Effects of Different Ageing Processes on Microstructure and Mechanical Properties of 6063 Aluminum Alloy

Single step ageing (180 ℃×6 h) and double step ageing (170 ℃×2 h+200 ℃×1.5 h) for 6063 aluminum alloy were carried out, and effects of different ageing processes on microstructure and mechanical properties were studied. The results show that hardness, tensile strength, yield strength and elongation of double step aged alloy were better than that of single step aged alloy. There were metastable β″ phases in transgranular and spheroidized precipitated phases at crystal boundaries, what′s more, an obvious precipitate-free-zone (PFZ) existed around grains boundary. After double step ageing, the β″ phase in transgranular was smaller, and precipitated phases at grain boundaries distributed discontinuouslies and PFZ was narrow.