Hot deformation behavior of as-cast Mg-Zn-Mn-Ce alloy in compression

ZME200 (Mg-2.3Zn-0.4Mn-0.2Ce1) is a newly-developed magnesium sheet alloy for automobile closure and structure applications. The hot deformation behavior of as-cast ZME200 alloy was investigated by compression tests at temperatures (T) ranging from 250 to 450 °C and strain rates (ε̇) between 0.001 and 10 s−1. Most of the stress-strain curves exhibited typical dynamic recrystallization (DRX) behavior with a single peak stress followed by a gradual fall toward a steady-state stress. The flow behavior (hot working characteristics) can be described by the hyperbolic sine function, ε̇=A[sinh(ασ)]nexp(−Q/RT), where A, α, and n are material constants, σ is the applied stress, Q is the activation energy, R is the gas constant. Light metallography and electron backscattered diffraction (EBSD) were conducted to investigate the microstructure evolution under various deformation conditions. The results suggested that dynamic recrystallization was the main softening mechanism during the hot compression process. Both discontinuous and continuous DRX were the operating DRX mechanisms at temperatures between 300 °C and 450 °C. The former predominates mainly at low strains, while the latter dominates at moderate and higher strains. Twinning deformation and twin DRX were operative at relatively high strain rates of (1.0−10 s−1).