Study on hot deformation behavior and workability of squeeze-cast 20 vol% SiCw/6061Al composites using processing map

The hot deformation behavior and workability of squeeze-cast 20 vol%SiCw/6061Al composites were investigated by isothermal compression test and development of processing map, which was verified by uniaxial upsetting and two-directional forging of big cylindrical billets. Due to dispersed strengthening caused by SiC whiskers, the activation energy of 20 vol%SiCw/6061Al composites was much higher than the self-diffusion activation energy of pure Al. Both the DMM and MDMM were reliable in predicting the safe deformation regions. The instability regions predicted by the Prasad's and Murty's instability criterion were smaller than the actual ones, while the Gegel's instability criterion was not appropriate in predicting the instability regions of 20 vol% SiCw/6061Al composites. The optimum deformation region was at higher temperature of 450-500 degrees C and higher strain rate of 0.1-1 s(-1), in which the compressed samples exhibited perfect surface without cracks and microstructure with few of cavities due to the occurrence of partial melting and dynamic recrystallization. With the increase of deformation temperature and strain rate, the deformation mechanism changed from dynamic recovery to dynamic recrystallization. Squeezing casting technique with high filtration pressure may also contribute to the increase of strain rate of DRX, which was helpful for hot forging of Al matrix composites with high productivity.