Microstructure and mechanical properties of the pressure die cast magnesium alloy AZ91D after long-term thermal exposure

摘要

The thermal resistance of the pressure die cast magnesium alloy AZ91D is yet not investigated sufficiently. Inorder to assess the effect of a thermal exposure on the microstructural stability and the mechanical properties, the alloyAZ91D is subjected to a long-term annealing for 1 000 h at 80 °C, 100 °C, 120 °C, 150 °C, 180 °C and 200 °C. After theannealing, the microstructural appearance of the material is investigated by light and scanning electron microscopy andcompared with the as-cast condition. Furthermore, tensile tests, hardness measurements and fracture toughness tests arecarried out and the measured values are discussed on the basis of the microstructural changes. The results reveal thedistinct correlation between the microstructural changes, especially the precipitation of discontinuous and continuousβ-particles (Mg17 Al12), and the mechanical properties.