Deformation characteristics and recrystallization behavior of an AZ31 magnesium alloy subjected to high speed rolling

Magnesium AZ31 alloy sheets were rolled at 100 °C at three different speeds: (i) 1000 m/min (high speed rolling, HSR), (ii) 100 m/min (intermediate speed rolling, MSR) and (iii) 15 m/min (low speed rolling, LSR).High reductions of more than 70% were achieved in single pass by HSR and MSR, while the sheet fractured at a reduction of only 37% by LSR.During HSR and MSR, dynamic recrystallization (DRX) was observed at reductions of 37% and higher, which was the mechanism for the greater rollability; DRX is, in turn, related to the higher temperatures generated.Full recrystallization was achieved at reductions higher than 70% during MSR and HSR.The dominant DRX mechanism was twinning/shear banding induced DRX, which led to partially recrystallized and twinned microstructures at reductions from 37% to 58%.Thus, fine recrystallized grains formed along the shear bands, which possessed much higher number of twins and accommodated more dislocation slips.In regions outside shear bands, the twin density was much lower, continuous recrystallization can be seen in twin free regions as well as at twins.For a given reduction, the maximum intensity of the basal texture is weaker after HSR than after LSR, which is due to the activation of a larger number of contraction and secondary twinning and/or slip.The sheets were rolled at the high speed of 1000 m/min to six increasing reductions to generate a series of microstructures: (i) twinned and shear banded (8%-30%), (ii) partially DRXed and twinned (49%-58%) and (iii) fully DRXed (72%).These were annealed at temperatures from 200 °C to 500 °C for increasing time.As a comparison, the LSRed sheets were subjected to the same annealing conditions.Static recrystallization (SRX) kinetics were analyzed in terms of the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model and found to involve two sequential First and foremost, I would like to express my deepest gratitude to my supervisor, Professor Stephen Yue, for his guidance, patience and encouragement throughout my PhD project.Without his support, I would not have been able to pursue a great deal of my career endeavors and graduate experience.I would like to give special thanks to Prof. John J. Jonas for his helpful guidance and for imparting his profound knowledge of materials science to me.I am very grateful for his prompt response, perceptive advice and insightful discussion.I would like

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