铸轧AZ31镁合金板温轧过程微观组织及裂纹研究

Study on Microstructure and Crack of Cast-rolled AZ31 Magnesium Alloy Sheet in Warm Rolling Process

研究了铸轧AZ31镁合金在125、175、225℃及单道次压下量10%和15%温轧工艺条件下板带金相组织、XRD和裂纹变化规律。结果表明低温轧制过程塑性变形主要是孪晶,变形带和剪切带,随变形量增加,粗大晶粒减小,条状孪晶增加;随温度升高,组织发生了部分再结晶,单道次变形量增加,晶格畸变加剧,再结晶晶粒增多;温轧后形成了典型基面织构（0002）,且强度峰值随温度升高和压下量增加明显增强;尽管动态再结晶对裂纹愈合有明显积极作用,但过大压下量和过快温降导致变形不均匀性增加和裂纹无法完全消除。压下量10%,轧制温度200~250℃有利于铸轧AZ31镁合金后续温轧过程塑性改善和裂纹愈合。

The microstructure, XRD and crack change rule of cast-rolled AZ31 magnesium alloy sheet at 125,175,225℃ and single pass reduction of 10% and 15% during warm rolling process were researched. The results show that plastic deformation is mainly twin, deformation band and shear band, coarse grain decreases and strip twin increases with the increase of deformation. Partial recrystallization is produced in the microstructure with the increase of temperature. When single pass deformation increases, the lattice distortion exacerbates and the recrystallization grains increase. The typical basal texture （0002） was formed after warm rolling, and strength peak value significantly enhances with temperature increment and the increment of reduction. Although the dynamic recrystallization has obvious positive effect on crack healing, too large reduction and fast temperature dropping cause the deformation heterogeneity increasing and the crack can not be completely eliminated. The reduction of 10% and rolling temperature 200-250＂C are beneficial to the plasticity improvement and crack healing of cast-rolled AZ31 Mg alloy in subsequent warm rolling process.