Microstructure and mechanical properties of severely deformed Mg-3%Al-1%Zn alloy via isothermal differential speed rolling at 453 K

The paper reported the microstructure evolution and mechanical properties of the severely deformed Mg-3%Al-1%Zn alloy sample via isothermal differential speed rolling (DSR) at 453 K. The present samples were subjected to DSR operations with the height reduction of 30% at the roll speed ratio of 1:3 for the lower and upper rolls, and these results were compared to those deformed by equal speed rolling (ESR). After two-pass of the DSR, most of the grains were refined markedly to ∼3.3 μm with a globular shape whose grain size was lower than that via ESR. In addition, Vickers microhardness values of the samples via DSR were higher than those via ESR. The results of tension tests revealed that yield and ultimate tensile strengths of the severely deformed samples via DSR were measured to be ∼198 and ∼228 MPa, respectively. It is worth noting that, with increasing numbers of operations, the tensile ductility of the sample deformed by the DSR was restored whilst the elongation of the sample deformed by the ESR was monotonously deteriorated although both of the cases exhibited lower elongation compared to the as-homogenized. Such phenomenon underlying the restoration of the tensile ductility was discussed by taking the role of the conjugated macro-shear deformation into account.