双峰分离非基面织构AZ31镁合金板材的室温轧制变形机理多尺度研究

As to AZ31 magnesium alloy sheet fabricated by the conventional plastic processing technology, the poor deformability at room temperature results from its forming stable basal texture, and therefore its maximum deformation degree per pass in the process of rolling at room temperature has never exceeded 22%. However, in the present study, based on the technique of equal channel angular rolling-continuous bending (ECAR-CB), AZ31 magnesium alloy sheet with the bimodal non-basal texture is fabricated, in which the basal poles are completely separated. As a result, its maximum deformation degree per pass in the process of rolling at room temperature has reached 32%, which illustrates that the unfavorable effect of basal texture on the deformability in the process of rolling at room temperature can be basically eliminated, and moreover the breakthrough with regard to bottleneck in the application of traditional wrought magnesium alloy is overwhelmed with expectation. However, deformation mechanisms of AZ31 magnesium alloy sheet with this kind of special non-basal texture are still not clear. Therefore, from the macroscale, mesoscale, microscale and nanoscale perspective, by combining microstructure characterization experiment of materials and crystal plasticity finite element simulation, it shall be able to lay the theoretical and technical foundations for the industrial production of magnesium alloy sheet with perfect properties by means of exploring the basic laws of microstructure evolution of sheet in the case of rolling at room temperature, analyzing the interaction mechanisms between dislocation and dislocation, between dislocation and twin, between twin and twin, between dislocation and grain boundary during rolling process of sheet at room temperature, establishing the crystal plasticity constitutive model in consideration of the synergetic interaction between dislocation and twin, revealing the deformation mechanisms of AZ31 magnesium alloy sheet with the bimodal non-basal texture in the process of rolling at room temperature.

传统塑性加工工艺制备的AZ31镁合金板材具有较强的基面织构，导致室温变形能力较差，表现为室温单道次轧制最大变形量不超过22%。而本项目通过等径角轧制-连续弯曲（ECAR-CB）工艺制备的板材具有双峰完全分离的非基面织构，其室温单道次轧制变形量高达32%，基本消除了基面织构对室温轧制变形能力的不利影响，有望突破传统变形镁合金板材应用的瓶颈。然而，这种特殊非基面织构板材室温轧制变形机理尚不清楚。因此，本项目拟从宏观、介观、微观和纳观等多尺度出发，将材料微观表征实验和晶体塑性有限元模拟相结合，研究板材室温轧制变形微观结构演化规律，分析板材室温轧制过程中位错与位错、位错与孪晶、孪晶与孪晶、位错与晶界的交互作用机制，建立基于位错滑移和孪生协同作用的晶体塑性本构模型，揭示双峰分离非基面织构AZ31镁合金板材的室温轧制变形机理，为高性能镁合金板材的工业化生产奠定理论与技术基础。

AZ31镁合金板材由于其密排六方的晶体结构导致在室温条件下的独立滑移系有限，且在传统塑性加工制备过程中容易形成较强的基面织构，使得板材后续室温塑性变形能力较差，具体表现为室温单道次轧制最大变形量不超过22%。而本研究项目中通过等径角轧制-连续弯曲-退火（ECAR-CB-A）工艺制备的AZ31镁合金板材，具有由ND向RD偏转45°左右非常罕见的双峰分离非基面织构。该特殊非基面织构的存在，将AZ31镁合金板材的室温单道次轧制变形量显著提高到高达32%，基本消除了基面织构对室温轧制变形能力的不利影响，有望突破传统变形镁合金板材应用的瓶颈。为深入揭示这种特殊非基面织构板材室温轧制变形机理，本项目以ECAR-CB-A工艺制备的双峰分离非基面织构AZ31镁合金板材为研究对象，采用单道次室温轧制工艺，从宏观、介观、微观和纳观等多尺度出发，研究了板材室温轧制变形微观结构演化规律，分析了板材室温轧制过程中位错与位错、位错与孪晶、孪晶与孪晶、位错与晶界的交互作用机制，建立了基于位错滑移和孪生机制协同作用的晶体塑性本构模型，最终阐明了双峰分离非基面织构AZ31镁合金板材的室温轧制变形机理，为高性能变形镁合金板材的工业化生产奠定理论与技术基础。