Effect of severe plastic deformation process on microstructure and mechanical properties ofAlSi/SiC composite

Abstract

AlSi11 matrix composites reinforced with SiC particles have been fabricated by high pressure die casting assisted by ultrasonic mixing. Severe plastic deformation process was performed on the as cast AlSi/2wt.%SiC composite using the modified channel with the twisted output (TCAP) at three temperatures of 350, 400 and 450 °C. The TCAP tool consists of helical part in the horizontal area of the channel allowing for simulation of back pressure and thus resulted in the increase of extrusion force and local plastic deformation. The most important issue of the presented investigations was to refine dendritic cast microstructure of the prepared composite during one pass of TCAP. As a result, a composite with a matrix containing equiaxed α(Al) grains of few microns depending on TCAP temperature and β(Si) particles of about 1 μm in size with twinned structure was produced. The dynamic recrystallization process during TCAP at 450 °C manifested by the grain growth of α(Al) and decrease of dislocation density was observed to affect the sample hardness causing its decrease. The mechanical properties of the composite extruded by TCAP were measured by compression testes and the maximum plastic deformation of about 35% and the compressive strength near 300 MPa were observed. These values were similar for all samples extruded at temperatures between 350 and 450 °C and generally are better comparing with AK11 alloy subjected to different plastic deformation processes.