High temperature and strain-rate response of AA2124-SiC metal matrix composites

This paper presents the results of the study of the dynamic impact behaviour of the AA2124-SiC Metal Matrix Composite (MMC) material with different particle reinforcement sizes and qualities using a compressive Split-Hopkinson Pressure Bar (SHPB) apparatus. Mechanical tests were performed at strain rates 1000 s−1, 2000 s−1, and 3000 s−1 and at temperatures of room temperature (25 °C), 100 °C and 200 °C. Microstructural analyses were carried out on the samples pre and post-compression experiments to study the fracture characteristics and mechanisms of the MMC materials. The flow stress-strain, strain rate, temperature effects and deformation mechanism were investigated. The backscattered electron images show that a higher strain rate of deformation induces the formation of denser and smaller grain size of CuAl2 precipitates, especially in composites with smaller SiC particle sizes. Temperature has posed a minor effect on the microstructural change. Heating the samples close to a solution treatment temperature, and then followed by an air quenching has resulted in a fine dispersion of CuAl2 precipitates, as well as a high saturation for the materials with a higher volumetric fraction of SiC reinforcement. The SHPB compression results reveal that the 225XF material has developed the highest stress among all materials. For materials with a higher volumetric fraction of SiC reinforcement (225XE and 225XF), cracks and failures have appeared in the samples during high strain rate and high-temperature compression experiments, which is believed to be caused by the increased brittleness of the material as a result of intensified oxide phases.