Microstructural refinement and wear property of Al-Si-Cu composite subjected to extrusion and high-pressure torsion

Abstract

The effect of high-pressure torsion (HPT) on the microstructure and the mechanical properties, especially the wear properties, of an Al-Si-Cu alloy (represented by Al-15%Si-2.5%Cu-0.5%Mg) and its composite, which was reinforced by SiC particles (SiCp) at a volume fraction of 5%, was investigated systematically in this study. The Al-Si-Cu/SiCp composite is produced in a powder metallurgy process followed by hot extrusion (EXTR) at 565°C. The EXTR specimen is also subjected to HPT processing at an anvil rotation speed of 0.5rpm under a quasi-hydrostatic pressure of 5GPa.HPT processing leads to a nanostructured microstructure comprised of equiaxed ?-Al grains (60-70nm) and secondary particles and phases; the SiCp with a damaged facet, the phase exhibiting high Mg content and the intermetallic CuAl2 phase, for the Al-Si-Cu/SiCp composite. The values of the tensile strengths and hardness of the HPT specimens are nearly twice higher than those of the EXTR specimens for the Al-Si-Cu alloy and the Al-Si-Cu/SiCp composite. Ball-on-disc tests were used to examine the wear resistance of the processed materials. The wear test results indicated that HPT processing significantly reduces the wear loss, thereby leading to improvement in the load bearing capacity and the wear resistance of the Al-Si-Cu alloy and the Al-Si-Cu/SiCp composite. This behavior is linked to HPT processing, based on the refined and homogenous microstructure that results in an increase in the hardness. © 2014 Elsevier B.V.