基于累积叠轧技术的alfa/beta交替镁锂合金板材组织与性能调控研究

In this project, it is proposed to roll the α(Mg) single phase Mg-Li plate and β(Li) single phase Mg-Li plate with the method of accumulative roll bonding(ARB). Besides the normal advantage of microstructure refining, two other advantages will be realized. Firstly, because of the different plasticity between α(Mg) and β(Li), the twist rolling zone will be formed even under the synchronous rolling. The other advantage is that, during the process of ARB, at the boundary between the α(Mg) single phase Mg-Li plate and β(Li) single phase Mg-Li plate, Mg atoms and Li atoms will spread mutually, and the phases of α(Mg) and β(Li) will transfer to each other. Accordingly, the dual phase zone with good comprehensive mechanical properties will be formed at the boundary. Therefore, the high property superlight Mg-Li alloy will be obtained with ultra-fine grains and good bondings between plates. What's more, the microstructure evolution and texture evolution of α(Mg) and β(Li) during the process of ARB, the characters and formation mechanisms of twist rolling zone, and the formation mechanisms of the dual phase zone boundary will also be revealed.

本项目提出对具有α(Mg)单相和β(Li)单相的两种镁锂合金板进行复合累积叠轧(ARB), 在实现常规ARB的技术优势（晶粒细化）基础上,在普通同步轧机条件下利用α(Mg)相和β(Li)相之间的塑性变形能力差异实现“搓轧区”的形成;利用α(Mg)单相合金板与β(Li)单相合金板之间的界面在热变形过程中镁和锂之间的相互扩散以及α(Mg)和β(Li)之间的相互转化,在界面处形成强韧性优良的“双相区”。以期获得具有超细晶组织、叠层之间界面结合良好的高性能超轻镁锂合金。揭示ARB过程中,α(Mg)相和β(Li)相的组织演变和织构演变规律、“ 搓轧区”的组织特征及其形成机理、“双相区”界面的形成机理等科学问题。

Mg-Li合金作为超轻金属结构材料，由于Li含量不同，Mg-Li合金形成了不同塑性变形能力的a-Mg相和β-Li相。通过优化累积叠轧（ARB）工艺，制备了超细晶的a-Mg/β-Li交替复合镁锂合金，然后进一步研究了ARB及其退火过程中Mg-Li复合板材的微观组织、织构和力学性能的演变，并通过分析得出a-Mg相和β-Li相的再结晶机制和“ 搓轧区”、界面“双相区”的形成机理。结果表明，在ARB过程中，a-Mg相和β-Li相的晶粒具有“双晶”特征，可促进两相协调变形，而且由于“搓轧区”的形成及退火过程中Mg原子和Li原子的扩散，复合板材界面结合效果良好。Mg-5Li-1Al合金的织构类型为典型的镁合金轧制织构，织构强度随着轧制道次的增加先升高后降低， Mg-12Li-1Al合金的变形主要表现为（110）中温滑移面的滑移，（321）高温滑移面随着轧制累积应变量的增加也有所激活。ARB6复合板材经过400℃30min退火处理后具有最佳综合力学性能，且界面处形成两层扩散区域，其组成为Li3Mg7 和Li0.92Mg4.08相，因此复合板材组织呈Li3Mg7 相、Li0.92Mg4.08相和Li3Mg17相交替分布。