Design of Secondary Alloy Compositions for High Performance Aluminium Pressure Diecastings

Abstract

High pressure die-casting (HPDC) is a widely used production technique for metal components that are required to have close dimensional tolerances and smooth surface finishes. Approximately 50% of the aluminium castings produced globally are manufactured by HPDC from secondary alloy and these are dominant in the automotive sector where they account for the majority of aluminium components present in each vehicle manufactured. Recently, it has been shown that industrially produced aluminium alloy high pressure diecastings (HPDC’s) can be successfully heat treated without encountering problems with surface blistering or dimensional instability. These processes may significantly improve the properties which develop from the alloys, thereby significantly increasing the scope of applications that may be realized. HPDC alloys however have not been developed specifically for heat treatment or the optimization of specific properties. In particular, recent work in Al-Si-Cu HPDC alloys has identified composition ranges of alloys for a) achieving yield strengths exceeding 400 MPa, b), rapid heat treatment that minimizes cost / cycle times, and c) high strength combined with elevated ductility levels. The role of alloying elements, composition limits and effects on mechanical property development are discussed.