连续流变挤压高Mg含量Al-Mg合金摩擦冷却下等轴晶与纳米相形成机理

高Mg含量Al-Mg合金在航空、汽车等领域具有重要应用前景，而常规方法制备的此类合金中含有粗大的枝晶与第二相，使其脆性大，深加工困难，制约了广泛应用。本项目有效利用连续流变挤压过程中摩擦剪切与冷却的耦合作用，改善熔体形核与长大的热力学与动力学条件，并使组织发生剪切破碎与再结晶细化，形成细小等轴晶和纳米第二相，比常规方法制备的合金力学性能大幅度提高，为解决上述瓶颈问题提供了有效解决方案。. 为揭示该过程中等轴晶与纳米相形成机理，拟研究连续流变挤压过程的摩擦剪切/冷却模型，摩擦剪切/冷却耦合下熔体传质机理、合金形核与长大机制、动态再结晶机制，以及影响摩擦剪切/冷却耦合作用的因素，优化工艺条件。以建立短流程调控高Mg含量Al-Mg合金组织的新方法及相关理论，制备高性能Al-Mg合金材料，为相关研究与技术开发提供依据。

Al-Mg alloys with high Mg content have important application prospects in many fields especially in aviation and automobile industries. However, the products of such alloys produced by conventional processing methods contain coarse dendrites and large second phases, which make the alloy brittle and difficult to carry out deep processing. Therefore, their applications are limited. The present project utilizes the coupling effect of frictional shear and cooling during continuous rheo-extrusion to improve the thermodynamic and kinetic conditions of nucleation and growth of the melt. At the same time, microstructure will be further refined by shear and recrystallization. Thus fine equiaxed grains and nanoscale phases could be obtained. Mechanical properties of the alloys are significantly improved by the present process as compared with conventional methods, and an effective solution to solve the above bottleneck problem is provided.. In order to reveal the formation mechanism of equiaxed grains and nanoscale phases during this process, we propose to study the shear and cooling models in continuous rheo-extrusion process, the mass transfer mechanism, the nucleation and growth mechanism, dynamic recrystallization mechanism under coupling effect of frictional shear and cooling, and optimize the process conditions. A new short processing method and the corresponding theory for microstructure controlling of Al-Mg alloys with high Mg content will be established. High performance Al-Mg alloys will be manufactured. The proposed project will provide the basis for the related research and technology development.