The effect of contraction twins and shear bands on the texture evolution during isothermal annealing and its effect on mechanical properties of AZ31 magnesium alloys

Cold-rolling and subsequent annealing were conducted on the commercial AZ31 hot-rolled plates with small (similar to 5 mu m) and large (similar to 50 mu m) grains. After cold-rolling, plenty of shear bands and contraction twins formed in the small grain sample (SG sample) and large grain sample (LG sample), respectively. During annealing, re crystallization firstly occurred in the shear bands and contraction twins due to the local strain concentration. The inclined basal texture with double poles in the cold-rolled SG sample transformed to a strong basal texture after annealing at 500 degrees C, while the strong basal texture in the cold-rolled LG sample was weakened by the twins related recrystallization. In compression test, the volume fraction of grains favoring for basal slip in the annealed LG sample was much higher than the annealed SG sample, this induced a lower yield strength and higher failure strain in the annealed LG sample. The texture variation also had great effect on the anisotropy and strain hardening behavior.