INFLUENCE OF ROLLING TEMPERATURE ON THE {1011}-{1012} TWINNING IN ROLLED AZ31 MAGNESIUM ALLOY SHEETS

Abstract

The most common manufacturing process for wrought magnesium alloy sheet is warm-rolling and the microstructure and properties of the product are strongly related with the rolling temperature.In particular,{1011} {1012} double twinning is an important supplemental mechanism for the deformation of magnesium alloys during rolling at low or moderate temperatures.Therefore, the present work studies the microstructural variation of magnesium alloy sheets AZ31 rolled to 9%at different temperatures in the range of 150—350℃,and discusses the influence of rolling temperature on the quantity and variety of {1011}-{1012} double twins,as well as recrystallization related to the double twins.The mechanical properties of the rolled sheets and the influences of twins on the mechanical properties have also been discussed.The results show that {1011}-{1012} double twins are observed in the sheets rolled at temperature ranging from 150 to 300℃.The fraction of double twin per unit area,and the number of variant types within each primary twin,decreases with the increasing rolling temperature.At the temperature above 250℃,only co-planar double twins are observed in each primary twin.Recrystallized grains are observed to nucleate at the twin boundaries in the sheets rolled above 250℃,these can consume the twin boundaries and resulting in merging of the twin grains.No {1011}-{1012} twins are found in the AZ31 magnesium alloy sheet rolled at 350℃.With the increase of rolling temperature,the yield strength decreases and the ductile elongation increase for the rolled magnesium alloy sheet.