Heat Treatment of High-Pressure Die Castings

High-pressure die-cast Al alloys cannot normally be heated at high temperatures due to the presence of pores containing entrapped gases, which lead to the formation of surface blisters. It has been found that blistering can be avoided by using considerably 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.[1–3] For T6 tempers, increases in 0.2 pct proof stress of 80 pct for 360 and 115 pct for 380 have been obtained compared with as-cast values. Using a T4 temper, ductility is improved without any sacrifice in strength.