Effects of high-pressure heat treatment on the solid-state phase transformation and microstructures of Cu61.13Zn33.94Al4.93 alloys.

The phase transformation activation energy of the Cu61.13Zn33.94Al 4.93 alloys, which were treated at 4 GPa and 700 degC for 15 minutes, was calculated by means of differential scanning calorimetry curves obtained at various heating and cooling rates. Then, the effects of high-pressure heat treatments on the solid-state phase transformation and the microstructures of Cu61.13Zn33.94Al4.93 alloys were investigated. The results show that high-pressure heat treatments can refine the grains and can change the preferred orientation from (111) to (200) of a phase. Compared with the as-cast alloy, the sample with high-pressure heat treatment has finer grains, lower b' - b and b - b' transformation temperature and activation energy. Furthermore, we found that high cooling rate favours the formation of fine needle-like a phase in the range of 5-20 degC/min. [ABSTRACT FROM AUTHOR]