Effect of SiCp reinforcement on high temperature deformation of SiCp/2124Al metal matrix composites

Abstract

In this study, the high temperature deformation behaviors of 2124Al alloy and silicon carbide particles(SiCp) reinforced Al matrix composites were investigated by means of hot compression test at temperature ranged 400~475℃ under strain rate ranged $10^{-3}-1s^{-1}$. Both materials were made by power metallurgy (PM) process route. The size of 2124Al and SiCp powers used as start materials in this study was 20 ㎛ and 8 ㎛ respectively. The billets of 2124Al and 5,10,20vol% SiCp/2124Al composites were fabricated by hot compression process under a pressure of 90MPa at 570℃ for 10 minutes. The stress-strain curves of SiCp/2124Al metal matrix composites during high temperature deformation exhibited a peak stress, and then the flow stress decreased gradually into a steady state with increasing the strain. The peak stresses for 2124Al alloy and SiCp/2124Al composite increased with decreasing the temperature and with increasing the strain rate. The dependence of flow stress on temperature and strain rate could be formulated well by a hyperbolic sine relationship using the Zener-Hollomon parameter. Using the normalized Zener-Hollomon parameter (Z/A), which is defined based on the load transfer theory, the effective flow stress on matrix of SiCp/2124Al composite is found to be similar to that of 2124Al alloy. Optical microscope (OM) and transmission electron microscope (TEM) were used to characterize the evolution of microstructure during the high temperature deformation. It was found that the flow-softening behavior was attributed to the dynamic recovery, local dynamic recrystallization and dynamic precipitation coarsening during the deformation of SiCp/2124Al composites. It was worth noting through the optical microstructure that the grain size in the SiCp rich region is smaller than that in the SiCp poor region, which indicated that the configuration of grain size was affected by the distribution of SiC particles. Quadrat method was used in this study in order to charac...