镁合金板材基面织构分布对称性调控及其对成形性的影响

Magnesium alloy sheet has a strong basal texture and thus its formability is poor. Through tailoring basal texture, the c axis of basal grains of magnesium alloy sheet will be tilted or be splitted as bimodal texture, causing the improvement of uni-axial formability. However, it is hard to meet the requirement of complex forming of the developing automobile parts. Therefore, aiming at seat frame of automobile, this project proposes a new idea to weaken the basal texture and improve its distribution along the ND direction using pre-deformation, further improve the formability of magnesium alloy sheet. Through analyzing the stress-strain characteristics of primary AZ31 sheet, studying the macro and micro evolution and mechanics model of tilting basal texture of the sheet during deformation, investigating the change mechanism of space location parameters of basal orientation with strain, quantity expression model of symmetry characteristics of distribution of basal texture, it is expected that the relation of the applied strain, micro mechanics, deformation mechanism, and distribution symmetry of basal orientation will be established, in order to obtain an excellent formable magnesium alloy sheet with suitable distribution symmetry of basal orientation. On this basis, by investigating the deformation foundation, deformation mechanic model will be established as well as deformation prototype technology of Mg parts, which will provide an important support for automobile parts’ application.

镁合金板材的基面织构很强，成形性差，现有织构调控可使镁合金基面c轴在一定程度上偏转或形成双峰织构，改善镁合金板材的单轴成形能力，但无法满足快速发展的汽车轻量化零部件的复杂成形要求。为此，本项目以汽车座椅坐盆骨架的成形需求为牵引，提出了通过预变形弱化镁合金板材基面织构同时改善基面织构分布沿ND的轴对称性的思路，进而改善镁合金板材的成形性。通过深入表征分析初始AZ31镁合金板材的力学特征，研究外加应力作用下板材基面取向偏转的宏观和微观演变机制及力学模型，研究基面取向分布的空间位置参数随应变量的变化规律，以及分布对称性的特征参数定量表达模型，从而建立外加应变量、微观力学、塑性变形机制和基面取向分布对称性之间的内在联系，获得具有合理的基面取向分布对称性的镁合金板材。通过成形基础研究，形成镁合金板材的成形力学本构模型和轻量化零部件成形技术原型，为轻量化零部件的装车验证奠定技术基础。

镁合金板材的基面织构很强，成形性差，现有织构调控可使镁合金基面c轴在一定程度上偏转或形成双峰织构，改善镁合金板材的单轴成形能力，但无法满足快速发展的汽车轻量化零部件的复杂成形要求。为此，本项目以汽车座椅坐盆骨架的成形需求为牵引，开展了镁合金板材的拉伸应力应变行为表征、预变形板材基面取向的调控、退火板材基面取向的微观结构与分布对称性分析、基面织构呈ND轴对称分布的镁合金板材的成形性能评价等研究工作。提出了通过预变形弱化镁合金板材基面织构同时改善基面织构分布沿ND的轴对称性的思路，进而改善镁合金板材的成形性。通过深入表征分析初始AZ31镁合金板材的力学特征弄清了外加应力作用下板材基面取向偏转的演变机制及微观力学模型，明确了基面取向分布对称性的几何参量和特征参数定量表达，建立了外加应变量、微观力学、塑性变形机制和基面取向分布对称性之间的内在联系，获得了具有合理的基面取向分布对称性的镁合金板材。通过成形基础研究，形成了镁合金板材的成形力学本构模型和轻量化零部件成形技术原型。在此基础上，以汽车镁合金座盆为典型零部件，开展镁合金板材零部件的服役评价与验证，系统测试镁合金板材的成形性能和成形后零部件的力学性能，为镁合金座盆的制备和成形工艺优化提供指导为轻量化零部件的装车验证奠定技术基础。