Development of heat resistant magnesium alloys for automotive powertrain parts

Rare earth elements (RE) of 1 to 3mass% in the form of mischmetal are added to Mg-Al-Zn-Ca alloys in order to improve their heat resistance. Furthermore, Zn content was varied in order to suppress hot tearing that occurs during diecasting. Increase in RE content leads to increase in the amount of acicular Al-RE compound, resulting in improvement of heat resistance. Addition of large amount of Zinc to the alloys results in the formation of an intermetallic compound that crystallizes at low temperature, and consequently, fluidity is improved, but hot tearing occurs during diecasting of products with a complex shape. One of the alloys designed from the above results, Mg-0.5%Zn-6%Al-1%Ca-3%RE, has good diecastability and comparable heat resistance with the conventional aluminum alloy, ADC12, used for diecasting of automotive powertrain parts.