Design of Non-Heat Treatable High Pressure Die Casting Al Alloys: A Review

In recent years, Non-Heat Treatable High Pressure Die Casting Al alloys (NHT-HPDC Al alloys) have been proposed and developed for integrated die casting in the automotive industry. These alloys exhibit excellent castability and can achieve sufficient mechanical properties without the need for heat treatment. Despite their industrial significance, there is a lack of an updated and comprehensive description of such alloys. The insufficient availability of literature and the absence of a systematic design mentality have hindered their development. Therefore, this study reviews several aspects of NHT-HPDC Al alloys. Firstly, the NHT-HPDC Al alloys are divided into Al-Si, Al-Mg-Si and Al-Fe-Mg alloys, with the NHT-HPDC Al-Si alloys being the mainstream. The solidification behaviors of NHT-HPDC Al-Si-(Cu)-(Mg) alloys are discussed using phase diagram analyses. Secondly, the manipulation of critical phases is discussed, including: (i) impurity phase: Fe-rich phase (the neutralization treatment); (ii) strengthening phases: Eutectic Si phase (the modification treatment)/main alloying elements regulating phases/trace alloying elements regulating phases/ceramic particles. Thirdly, the typical three regions of NHT-HPDC Al-Si components and their formation mechanisms are identified and reviewed. Then, the influence of vacuum assistance and intensification pressure to the general quality of NHT-HPDC Al-Si components is comprehensively discussed. Finally, future challenges for NHT-HPDC Al-Si alloys are also proposed.