Hot deformation characteristics and mechanism of PM 8009Al/SiC particle reinforced composites

The hot deformation behavior of powder metallurgy-processed 8009Al alloys reinforced with 15% SiC particles (8009Al/SiCp composites) was investigated by compression testing at temperatures of 400-550 °C and strain rates of 0.001-1 s-1. The corresponding deformed microstructures were characterized by scanning and transmission electron microscopy. The results showed that the flow stress increased with increasing strain and then stabilized at a constant value after reaching a peak value. The stress level decreased with increasing deformation temperature and decreasing strain rate, which could be represented by a Zener-Hollomon parameter in the hyperbolic-sine equation that integrates strain, temperature and strain rate. The deformation activation energy for the 8009Al/SiCp composites was calculated to be 481-495 kJ/mol. The flow behavior of the composites was attributed to intense dynamic recovery caused by the high volume fraction of very fine Al12(Fe,V)3Si-phase dispersoids in the Al matrix. The accommodation ability between the SiC particles and the Al matrix was discussed as well.