退孪生行为以及{1012}孪晶片层结构对镁合金力学性能的影响

EFFECTS OF UNTWINNING AND {10(?)2} TWIN LAMELLAR STRUCTURE ON THE MECHANICAL PROPERTIES OF Mg ALLOY

为了引入不同含量的{1012}孪晶,沿热轧退火态AZ31镁合金的轧制方向进行变形量分别为1%,3%和5%的动态塑性变形,并对预变形材料进行退火去应力处理.沿预变形镁合金不同的方向进行拉伸实验,分别研究分析了不同的变形量下退孪生行为和{1012}孪晶片层结构对材料力学性能的影响.研究结果表明:沿预变形方向拉伸时,退孪生发生,并且明显地改善了最大流变应力.{1012}孪晶体积分数越大,屈服强度和最大流变应力越高,这说明由退孪生导致的织构强化作用在改善镁合金的力学性能方面起到了重要的作用;沿初始横向拉伸时,位错滑移主导变形,预变形材料的力学性能并无太大提高,说明{1012}孪晶片层的分割导致的晶粒"细化"对镁合金力学性能的影响并不明显.

Strengthening mechanism related to （1012） twinning plays an important role in improving mechanical properties of Mg alloy. In this work, a hot-rolled AZ31 Mg alloy sheets were subjected to dynamic plastic deformation （DPD） along the rolling direction and tests were inter- rupted at strains of 1%, 3% and 5% with the aim of introducing {101^-2} twins, and then were annealed at 200 ℃ for 3 h to eliminate the dislocations. The tensile deformation behavior and the microstructural evolution of these pre-deformed samples containing {101^-2} twin lamellar structure with the aim of analyzing effects of untwinning and {101^-2} twin lamellar structure on the mechanical properties of materials were investigated. When subsequent tensile deformation is carried out along the DPD direction, untwinning causes a significant increase in the maximum flow stress. And the tensile yield stress and the maximum flow stress increases significantly with the volume fraction of twins. The texture hardening which is caused by the texture change attributable to untwinning plays an important role in improving mechanical properties of materials. When ten- sion is carried out along the initial transverse direction, slip dominated plastic deformation and {101^-2} twinning activity is restrained. The tensile yield stress increases slightly with pre-strain,suggesting that the hardening contribution of initial grain refinement by {101^-2} twin lamellae is not very significant during deformation.