高塑性镁-铝-锡系镁合金塑性变形机制及形变亚结构演化行为

The Mg-Al-Sn system alloy is selected as the object originating from the decreased impact of Al and Sn dopings on the stacking fault energy of Mg. Concerning multi-element alloying based on this system, the key theoretical issues are to be investigated, including changing rules of plasticity microparameters with alloying elements doped, and functioning mechanism of doping elments on plasticity from atomic scale and electronic structure, which are both conducted by first principle calculations; also to be explored are the functioning impact of major alloying elements (Al, Sn) and microelements (Mn, Zn, Sb, RE etc.) on evolution behaviors of casting microstructure and recrystallization microstructure, plastic deformation behavior (yielding, hardening and softening), mechanisms of plastic deformation (slipping and twinning), together with evolution of deformation-induced submicrostructure. The present research is aimed i) to display precipitation sites and evolution mechanisms for precipitation phases (Mg2Sn etc.), as well as the interfaces between precipitation phases and matrix; to elucidate the slipping manner, twinning pattern and interaction between slip and twinning, together with formation and evolution mechanisms of subgrain boundry induced by slipping and twinning in the course of plastic deformation under room temperature; to reveal the influence of alloying elements, grain sizes and texture orientations on plastic deformation and evolution of deformation-induced submicrostructure; to achieve the estimation for mechanical properties and analysis of work harndeing ability, and actualize an optimization in composition design and preparation paramters (heat treatment, rolling etc.) for casting and roll-casting (rolling) magnesium alloys, thereby developing new Mg-Al-Sn alloys with independent intellectual property rights.

基于Al、Sn共掺降低Mg层错能，选取Mg-Al-Sn系合金为研究对象，从多元合金化出发，通过第一性原理计算研究合金元素掺杂下塑性微观参量变化规律，从电子结构角度揭示掺杂元素对塑性的作用机理，构建镁合金塑性预测微观物理模型；研究主合金元素（Al、Sn）和微量元素（Mn、Zn、Sb、RE等）与铸造组织和轧制后再结晶组织演变、塑性变形行为（屈服、硬化和软化）和机制（滑移和孪生）以及形变亚结构演化之间的作用关系。揭示沉淀相（Mg2Sn等）的析出位置及其与基体的界面关系和演变规律；揭示室温塑性变形过程中位错滑移方式和孪生模式及其交互作用以及位错和孪晶诱导亚晶界的形成和演化机制；揭示合金元素、晶粒尺寸和织构取向等对塑性变形行为及形变亚结构演变的影响规律；实施力学性能评价和硬化能力分析，优化铸造和轧制（铸轧）镁合金成分和制备参数（热处理、轧制等），发展自主知识产权新型高塑性Mg-Al-Sn系镁合金。

本项目基于Al、Sn共掺杂降低镁合金的层错能，选取Mg-Al-Sn系合金为研究对象，从多元合金化出发，通过第一性原理计算研究了合金元素掺杂下层错能等微观参量的变化规律，揭示出掺杂元素对塑性的作用机制，建立了镁合金塑性预测层错能模型；研究了主合金元素和微量元素与铸造组织和轧制后再结晶组织演变规律、塑性变形行为和变形机制（滑移和孪生）以及亚结构之间的关系。揭示了室温塑性变形过程中位错滑移方式和孪生模式及其形成和演化机制；给出了力学性能评价和加工硬化能力分析，优化了铸造和轧制镁合金成分和制备参数，提出了高变形能力细晶结构镁合金控制轧制技术，为发展自主知识产权的新型高性能镁-铝-锡系镁合金提供了借鉴。