Improved multiple ageing treatments for AA6111

The effects of multiple ageing treatments on the precipitation hardening response of aluminium alloy AA6111 has been studied by varying the first stage ageing temperature and period systematically. The effects of intermediate low temperature ageing dwell time were also studied. Throughout this work, the final ageing temperature was restricted to 180 degrees C in order to coincide with the temperature used for the paint-baking cycle in the industry. It is found that with proper multiple ageing treatments, the kinetics of the age hardening response can be reduced from 8 hours to 4 hours and that the peak hardness can be increased from 128HV to 132HV.