Development of lightweight, creep resistant Mg–Zn–Al alloys for automotive applications: Influence of micro-additions of quaternary elements

Magnesium alloys are preferred for applications requiring lightweight, high specific strength, and stiffness since magnesium is the lightest of all structural metals with a density of 1.74 g/cm³. Because of the significant weight reduction, the usage of magnesium-based alloys in various aviation and automobile components will result in low fuel/energy consumption and gas emissions. In addition to weight reduction, some automobile components, such as the transmission case and engine block components, also need to be creep-resistant and maintain their mechanical strength at high temperatures (over 100 °C). Due to proper Zn/Al ratio control, significant reduction, or elimination of the thermally unstable Mg₁₇Al₁₂ from the phase composition, Mg–Zn–Al (ZA) alloys are designed to demonstrate creep resistance and high-temperature mechanical capabilities. The development of lightweight ternary Mg–Zn–Al (ZA) alloys with characteristics suited for use in high-temperature automobile components was reviewed in this work. The addition of some quaternary elements to previously developed ZA alloys has shown excellent potential in phase refinement, inhibition of Mg₁₇Al₁₂ intermetallic phase formation, excellent heat resistance, and increased yield strength at high temperatures. This is due to the formation of thermally stable phases and the inhibition of dislocation and grain boundary sliding. The review further emphasized relevant quaternary elements and processing techniques which resulted in improved structure, creep performance, and other high-temperature mechanical properties of ZA alloys.