Compressive plastic deformation of an AS21X magnesium alloy produced by high pressure die casting at elevated temperatures

The hot deformation behaviour of an Mg–Al–Si–RE (RE=rare earth) alloy produced by high pressure die casting has been investigated by means of compression tests in the temperature and strain rate ranges of 125–300 °C and 10−5to10−1 s−1. The samples were deformed in the high pressure die casting state or after an exposure at 415 °C for 2 h (solution temperature) to evaluate any different response to deformation. A premature fracture at 45° with respect to the compression axis was observed in samples strained at low temperatures and high strain rates. The stress–strain curves exhibit the trend typical of materials in which deformation is recovery-controlled in the high Z regime (Z is the Zener–Hollomon parameter), while at low strain rates and high T, the flow curves exhibit a softening typical of recrystallisation phenomena. Constitutive parameters were evaluated in order to understand the microstructure better. Light microscopy analysis has been performed to correlate the microstructure to the deformation parameters in all the tested conditions. Microstructural investigations indicate the presence of recovery mechanisms at high Z and recrystallisation during deformation in the low strain rate-high temperature regime.