Enhancing modulus and ductility of Mg/SiC composite through judicious selection of extrusion temperature and heat treatment

In the present study, a magnesium based composite with about 11-5 wt-%SiC particulates was synthesised using an innovative disintegrated melt deposition technique followed by extrusion at different temperatures of 350°C, 250°C, 150°C and 100°C. Microstructural characterisation of the extruded samples showed an increase in alignment of SiC particulates in the direction of extrusion, reduction in number of SiC particulate clusters and improved distribution of the SiC particulates as the extrusion temperature decreased. Good interfacial integrity and minimal porosity was also observed for all the samples. Mechanical properties characterisation revealed that a decrease in extrusion temperature from 350°C to 100°C led to a significant increase in hardness, elastic modulus, 0·2% yield strength while the average UTS and ductility remain unaffected. Subsequently, isothermal heat treatment at 100°C with holding times of 5 and 10 h were also carried out for samples that were extruded at 100°C. The results of tensile testing revealed that the heat treatment led to an approximately 3·6 times increase in ductility, did not affect the modulus. Considering the standard deviation, the 0·2% yield strength and UTS remained similar. An attempt is made in the present study to correlate the effect of decreasing the extrusion temperature as well as subsequent heat treatment with the microstructural and mechanical behaviour of the composite.