Iranian Journal of Materials Science and Engineering

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Combustion synthesis is a special thermophysico-chemical process applied for production of intermetallic compounds. In the present work, a reaction–diffusion numerical model was developed to analyze the combustion synthesis of aluminide intermetallics by self-propagating high-temperature synthesis process. In order to verify the reliability of the numerical model, an experimental setup was designed and used to perform the combustion synthesis of nickel and titanium aluminides. The developed model was further used to determine the temperature history of a powder mixture compact during self-propagating high-temperature synthesis. The effect of compact relative density on combustion temperature and wave propagation velocity was also studied.

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Abstract: This study presents the research results of effect that refining process has on porosity and mechanical properties of high pressure die castings made of AlSi12S alloy. The operation of refining was carried out in a melting furnace with the use of an FDU Mini Degasser. Mechanical properties (UTS, YS, Elongation, Brinell Hardness) were assessed on samples taken from high pressure die castings. The effect of molten metal transfer operation and the time elapsing from completion of the refining process on the alloy mechanical properties was determined.

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The probable reasons for evolution of weld porosity and solidification cracking and the structure- property relationship in aluminium welds were investigated. Aluminium plates (1xxx series) were welded by Tungsten Inert Gas (TIG) welding process, 5356 filler metal was used and heat input was controlled by varying welding current (145A, 175A and 195A). The welded samples were examined under optical and scanning electron microscopes and mechanical tests were performed to determine tensile and impact strengths. Secondary phase, identified as globules of Mg2Al3 precipitates, was found to be formed. Solidification cracking appeared in the heat affected zone (HAZ) and porosities were found at the weld portion. The tendency for the formation of solidification cracking and weld porosities decreased with increased welding current.

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The influences of age hardening and HIP (Hot Isostatic Pressing) on the mechanical properties of A356 (Al 7Si 0.6 Mg) casting alloys were studied. Cast bars were homogenized, heated and maintained at a temperature of 540°C for a duration of 2 hours, followed by rapid cooling in a polymeric solution. The castings were age hardened at 180°C for a duration of 4 hours before being subjected to HIP process at pressure of 104 MPa for 2 hours. The results indicated that the age hardening process used improved the tensile properties of A356. The HIP process removed the internal surface-connected porosities and improved the ductility of the samples significantly. Additionally, HIP reduced scattering in the tensile test data

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In this study, porous titanium composites containing 5, 10 and 15 wt. % nanobioglass were fabricated by space holder sintering process. The pore morphology and phase constituents of the porous samples were characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The mechanical properties were determined by compression test. The porosity of the sintered samples showed an upward trend with an increase in bioglass content. As the bioglass content was increased, the compressive strength was first increased and then decreased. The results obtained in this work suggest that the fabricated porous compact with 10 wt. % bioglass with compressive strength value of about 76.7 MPa, high porosity and good biocompatibility has the potential application for bone tissue engineering.