镁合金电致塑性轧制织构优化的合金化效应研究

The ductility of magnesium (Mg) alloys at room temperature largely depends on crystallographic texture, making texture modification a key to formability improvement. The present author found in the previous research that modified texture can be obtained in Mg-3Al-1Zn alloy via electroplastic rolling. However, the responsible mechanisms are still far from clear. In this work, Mg-3Al-1Zn alloy and pure Mg will be rolled both with/without the assistance of pulsed electric current. The microstructure and texture evolution of the two materials under the two different processes will be studied. Three dimensional atom probe (3DAP), mechanical testing at micro/nano scale and first principle calculations will be employed to reveal the effect of pulsed electric current on the distribution of solute atoms (Al and Zn) and how the distribution would influence the slip/twinning behavior. Through crystal plasticity modeling, connections between slip/twinning behavior and the texture formation will be established. The deformation mechanisms of Mg-3Al-1Zn alloy under pulsed electric current will be elucidated based on the experimental and modeling results, from which the principles to control the texture of Mg alloys during electroplastic rolling will also be proposed.

镁合金的室温塑性受织构影响显著，因此织构优化是提高其室温成形性能的关键所在。前期研究表明，与传统轧制相比，在轧制的同时施加脉冲电流能够在Mg-3Al-1Zn合金中获得更加有利于后续成形的织构，然而其内在机制尚不清楚。本课题将针对Mg-3Al-1Zn合金和纯镁，通过开展电致塑性轧制和普通加热轧制对比实验，研究两种材料在有/无脉冲电流辅助的轧制过程中的微观组织演变差异及其与最终织构之间的关联。尝试采用三维原子探针表征、微纳米尺度力学测试并结合第一性原理计算，从原子尺度揭示脉冲电流对Mg-3Al-1Zn合金中溶质原子Al和Zn的空间分布的影响以及该分布对材料滑移/孪生行为的影响；基于晶体塑性模拟，建立起滑移/孪生行为与织构演变之间的对应关系，从而阐明脉冲电流影响镁合金塑性变形的内在机理，并提出基于电致塑性轧制的镁合金织构调控原则。本项目的研究结果能够丰富外场作用下镁合金的塑性变形和织构形成理论。

镁合金的室温塑性受织构影响显著，因此织构优化是提高其室温成形性能的关键所在。本项目提出采用高能脉冲电流辅助加工的手段来优化镁合金板材的织构。本项目不需要昂贵的稀土或其它合金化元素，也不要增加额外的加工工序即可有效的实现织构优化效果。同时，本项目重点研究了脉冲电流对镁合金当中孪生、滑移以及再结晶等行为的影响机制。取得的主要研究成果有: 1) 揭示了脉冲电流对镁合金{10-12}和{10-11}孪生行为的影响规律，及{10-12}孪晶界对镁合金室温塑性变形的影响规律; 2) 阐明了脉冲电流对镁合金当中几种不同滑移模式的影响规律; 3) 探索了镁合金在电致塑性轧制及脉冲电流退火过程中的织构演化规律及调控策略。本项目的研究成果丰富和发展了镁合金在外场辅助下的塑性变形与再结晶的理论，可以为高塑性镁合金的低成本、高效率制备提供新思路和理论指导。