Influence of Post Processing and Alloying with Zn on Formability of an Mg-2Al-0.5Ca-0.4Mn Alloy

Single-pass differential speed rolling (DSR) is an effective route for strengthening magnesium alloys through grain refinement induced by dynamic recrystallization (DRX); however, the accompanying strong basal texture often limits ductility and formability. In previous work, an Mg-2Al-0.5Ca-0.4Mn alloy (namely AXM20504) in the T4 condition was subjected to single-pass DSR with thickness reductions of 20% and 40% with a preheat temperature of 400 °C and a roll temperature of 300 °C, followed by post-annealing at 350-450 °C for durations of 20-60 min to systematically investigate static recrystallization (SRX), texture evolution, and mechanical response. Electron backscatter diffraction (EBSD) revealed that post-annealing promoted progressive SRX, with nearly complete recrystallization achieved at 450 °C for 40 min. This transition was accompanied by substantial basal texture weakening, reduced kernel average misorientation (KAM), and significantly lower grain orientation spread (GOS), indicating effective stress relief and formation of strain-free grains. As a result, tensile ductility increased from ~5% in the 40% as-rolled condition to ~12% after optimized post-annealing, while ultimate tensile strengths were retained above 200 MPa, much higher than the initial T4 strength. While these findings demonstrate that post-annealing is a critical step in restoring ductility and enhancing the formability of DSR-processed Mg alloys, certain types of alloying can also assist in a favorable balance between strength and formability for sheet forming applications. Alloying with Zn has been shown to improve ductility to a higher than 20% elongation at break as compared to 5% for the T4 AXM base material, showing that processing techniques and alloying have a high impact on the formability of Mg-based alloys. The zinc-based alloys in this study include Mg-2Al-0.5Ca-0.4Mn-0.5Zn (namely AXMZ2050405) and Mg-2Al-0.5Ca-0.4Mn-1Zn (namely AXMZ205041), both of which demonstrated improvements in mechanical properties as compared to the base alloy, AXM20504.