Construction of Phase Diagrams of Mg-Zn with Selected Rare Earth (R.E) Elements

Abstract

Rare earth alloys are a relatively new group of materials. Magnesium is the lightest structural metal, which is used in a variety of markets and applications, each one using the unique physical and mechanical properties of the element and its alloys. Addition of RE can refine the grains and weaken the anisotropy to improve its ductility and produce thermally stable precipitates with high melting point (above 620 °C), an improvement over precipitates of the Mg-Zn system. The high temperature strength and creep resistance of Mg alloys, such as ZK60, which is Mg alloyed with other elements often aluminum, zinc, manganese, silicon, copper, rare earths and zirconium, are improved by the addition of various amounts of rare earth elements (i.e. 0.5, 1.5, and 2.5 wt%). The Phase Diagrams and thermodynamic properties of these alloys are necessary for the modeling and development of materials and processes for innovative applications involving rare-earth based materials. However, there are very few known phase diagrams of Mg and magnesium alloys with rare earth elements. In this work we study the construction of the phase diagram of Mg-Zn alloyed with Pr, a light R.E. element, Y, and Er, a heavy R.E. element respectively using the Thermo-Calc [1] commercial software.