对双峰织构类型AZ31镁合金板材力学性能各向异性的分析

目的 制备双峰织构类型的AZ31镁合金板，以改善板材微观组织和弱化基面织构，研究微观组织对力学性能各向异性的影响规律，以提高镁合金板材的成形性能。方法 通过弯曲限宽矫直技术对0°、30°和60°轧向切样的板材进行热加工以预制拉伸孪晶，获得双峰织构类型的AZ31镁合金板材，通过EBSD获取板材的微观组织。对RD、45°和TD方向的原始板材进行室温单向拉伸实验，获得板材的工程应力-应变曲线及力学性能参数，并计算r值(塑性应变比)与n值(应变硬化指数)。结果 弯曲限宽矫直技术可诱发大量拉伸孪晶形成ED偏转织构，将偏转织构与基面织构共存的板材称为双峰织构类型AZ31镁合金板材。拉伸孪晶的出现显著细化了晶粒，弱化了基面织构强度，使板材的屈服强度下降，极大提升了材料塑性。其中30°轧向切样的板材ND面塑性力学性能各向异性的改善效果最好，其r值最小、n值最大。结论 双峰织构类型能够弱化AZ31镁合金板材基面的织构强度，提高材料塑性。拉伸孪晶含量越高，板材的强度与塑性越好，力学性能各向异性的改善效果也越显著。

Analysis on Anisotropy of Mechanical Properties of Bimodal Texture Type AZ31 Magnesium Alloy Plate

The work aims to prepare a bimodal texture type AZ31 magnesium alloy plate to enhance the plate microstructure and reduce the substrate texture, thereby investigating the effect of microstructure on the anisotropy of mechanical properties and improving the formability of magnesium alloy plate. The plate rolled to 0°, 30° and 60° with rolled cut sample was hot processed by bending limit width straightening technology to prefabricate the stretch twin, the AZ31 magnesium alloy plate of bimodal texture type was obtained, and the microstructure of the plate was obtained by EBSD. The original plate in the RD, 45°and TD directions was subject to unidirectional tensile experiment at room temperature, and the engineering stress-strain curve and mechanical property parameters of the plate were obtained, and the r value (plastic-strain ratio) and n value (strain hardening index) were calculated. The bending limit width straightening technology could induce a large number of stretch twins to form ED deflection texture, and the plate where the deflected texture and the base texture coexist was called bimodal texture type AZ31 magnesium alloy plate. The appearance of stretch twins significantly refined the grains, weakened the texture strength of the substrate, reduced the yield strength of the plate, and greatly improved the plasticity of the material. Among them, the improvement effect of the anisotropy of the plastic mechanical properties of ND surface of the plate with 30° rolled cut sample was the best, and its r value was the smallest and the n value was the largest. The bimodal texture type can weaken the strength of the basal texture of AZ31 magnesium alloy plate and improve material ductility. The higher the twinning content, the better the strength and plasticity of the plate, and the more significant the improvement in mechanical anisotropy.