Constitutive Models for the Description of Creep and Plasticity of Cast and Wrought Mg-Al and Mg-Zn Alloys

Investigations on the microstructural aspects of creep in Mg-Al alloys resulted in the development of a constitutive model, describing the strain rate dependence on applied stress and temperature. The model was used to describe the behaviour of the single-phase AZ31 alloy, as well as of the more complex materials. These analyses demonstrated that the behaviour of hcp Mg-Al alloys follows, in general terms, the same well known scheme typical of fcc Al-Mg alloys, also in respect to the existence of two regimes, the first characterized by an n= 3 stress exponent, and the second described by the modified form of the Garofalo equation. A low stress regime dominated by grain boundary sliding was also observed in fine-grained alloys. A similar approach was used to analyse creep and plasticity of Mg-Zn alloys.