Effect of hot extrusion on microstructure and tribological behavior of Mg and Mg/SiC metal matrix composite produced by stir casting route

Magnesium based materials are the potential candidates to replace the conventional materials in automobile sector, so that the greenhouse gas emission from the automobiles can be reduced. But the use of magnesium based materials is very limited due to its low wear resistance and mechanical properties. The aim of this research work is to investigate the effect of hot extrusion on wear behavior of magnesium and magnesium/SiC composite develop by stir casting technique. Magnesium reinforced with 9% SiC (wt%) was fabricated by stir casting equipped with down pouring arrangement. Further pure Mg and Mg/SiC composite was subjected to hot extrusion at 400 degrees C with extrusion ratio 6:25 and extrusion speed of 1 mm s(-1). The dry sliding wear performance of pure Mg and Mg/SiC composite before and after extrusion was investigated at room temperature by using pin on disc type apparatus. Wear experiments were performed by using EN31 steel disk at constant speed with a load variation of 1 kg to 5 kg. The grain size was determined by using optical microscope images and worn surfaces were investigated by Scanning Electron Microscopy (SEM) equipped with Energy Dispersive Spectrometer (EDS). The optical images showed that the microstructures were significantly refined by extrusion. The wear resistance of extruded SiC composite was considerably enhanced and coefficient of friction much lower in comparison to as-cast magnesium and Mg/SiC composite as well as extruded pure magnesium. The results indicated that the extrusion process have a pivotal role in improving the wear resistance of the composite.