Effect of the final rolling speeds on the stretch formability of AZ31 alloy sheet rolled at a high temperature

The influence of final rolling speeds varying from 0.1 m/s to 0.4 m/s on the microstructures, textures, mechanical properties and stretch formability of AZ31 alloy sheets rolled at 550 degrees C was investigated in the present work. The results showed that in as-rolled condition, with increasing the final rolling speed, the grain size of the sheets increased whereas the basal texture intensity decreased. Twinning was still the main deformation behaviour even at high final rolling speed. After annealing, the sheets exhibited double-type textures with basal poles tilting at approximately from +/- 10 degrees to +/- 12 degrees in the rolling direction, and the basal texture weakened more remarkably via static recrystallization for the sheets rolled at higher final speed. By increasing the final rolling speeds from 0.1 m/s to 0.4 m/s, the Erichsen values of the annealed sheets at room temperature were enhanced from 4.9 mm to 6.3 mm resulted from the weakened basal texture, which leaded to a lower 0.2% proof stress, r-value, and a larger n-value. The main reasons for the twinning behaviour and weakened textures at high final rolling speeds were discussed. (C) 2015 Elsevier B.V. All rights reserved.