等径角轧制-连续弯曲变形镁合金板材退火再结晶行为及特殊非基面织构形成机理

For conventional rolled magnesium alloy sheets, the low formability at room temperature due to the forming stable basal texture limits their widespread application. After annealing for Equal Channel Angular Rolling-Continuous Bending (ECAR-CB) wrought AZ31 magnesium alloy sheets, a special non-basal texture, in which the two basal poles are completely split, might form. As a result, the adverse effect of basal texture on the formability can be basically removed and it is expected to break through the application bottleneck of wrought magnesium alloy sheets. However, the key science problems, including the mechanisms, key influence factors and their action mechanisms of this special non-basal texture formation, are still not clear. Accordingly, the project intends to select AZ31 magnesium alloy sheets as the study object, use quasi in-situ EBSD and other means, emphatically carry out the studies, including the influence rules and mechanisms of deformation microstructures and textures and annealing process factors on the annealing recrystallization microstructures and textures, evolution microscopic processes and mechanisms of annealing recrystallization microstructures and textures, internal relations between annealing recrystallization microstructures, textures and cold formability. Precise control of microstructures, textures and properties of ECAR-CB magnesium alloy after annealing would be achieved. Results can lay the theory and technical foundations for the industrial production of high formability magnesium alloy sheets.

变形镁合金板材在常规轧制过程中容易形成较强的基面织构，导致其室温成形性能较差，从而限制了其大规模应用。采用等径角轧制-连续弯曲变形（ECAR-CB）及再结晶退火工艺，在退火AZ31镁合金板材中能够获得一种双峰完全分离的特殊非基面织构，基本消除了基面织构对成形性能的不利影响，有望突破变形镁合金板材应用的瓶颈。然而，这种退火再结晶特殊非基面织构形成的机理、关键影响因素及作用机制等关键科学问题尚不清楚。有鉴于此，本项目拟以AZ31镁合金板材为研究对象，采用准原位电子背散射衍射等多种手段，深入开展ECAR-CB板材形变组织与织构以及退火条件等因素对退火再结晶组织与织构的影响规律及机制、退火再结晶组织与织构演变的微观过程及机制、退火再结晶组织及织构与室温成形性能之间的内在关联等研究，实现退火ECAR-CB镁合金板材组织、织构及性能的有效调控，为高成形性能镁合金板材的工业化生产奠定理论与技术基础。

轧制是变形镁合金板材一种常用的制备加工方法。然而，轧制变形AZ31镁合金板材容易形成强基面织构，严重恶化其室温成形性能，很大程度上限制了其应用。采用等径角轧制-连续弯曲（ECAR-CB）变形及再结晶退火工艺，可以消除AZ31镁合金板材中的基面织构，能够获得一种双峰分离的非基面织构特征，从而提升了板材室温成形性能。本项目为了搞清ECAR-CB AZ31镁合金板材中双峰分离非基面织构的形成机理，采用了准原位电子背散射衍射（quasi-in-situ EBSD）等多种手段，研究了ECAR-CB板材变形组织与织构等因素对退火再结晶组织与织构的影响及规律，建立了退火再结晶组织织构与室温成形性能之间的关系，研究了双峰分离非基面织构板材室温成形过程中组织与织构的演变规律，探讨了双峰分离非基面织构提升镁合金板材室温成形性能的内在机制，分析了退火再结晶组织与织构演变的微观过程，揭示了双峰分离非基面织构的形成机理，实现了ECAR-CB变形及退火镁合金板材组织、织构及成形性能的有效调控。项目研究成果不仅进一步丰富了变形镁合金板材织构设计与优化理论，而且有助于变形镁合金板材的推广应用。