Effect of alloying elements on heat treatment response of aluminium high pressure die castings

High pressure die cast (HPDC) aluminium components that respond to age hardening cannot normally be solution treated at high temperatures because the presence of internal porosity and entrapped gases leads to the formation of surface blisters. Parts may also become dimensionally unstable due to swelling. These factors that prevent heat treatment present significant limitations to the utilisation of HPDC components. Now it has been found that blistering and dimensional change can be avoided by using much shorter solution treatment times and lower temperatures. Experiments with alloys 360 (Al-9•5Si-0•5Mg) and 380 (Al-8•5Si-3•5Cu) have shown that strong responses to age hardening are still possible following these modified solution treatments. In the current paper, the role of critical alloying elements is considered in both current specification Al-Si-Cu-(X) alloys, and also in newly developed alloy compositions. It is shown that 0•2% proof strengths over 400 MPa may be readily achieved by heat treating conventionally produced die castings. © 2010 Maney Publishing.