The Potential for use of Heat Treated Aluminum High Pressure Die-Castings in Engine Applications

Aluminum alloys used for most high pressure die-castings manufactured worldwide are based on the Al-Si-Cu-(Fe) system, examples being the alloys (AA)380, (JIS) ADC10, (JIS) ADC12, and EN-AC-AlSi8Cu3(Fe). These alloys are used for a wide range of applications including engines and drivetrains for which they are usually heat treated to a stabilized T5 temper. Such a treatment does not, however, provide a significant improvement to the as-cast mechanical properties.

The reason why conventionally produced HPDC components are not heat treated to the higher strength T6 or T7 tempers is that a standard solution treatment cycle (e.g. 8h at 540°C) causes internal pores to expand resulting in unacceptable surface blistering and dimensional instability. Recently a modified heat treatment regime has been developed which avoids these problems and allows large improvements (e.g. around 100%) to be achieved in some tensile properties. Fatigue resistance and thermal conductivity are also improved. The potential for using age hardened, high pressure diecast alloys for engine and drivetrain applications can now be evaluated in light of this discovery. In the current paper, a summary of results to date are presented, and brief consideration is given to possible changes in the design of future engine and drivetrain components.