THE EFFECT OF PUNCH SPEED ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF EXTRUDED A356-SIC COMPOSITES

The presence of porosity-particle clusters as well as gas and shrinkage pores in the cast Al-SiC composites can be regarded as influential factors that deteriorate the particle-matrix interface, and hence the mechanical properties of such composites. The thermo mechanical processing of these composites results in the reduction of porosity content as well as improvement in the particle-matrix interface. In the present study A356-SiC composites containing 10Vol% of SiC particles (38µm in size) were produced by compo casting method, and subjected to hot extrusion with various punch speeds in the range of 1-5 mm/s. It was concluded that the extruded samples exhibited more homogeneous particle distribution, lower porosity content and improved mechanical properties when compared with as-cast specimens. The increased punch speed resulted in the deterioration in the particle distribution, more fractured particles, and increase of porosity and hence decrease of mechanical properties such as UTS, Young modules and Elongation. However, the yield strength increases by increasing the punch speed.