The influence of intergranular microstucture of Mg-Zn-RE alloys on properties at elevated temperatures

Two magnesium-alloys with small amounts of zinc and rare earths were invest igated in order to compare the influence of cast structure and heat treatme nt on hardness and tensile properties. The structure has been examined usin g the methods of scanning and electron microscopy; tensile tests were carri ed out at temperatures from ambient up to 300 degrees C, It was established that the structure of the alloys consists of fine equiaxial grains of soli d solution of Zn, and RE in Mg surrounded with a network of the ternary eut ectic of Mg-12(RE, Zn) or Mg12-xZnxRE type, which is hard and brittle, The eutectic is responsible for stability of mechanical properties of the alloy s at elevated temperatures up to 200 degrees C, They also reveal small resp onse to heat treatment, which make them cheaper to produce than other alloy s like ZE 41 or EZ 33 and suitable for High Pressure Die Casting (HPDC).