轧制温度对AZ31镁合金轧制板材中的{1011}-{1012}双孪生行为的影响

在150-350℃温区内不同温度下轧制AZ31镁合金板,观察了不同温度下轧制变形量为9%的AZ31镁合金板材的显微组织,研究分析了轧制温度对轧制板材中{1011}-{1012}双孪晶的含量、类型以及高温轧制过程中双孪晶中的动态再结晶行为的影响,讨论了板材中的孪晶对其力学性能的影响.研究结果表明:在150-300℃温区内轧制时,板材组织中均有含量不等的{1011}-{1012}双孪晶,随着轧制温度的升高,孪晶含量下降.250℃以上轧制的板材中单片一次孪晶中出现的双孪晶类型较为单一,仅出现共面型双孪晶.在250℃以上轧制板材中的双孪晶晶界处中可以观察到明显的动态再结晶现象,这些动态再结晶晶粒对孪晶界和孪晶起到消除和吞噬的作用.350℃下轧制的AZ31镁合金板材中未观察到{1011}-{1012}双孪晶.随着轧制温度的升高,镁合金轧制板材的强度减弱而塑性增强.

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

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.