In this paper, the rolling textures of six magnesium alloys containing different levels of zinc and rare earth (e.g., mischmetal or Y) additions are examined. The overall texture strength and the basal pole intensity aligned with the sheet normal direction is lower for rare earth containing alloys than for conventional alloys. The distinct textures generated in this study allow investigation of the influence of texture on the mechanical response. The anisotropy of the yield and flow strengths is reversed and the planar anisotropy is reduced (r ~ 1) in comparison to conventional alloys. Both aspects of the anisotropy are related to the fact that the dominant texture components in the Mg-Zn-RE alloys place more grains in favourable orientations for basal slip and tensile twinning, particularly during transverse direction tension. Mg sheets with lower r-value promise to have improved forming behaviour, at least under straining conditions which call for thinning of the sheet.

No abstract

No abstract

Although conventional Mg alloys develop strong crystallographic textures during deformation that persist during annealing, the addition of rare earth (RE) elements can induce comparably weaker textures. The texture weakening effect is explored using hot-rolled Mg-Y alloys of a single phase to focus on the possibility of solute effects. Of the studied compositions, the richer alloys ( ‡0.17 at. pct) show the weakening effect, whereas the most dilute alloy (£0.03 at. pct) does not. Electron backscattered diffraction (EBSD) analysis of intragranular misorientation axes (IGMA) indicate that the geometrically necessary dislocation (GND) content in dilute, hotrolled alloys contain primarily basal hai dislocations. At higher concentrations, the dislocations are predominantly prismatic hai type. This change in the GND content suggests a change in dynamic recrystallization (DRX) mode. For example, nonbasal cross slip has been associated with continuous DRX. Furthermore, nonbasal slip might also promote more homogenous shear banding/twinning. Both of these mechanisms have been shown previously to give rise to more randomly oriented nuclei during DRX. Energy dispersive X-ray spectroscopy performed through transmission electron microscopy shows that Mg-Y exhibits significant grain boundary solute segregation, consistent with recent observations of solute clustering. Slow grain growth may be explained by solute drag. It is hypothesized that limited grain boundary mobility suppresses conventional discontinuous DRX, which has been shown to retain the deformation texture. The promotion of nonbasal slip and suppression of grain boundary mobility are proposed as solid solution-based mechanisms responsible for the observed texture weakening phenomenon in Mg rare earth alloys.

No abstract

No abstract

The influence of the initial microstructure on the deep drawability and the associated microstructural evolution in two different magnesium alloy sheets, AZ31 and ZE10, has been examined. Tensile testing at room temperature shows that the AZ31 sheet has high plastic strain ratios, r = 2 ~ 3, which are caused by strong basal-type texture. The ZE10 sheet shows lower r values, r ~ 1, as a result of its weak texture. Deep drawing experiments carried out over the temperature range 100-300 °C revealed that the ZE10 sheet can be successfully deep drawn at lower temperatures than AZ31 sheet. The ZE10 cups show earing despite the weak texture and low normal anisotropy, while earing of the AZ31 cups is negligible. In the ZE10 cups, deformation is accommodated mainly by slips and by compression as well as secondary twinning. The occurrence of dynamic recrystallisation is observed in successfully deep-drawn AZ31 cups.

No abstract