Microstructural evolution of Mg–Al–Ca–Sr alloy during creep

To provide new insight into microstructural development during creep, sequential EBSD (electron backscatter diffraction) orientation maps were obtained from fixed surface areas at intervals in creep tests of a high-pressure die-cast Mg–8.5Al–1Ca–0.3Sr alloy. Samples were tested at 200 °C at various stress levels to achieve power-law creep behavior. In all specimens, steady-state creep was marked by the formation of tension twins. At intermediate stress levels, specimen failure was initiated by the formation of defects at boundaries with high crystallographic misorientation. However, at high stress levels, the failure mechanism was assisted by the crack formation at interdendritic boundaries with low crystallographic misorientation.