si). Macro segregation of alloying elements had a significant effect on the results of the Refined composition model. Mechanical properties varied according to a simple linear relationship with the atomic fraction of the strengthening precipitate. The T6 and T73 hardness, and T6 yield strength were algebraically expressed, with linear relationships. The model describes existing yield strength data for Al-Zn-Mg-Cu aluminium alloys. The Refined composition model was also valid for predicting yield strengths of Al-Zn-Mg-Cu-Zr aluminium alloys in the T6 condition. [ABSTRACT FROM AUTHOR]

In this paper hybrid welding of the annealed AA5754 alloy was studied and the role of post weld heat treatment (PWHT) on microstructure and mechanical properties was investigated. The microstructure and hardness of the base material and welds were analyzed. Due to the segregation, the lowest microhardness value was observed at the welding centerline. High microhardness was registered in a narrow zone at the interface between the fusion zone and the heat affected zone where the welding cycle promotes both the strengthening by Mg solid solution and the lowest grain size. The hardness of the heat affected zone was higher than that of the base material due to dissolution of soluble particles (Mg2Si and Mg2Al3). PWHT at 350 °C increased the microhardness in the fusion zone and the tensile strength with respect to the untreated joint, whereas the strain at fracture was similar showing that the fracture was promoted mainly by the presence of porosity, coarse grain size and insoluble segregated second phases. [ABSTRACT FROM AUTHOR]

This study systematically investigated the microstructural evolution, hot workability, and mechanical properties of the β-γ TiAl alloy Ti-43Al-2Cr-2Mn-0.2Y. The as-cast alloy had a wide hot working window and excellent hot workability. A crack-free pancake was obtained through one-step canned forging with an initial deformation condition of 1200 °C/0.1 s- 1. The coarse lamellar microstructures of the as-cast alloy were broken down into fine γ grains after forging. Residual lamellae were hardly observed even near the edge of the pancake. Dynamic recrystallization of γ grains was the main softening mechanism during hot forging. Tensile tests showed that the as-forged alloy exhibited better room temperature tensile properties than the as-cast alloy because of microstructural refinement and homogenization. The ultimate tensile strength of the as-forged alloy at 700 °C was maintained at 496 MPa, and elongation was 10%. The ductile-brittle transition temperature was between 700 and 750 °C. In addition, the nano-hardness values of the β0 and γ phases were 5.6 and 4.6 GPa, respectively. The hardness of the β0 phase was lower than that of the β0 phase in TNM alloys, indicating that the hardness of the β0 phase highly depended on alloying elements. [ABSTRACT FROM AUTHOR]

The effect of chemical bonding on the mechanical properties of high-temperature materials remains a big challenge. In this paper, the relationship between Si concentration and mechanical properties for Nb-Si compounds was investigated by first-principles calculations. One previously unreported crystal structure of Nb2Si with Ta2Si-type structure was predicted. The elastic properties, hardness and chemical bonding of Nb-Si compounds were calculated in detail. The calculated formation enthalpy shows that Nb5Si3 is more stable than that of other Nb-Si compounds at the ground state. The obtained shear modulus, Young's modulus and hardness of Nb-Si compounds increase with increasing Si concentration. NbSi2 exhibits the strongest shear deformation resistance and the biggest hardness among these Nb-Si compounds. It thus can be concluded that the variation of elastic properties depends not only on the Si concentration but also on the chemical bonding. With increasing Si concentration, Nb-Nb metallic bond is disappeared and Si-Si covalent bond is formed. [ABSTRACT FROM AUTHOR]

This paper demonstrates the successful processing of a high-strength Fe85Cr4Mo8V2C1 tool steel by selective laser melting (SLM). Based on tailored parameter variation studies, crack-free and highly dense FeCrMoVC parts (99.99% relative density) are obtained by this processing method. The applied localized high heat inputs during very short interaction times result in a fine, homogeneous microstructure composed of martensite, austenite, and carbides. This combination of phases together with the morphology of the microstructure results in excellent mechanical properties, such as a microhardness of 900 HV 0.1 (ca. 67 HRC) and a compressive strength of about 3800 MPa combined with a fracture strain up to 15%. Therefore, the SLM processing of this alloy enables a further increase of the hardness and compressive strength compared to the as-cast state. Altogether, processing the FeCrMoVC steel by SLM as one key additive manufacturing technology shows high potential for advanced tool design. [ABSTRACT FROM AUTHOR]

This work addresses the numerical correlation of the factors that may affect the hardenability of AISI 1045 steel submitted to the Jominy end-quench test in three austenitizing temperatures: 20 °C, 70 °C and 120 °C above the critical temperature (A c3 ) according to the CCT diagram (Continuous Cooling Transformation). Thermocouples were placed in the specimens at predefined points to obtain cooling curves during the Jominy end-quench test. Metallographic analysis and the Jominy hardness profiles (using the Rockwell C method) allowed evaluating the hardenability in function of the austenitizing temperatures. Calculation of the percentage of phases presented in the microstructures and Vickers microhardness tests at these phases and micro-constituents were applied to obtain numerical expressions to correlate the phase percentages and hardness profiles according to the cooling rate variations during the test. Subsequently, equations were obtained by regression numerical methods to estimate the amount of phases and micro-constituents (martensite, bainite, pearlite and ferrite) formed during the test, and also to estimate the hardness profile. [ABSTRACT FROM AUTHOR]

In this study, Spark Plasma Sintering (SPS), a relatively fast consolidation method assisted with simultaneous application of heat and pressure, was used to produce bulk carbides from mixed WC–7.5 wt% Nano Co powders. Different pressures ranging from 30 to 80 MPa were applied during sintering to explore its effect on the mechanical properties of resulting carbides. The maximum hardness was found for the samples pressed at 80 MPa, which is ∼1925 HV (18.88 GPa), higher than that of the commercially available cemented carbide tools. The marked changes in porosity, hardness, and crack propagation observed in the samples show that the sintering pressure have considerable impact on the mechanical properties of cemented carbides. In particular, the nature of crack initiation and propagation, which is indicative of the fracture toughness of materials, was studied and clarified. [ABSTRACT FROM AUTHOR]

The mechanical and tribological properties of the Fe–15.88Al–5.46Cr (wt.%) based composites reinforced with 15, 25, 35 wt.% novel W 0.5 Al 0.5 C 0.5 particulates (referred to FA15, FA25 and FA35), produced by hot-press sintering, were evaluated. The hardness of the composites increased with the W 0.5 Al 0.5 C 0.5 content but the bending strength firstly decreased and then increased. The wear resistance of the composites was dramatically superior to Fe–15.88Al–5.46Cr alloy (FA0) without mass density gain. Interestingly, the wear resistance increased with W 0.5 Al 0.5 C 0.5 concentration from 15 to 25 wt.%, but then slightly declined when W 0.5 Al 0.5 C 0.5 content was up to 35 wt.%. It is also surprised that FA25 displayed the lowest friction coefficient, while that of other composites was much higher than Fe–15.88Al–5.46Cr alloy. These abnormal mechanical and tribological behaviors would be associated with the microstructure of the composites and the composition of the worn surfaces. The wear mechanism of the composites was abrasion and oxidation wear. [ABSTRACT FROM AUTHOR]

Highlights: [•] Directionally solidified ZrO2-mullite eutectic grown by laser floating zone. [•] Ultra-fine eutectic morphology. [•] A remarkable hardness value of 21.2GPa for the fastest as-grown fibres. [Copyright &y& Elsevier]

Highlights: [•] Designing a net hole was effective to achieve uniform distribution SiC particles and prevent agglomeration of them. [•] SZ has fine and equiaxed grains and distribution of SiC particles in the matrix is almost uniform. [•] No intermetallic compound was formed after FSP. [•] In comparison to pure Cu, Cu/SiC composite shows higher hardness and better wear behavior. [Copyright &y& Elsevier]

Highlights: [•] Enhanced static mechanical properties for MWCNT-PC composite for minor MWCNT compositions. [•] Variation of hardness and elastic modulus with change in MWCNT composition in the composite. [•] Use of Nano-Indentor to extract nano scale properties. [•] Simple methodology for composite fabrication and composition comparison. [Copyright &y& Elsevier]

Highlights: [•] Secondary hardening occurred when tempered at 500°C and austenitized at 1050°C. [•] Hardness of new steel is about 1 HRC higher than D3 steel, when tempered at 300°C. [•] New steel has less bending strength and strain compared with D3 steel. [•] With increasing hardness wear resistance is improved about 56%. [•] Linear relationship observed between weight loss and hardness of modified steel. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cu–P composite with micro and nano-SiC were deposited by electroless plating. [•] The coatings showed crystallisation structure. [•] The size of SiC particles did not change the structure of coatings. [•] Cu–P/nano-SiC coatings showed the best chemical, physical and mechanical properties. [Copyright &y& Elsevier]

Highlights: [•] Effects of the B contents on the peak load of the RSW in CP steels were examined. [•] The ND increased with increasing current regardless of the B contents. [•] Load in PF mode was affected by both the min. hardness and fractured diameter. [•] Load in IF mode was dependent only on the fractured diameter. [•] ND<5t 1/2 resulted in IF mode regardless of the B contents. [Copyright &y& Elsevier]

Highlights: [•] Functionally graded steel and nickel super-alloy structures have been developed. [•] Mechanical properties of FGMs can be controlled by process input parameters. [•] SDAS is strongly dependent on the laser power and powder mass flow rate. [•] Carbides provide a mechanism to control the hardness and wear resistance of FGM. [•] Tensile strength of FGM is dependent on the laser power and powder mass flow rate. [Copyright &y& Elsevier]

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: [•] 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: [•] 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: [•] 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: [•] 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 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 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: 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: 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: 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 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]

Abstract: The present work was carried out to investigate the effect of long-term service exposure on microstructure and mechanical properties of a gas turbine hot gas path component, made of Alloy 617. The results showed significant service-induced microstructural changes, such as excessive grain boundary Cr-rich M23C6 carbides formation and some oxidation features in the exposed material in compare with the solution-annealed material. Also it was found that the yield strength and hardness of the alloy have increased while the ductility of the alloy has decreased. In the similar test conditions, the stress-rupture life of the exposed alloy decreased considerably compared to the solution-annealed sample, which could be attributed to the microstructural degradation, especially formation of continuous M23C6 carbides on grain boundaries. [Copyright &y& Elsevier]

Abstract: Particles of TiCN and TiC were produced by means of self-spreading high temperature synthesis and after covering with metal protector were studied in order to be applied for modification of molten steel. After microstructure characterization the TiCN nano- and micron-sized particles were selected for modification of castings of P265GH steel and the microstructure and mechanical properties of the modified steel were studied and compared with those of the steel without modification. The data from microstructure-properties analysis of the modified steel showed that the steel treated with nano- and micro-sized particles has significantly refined microstructure, increased strength and hardness and improved elongation in comparison with the non-modified castings. [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: The effects of deep cryogenic treatment (DCT) on the static mechanical properties of the AISI 302 austenitic stainless steel were investigated through experimental testing. The results of the tensile and hardness tests are discussed and compared to data and microstructural observations from the DCT literature concerning the same class of steel. In addition, the influence of two important treatment parameters, such as the soaking-time and the minimum temperature, is analysed through a full factorial design of experiments (DOE) and by means of a first approximation model in order to obtain confirmation and suggestions about the possible use of the DCT as a standard practice to improve the mechanical properties of stainless steels. A particular focus is given to the registered changes of the elastic modulus and of the hardness as representative measures of two different deformation mechanisms. [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: Ti–47Al–2.5V–1Cr and Ti–40Al–2Cr (at.%) intermetallic alloys was fabricated by the laser melting deposition (LMD) manufacturing process. The microstructure was characterized by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The room-temperature (RT) tensile properties and Vickers hardness of the as-deposited and heat-treated specimens were evaluated on longitudinal directions. Results shows that full density columnar grain with fully lamellar (FL) microstructure consisted of γ-TiAl and α2-Ti3Al was formed in the as-deposited γ-TiAl samples. The room-temperature tensile strength of the as-deposited Ti–47Al–2.5V–1Cr alloy is up to approximately 650MPa in the longitudinal direction and 600MPa for the as-deposited Ti–40Al–2Cr alloy, while the tensile elongation is approximately 0.6% at most. Different microstructure types were obtained in the Ti–47Al–2.5V–1Cr and Ti–40Al–2Cr alloy after heat treatment. The stress–strain curve and the tensile fracture sub-surface indicate that the fracture manner of the as-deposited and heat-treated specimens was inter-granular manner. [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: AA5454-O aluminum alloy has been flat rolled as cold, warm and hot conditions for various temperature and deformation rates. The changes in microstructure and mechanical properties have been determined through tensile, hardness and microscopic analysis. Microscopic observations were made through optical and scanning electron microscopes and X-ray analysis was also conducted. The temperature and deformation rate had great influence on microstructure and fracture type of cold, warm and hot rolled alloy. The strain hardening exponent (n) decreased, and strain rate sensitivity exponent (m) increased with increasing process temperature and deformation rates. The hardness increased with increasing deformation rate and temperature, but reached to a maximum for 200°C and 50% deformation. [Copyright &y& Elsevier]

Abstract: Sintered and forged low-alloy P/M steels containing Cr, Ni and Mo were subjected to tensile, hardness and impact tests, in order to understand the influence of the alloying elements and microstructure on their mechanical properties. Elemental powders of atomized iron, graphite, chromium, nickel and molybdenum were mixed in suitable proportions using a ball mill, compacted and sintered in order to yield the following alloy compositions: Fe–0.2%C, Fe–0.2%C–1%Cr, Fe–0.2%C–1%Cr–2%Ni, Fe–0.2%C–2%Ni and Fe–0.2%C–2%Ni–1.5%Mo. Cylindrical compacts of 24mm diameter and 32mm height were prepared from the powder mixes in a 1000kN hydraulic press using suitable cylindrical die-punch combination. Sintering of the ceramic-coated cylindrical preforms was carried out at 1000±10°C in a muffle furnace for a period of 120min. Immediately after sintering, the cylindrical compacts were hot upset forged and drawn into square cross-section bars of density values to near-theoretical using a 2000kN friction screw press. The size of the bars was maintained as 10×10×110mm for preparing tensile specimen and 12×12×70mm for impact specimen. Standard tensile and impact specimens were machined off from the forged square rods. Standard procedure was followed for conducting tensile test and impact test on the forged alloys. Hardness of the hot forged alloys was also measured using Rockwell hardness tester. Microstructures of the alloys were examined for correlating with the mechanical properties. Fractographs of the fractured surfaces of the tensile specimens were obtained using a scanning electron microscope. From the present study, it is contended that the alloying elements Cr, Ni and Mo have strong influence on the tensile and impact properties of the low-alloy steels studied. Among all the five alloys considered, the steel with chromium addition has exhibited the highest tensile strength with the corresponding impact strength being the least. The same alloy has also been found to have the highest hardness value, compared to the rest of the alloys. The plain carbon steel specimens exhibit a ferrite–pearlite structure whereas carbides of Cr and Mo were observed along with ferritic and bainitic microstructure in the case of the hot forged alloys with Cr, Ni and Mo additions. [Copyright &y& Elsevier]

Abstract: In this study, the effect of artificial aging on the machinability of 6061 Al-alloy was investigated for the as-received, solution heat treated (SHT) and solution heat treated and then aged (SHTA) conditions. The experimental work has revealed that different aging times at 180°C and the cutting speed significantly affected the machined surface roughness values. However, cutting forces were not influenced significantly by aging and cutting speed except for SHT workpieces having the lowest hardness. [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: The effect of natural weathering on the mechanical, morphological and thermal properties on the high impact polystyrene (HIPS) and cold drawn HIPS are investigated. After natural weathering period of 8760h, under known meteorological parameters, the changes in mechanical properties are investigated by using tensile, instrumented impact and hardness tests. Thermo-mechanical properties are characterized by using thermomechanical analysis (TMA) and melt flow index (MFI). Fractured surfaces of the materials are investigated by scanning electron microscope (SEM). Natural weathering effects on fracture mechanisms are discussed by means of fractographical analysis. Remarkable morphological changes were observed especially at the surface of the material. This results in dramatic loss in mechanical properties. [Copyright &y& Elsevier]

Abstract: The system of heat-treatment operations, involved in the manufacture of alloy-steel axle-shafts, is reengineered and standardized to ensure quality-consistency as per international standards. The quality-engineering tool of Cause-and-Effect diagram/analysis is also applied in the reengineering technique. The heat-treatment temperatures and time-duration parameters are readjusted by their relationship to their mechanical properties. The Fe–Fe3C phase diagram was extensively referred in reengineering of the austenising temperature. The required hardness values were successfully achieved in the heat-treated axle-shafts as a result of this reengineering research and development. [Copyright &y& Elsevier]

Abstract: A study on the effect of squeeze casting parameters on the mechanical properties of AZ91Mg alloy with 2wt.% Ca incorporated was conducted. The parameters studied include squeeze casting pressure, melt temperature and mould temperature. It was found that a squeeze casting pressure of 111MPa and a melt and mould temperature of 800°C and 200°C respectively gave a good combination of tensile and hardness properties in AZ91–2Ca Mg alloy. This was due primarily to the effective mould filling, microstructural refinement and good heat transfer between the molten metal and the mould. [Copyright &y& Elsevier]