新型双织构镁合金动静态力学特征演变及溯源机理研究

Compared with monolithic texture component, Mg alloys with multi-texture components have better plastic forming ability and lower anisotropy. Systematic research on dynamic/static mechanical behavior and deformation mechanism of Mg alloys containing a monolithic texture component are extensively studied, but studies on the alloy with bimodal texture have not been reported. In the present application, several important issues related to bimodal texture are systematically studied. Those issues include the effects of different texture component distribution on mechanical behavior and deformation mechanism, the rule and inner mechanism of dynamic/static strain rate influencing the competition of slip and twinning, stamping formability and deformation mechanism of bimodal textured Mg alloy. The aim of this projects involves quantifying the correlation between fraction of soft orientation and yield strength, further disclosing the influence of rate on such correlation, and developing a polycrystalline plastic model considering strain rate and texture factors. Meanwhile, the intrinsic mechanism of improving stamping performance by tailored bimodal texture is clarified. The results from this project can guides the plastic processing and deformation of magnesium alloys under complex service conditions.

与单织构组分相比，多织构组分具有更好的塑性成形能力及更弱的各向异性，目前对单织构镁合金的动、静态塑性变形行为及微观机制进行了大量系统研究，而双织构方面未有研究报道。本项目以新型双织构镁合金为研究对象，系统研究不同组分配比对双织构镁合金力学行为及变形机制的影响、动/静态应变速率影响孪生和滑移相互竞争的规律和机制、双织构镁合金冲压成形性能及其变形机制，揭示屈服强度随软取向比例变化的定量化关系，探寻应变速率对此量化关系的影响规律，发展融合应变速率因素和双织构因素的多晶塑性模拟模型，阐明双织构改善冲压成形性能的内在机理。本项目的研究成果可为镁合金塑性加工及其复杂环境下的服役提供重要的理论指导。

织构是影响镁合金力学性能的关键因素之一，研究织构调控与宏观力学性能的定量化关系具有重要意义。本项目针对单一强织构容易造成强烈的各向异性以及拉压屈服不一致性的问题，通过设计预压缩+热处理相结合的工艺参数成功在镁合金板材和棒材中制备了双织构组态镁合金，并以此双织构镁合金为研究对象重点开展了以下几个方面的研究：.（1）基于形变机制应变速率敏感性的双织构镁合金力学特征演变规律研究；.（2）应变速率对双织构镁合金微观变形机制及其组织演变的作用机理；.（3）双织构镁合金冲压成形性及其调控机制研究。.重要的研究发现包括：.（1）建立了双织构镁合金织构组分与变形参数的定量关系、双织构组分中软取向晶粒占比与屈服强度的定量化关系；.（2）揭示了双织构镁合金显著改善拉压屈服不一致性的机制，即诱导拉伸和压缩变形中启动相近比例的滑移和孪生机制；.（3）细致表征了双织构镁合金动、静态变形中的孪生行为，研究表明双织构组分可以激活更多的孪生变体，低施密特因子的孪晶会由于晶粒内部孪晶变体之间的应力协调作用而开启，而并非相邻晶粒之间的作用；.（4）发现双织构在450℃具有良好织构热稳定性，并且双织构可以在一定程度上提高镁合金耐腐蚀性。.（5）应变速率对镁合金力学性能有较大影响，超高速压缩变形屈服强度低于准静态压缩屈服，其主要原因是高应变速率更易于促进拉伸孪晶形核，低启动应力的{10-12}孪生的大量开启降低了屈服强度。.本项目发表SCI论文9篇，包括Acta Materialia 1篇、Journal of Magnesium and alloys 2篇。项目培养了硕士3名，在本领域重要学术会议做报告3次。