Influence of microstructure and inhomogeneity on the properties of the pressure die cast magnesium alloy AM50 HP.

The paper deals with the influence of microstructure and manufacture induced porosity on the mechanical properties of plate-like components from the pressure die cast alloy AM50 HP. The assessment of the material behaviour was based upon microstructural investigations by means of light and electron scanning microscopy, hardness measurements, tensile tests, in-situ tensile and in-situ bending tests. The results showed a coarsening of the grain and dendrite structure, respectively, and an increased percentage of porosity from the rim to the middle of the plate. In addition, the matrix grains had a cored structure. Hence is followed an irregular microhardness course through the plate thickness and the reduction of the microhardness values from rim to the middle of the plate. Tensile and in-situ tensile tests on specimens, which due to the different cutting from the plate obtained more pores, resulted in reduced strength values, but especially in decreased total elongations. Specimens, in-situ tested at a temperature >120 degrees centigrade led to lower values of strength and elongation. The effect of the porosity on the values of the in-situ bending test was not so serious.