The purpose of this study was to investigate the tensile properties and plasticity of semi-solid 6061 Al alloy at room and elevated temperatures. The semi-solid 6061 alloy was produced by the Gas Induced Semi-Solid (GISS) technique followed by squeeze casting process. The conventional liquid squeeze cast (CLC) 6061 alloy was also fabricated for comparison. The tensile tests were performed at temperature of 25 °C, 100 °C and 175 °C. The experimental results showed that the UTS, 0.2% yield strength and % elongation at break of the SSM alloy are higher than those of the CLC one at all temperatures. Based on the simple flow law, σt=Kεtn , the strain hardening exponentnand the strength coefficientKof the SSM alloy are lower than those of the CLC. The SSM alloy demonstrates more plasticity than the CLC. The results may be attributed to the more globular structure of the SSM alloy.
17-4 PH stainless steel is commonly used in sev eral engineering applications because of the combined good mechanical properties and high corrosion resistance. Metal injection moulding (MIM) was used to fabricate 17-4 PH stainless steel specimen with three mean powder sizes (D50), which are 2.82, 4.04 and 12.65 μm. The rheology of three feedstocks were investigated using melt flow index (MFI) and viscosity analysis. Feedstocks were injected at 170 °C. Injected tensile specimens were sintered at 1325 °C for 2 h in argon atmosphere. Surface roughness (Ra) measurement, relative density measurement, tensile test and hardness test (HRC) were carried out. Corrosion properties were determined by cyclic polarisation tests. The results indicated that the relative density of sintered samples is higher than 98% (7.68-7.74 g/cm3). α-Fe (bcc-martensite), δ-Ferrite (delta ferrite) and also SiO2 were observed in all sintered samples, which were detected by scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDS). As the mean powder size of injected specimens increases, the elongation and hardness increase, whereas the ultimate tensile strength (UTS) and surface roughness decrease. Moreover, the specimens using the smallest powder (2.82 μm) have shown better corrosion resistance than the specimens using the larger powders as the higher potentials in term of E-pit (the potential of pitting) and E-rep (the potential of repassivation) and the lower potential in term of E-cor (the potential of corrosion).
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