Thermal Conductivity and Tensile Property of Mg-Zn-Y Casting Alloys with Long-Period Stacking Ordered Phase

Abstract

The Mg-Zn-Y alloy with long-period stacking ordered (LPSO) phase is known as attractive for automotive lightening engine components with strength at elevated temperature. On the other hand, it is considered that the thermal conductivity of magnesium alloys is lower than that of commercial aluminum alloys. Low thermal conductivity causes engine performance degradation. However, there is little study on the thermal conductivity of Mg-Zn-Y casting alloys. It is important study when we consider the application of high-temperature parts for engine components. Then we developed the Mg-Zn-Y casting alloys with strength at elevated temperature and good thermal conductivity. Our developed alloys have the fine LPSO phase with a net-like structure for higher strength and the pure magnesium matrix for better thermal conductivity. It is important that there is little or no solute element in the magnesium matrix for thermal conductivity. We accomplished these two good characteristics at the same time by optimizing the amount of zinc and yttrium contained in the Mg-Zn-Y casting alloys. Mg96Zn2Y2 die-casting alloy had a good thermal conductivity of over 100 Wm-1K-1 at 473 K. This was almost identical to the thermal conductivity of heat-resistant aluminum casting alloys for conventional engine components.