The effect of grain size distribution on the shape of flow stress curves of Mg-3Al-1Zn under uniaxial compression

To investigate the effect of initial microstructure on the evolution of flow stress curves during plastic deformation, cylindrical specimens of two types of AZ31 Mg alloy with different grain size distributions were compressed in the rolling (RD) and normal directions (ND) at 300 °C. For specimens with a compression axis parallel to the RD, an AZ31 Mg alloy that had an inhomogeneous and coarse distribution of grain size exhibited more distinct twin-dominated plastic deformation and sigmoidal shape of the flow stress curve at higher strain rates. The AZ31 alloy having larger grain size showed more favorable for twin-dominated deformation at a given temperature and strain rate. The specimen deformed at a higher strain rate only exhibits twin-dominated deformation and has a large area fraction of grains deformed by propagation of twin bands (TB) through its parent grains (PG).