Particulate refinement and redistribution during the axisymmetric compression of an Al/SiCp metal matrix composite

Previous investigations have shown that the thermomechanical processing of Al/SiC_p metal matrix composites (MMC) can reduce the size of SiC particles and yield a more homogeneous spatial distribution of particles. Both of the above microstructural features are conducive to improvements in the ductility and fracture toughness of MMC. This research was designed to measure the effectiveness of thermomechanical processing on the microstructure of an MMC by monitoring the change in SiC particle size and spatial distribution during the course of deformation processing. The MMC used in this investigation was the Al alloy 2618 reinforced with 14 vol% SiC_p. Continuous and discontinuous axisymmetric compression tests were conducted, both at room and elevated temperatures. Optical and quantitative microstructural analysis was performed over many fields from each as-deformed specimen. This study finds that at elevated temperatures, a large number of fractured SiC particles corresponded with the macroscopic peak flow stress of the composite. Furthermore, the propensity for particulate fracture was most pronounced when specimens were deformed at room temperature, diminishing somewhat when specimens were deformed at elevated temperatures. However, deformation at elevated temperatures resulted in a more uniform spatial distribution of SiC particles within the matrix.