Evolution of precipitates of Al-Cu alloy during equal-channel angular pressing at room temperature

The evolution of precipitates and hardness changes in Al-Cu alloys during equal-channel angular pressing(ECAP) at room temperature were investigated by hardness measurement, X-ray diffraction analysis and transmission electron microscopy. The results show that with the increase of the total equivalent strain during ECAP from 0 to 8.4, the hardness of specimens with metastable theta phase increases first and decreases in later period. The hardness increases Successively in specimens containing metastable theta' phase and equilibrium theta phase. It is believed that the evolutions of hardness are related to the mechanism of re-dissolution of precipitates. A critical nuclei size concept is provided to express the mechanism Of Such re-dissolution of three precipitates in Al-Cu alloys.