Evaluation of the Microstructure and Properties of As-Cast Magnesium Alloys with 9% Al and 9% Zn Additions

The need to reduce energy consumption means that it is necessary to reduce the weight of vehicles. However, a thick wall of massive elements promotes the formation of casting defects, which must be removed by either plastic processing (straightening) or welding methods (surface and internal discontinuities). Basic alloys contain Al and Zn as the main alloying elements. The studies involved an evaluation of the microstructure and properties of alloys at ambient and elevated temperatures. The microstructure observation revealed a dendritic structure with the presence of low-melting eutectic, and intermetallic and Laves phases in the interdendritic areas. The presence of these phases may pose significant limitations during welding work. Thermal conductivity coefficient measurements showed that it is constant at temperatures up to 200 °C and is 49 W/mK for 9% Al and 77 W/mK for 9% Zn. The tensile test reveal that the most favorable tensile strength (120 MPa) occurs at temperatures of 150 °C for the 9% Zn alloy and at 180 °C for the 9% Al alloy.