Study on edge cracking and texture evolution during 150 °C rolling of magnesium alloys: The effects of axial ratio and grain size

Pure Mg, AZ31 (Mg–3 wt%Al–1 wt%Zn) and experimental alloys, Mg–1 wt%Zn–1 wt%In, Mg–2 wt%Li–1 wt%Zn, Mg–2 wt%Li–1 wt%Zn–1 wt%In were rolled at 150 °C to 0.3 and 0.55 strain. The samples rolled to 0.3 strain were subsequently annealed for 10 min at 400 °C. The texture was evaluated in rolled and in rolled/annealed conditions. The axial ratio (c/a) of the alloys strongly influenced edge cracking during rolling (expressed as cracking index, IC), which was explained via the influence of c/a on the twinning mode. The as-cast grain size did not correlate to IC (edge cracking). Texture intensity was strongly influenced by the as-cast grain size (which was attributed to plastic compatibility at grain boundaries), showed weak correlation to the lattice parameter a, but did not depend on c/a. The Mg–2 wt%Li–1 wt%Zn alloy, with fine grain size and small c/a and a, exhibited the optimum combination of weak texture and crack-free rolling at 150 °C.

► In Mg alloys with Li, Zn, In and AZ31 rolled (150 °C) & annealed, edge cracking depends on the twinning mode governed by the axial ratio.
► AZ31 shows tensile twinning & extensive edge cracking, Li-containing alloys double twin and do not edge crack.
► Texture intensity depends on the initial grain size, due to grain boundary plastic compatibility.
► Texture intensity correlates with the lattice parameter a.
► Mg–2Li–1Zn shows the optimum combination of weak texture and low cracking.