铝合金综合力学性能协同提高的微结构控制与模拟

A quantitative description of microstructural evolution and establishment of the semi-quantitative or quantitative relationship between microstructural evolution and mechanical properties for multi-component multi-phase alloys during processes is at the core of the materials science. So far, no systematic scientific methodology for simulating microstructural evolution of multi-component alloys quantitatively and controlling the complex microstructure feature with a desire to obtain optimal mechanical properties is available in the literature. . Using a wide array of simulation approaches (including phase field method and CALPHAD:CALculation of PHAse Diagrams) and state-of-the-art techniques (including transmission electron microscopy, three-dimensional atom probe, and mechanical property measurements), the major research tasks of the present proposal are: 1) to perform decisive experimental measurements of the multiscale structure and the corresponding mechanical properties (yield strength, elongation, fracture toughness) of Al-Mg-Si-Cu series Al alloys during the entire processing route from solidification to the age hardening, and to develop a scientific approach for obtaining thermophysical properties of metastable phases needed for the subsequent microstructural simulation; 2) to develop a novel phase-field crystal model for performing quantitative multi-scale simulation of microstructure evolution, and 3) to establish a scientific methodology for the semi-quantitative or quantitative description of the dynamic evolution of mechanical properties through the constitutive equations of mechanical properties in multi-component multi-phase alloys with the phase field-simulated microstructural parameters as major inputs. . It is highly expected that the completion of this project will solve crucial scientific issues associated with the quantitative description of microstructural evolution for multi-component multi-phase alloys, establish one novel strategy to control the complex mcirostructure feature for the sake of obtaining optimal mechanical properties of Al alloys, and provide important theoretic guidance on the development of new Al alloys.

多元多相材料的组织结构演变及其与力学性能的量化规律是材料学的核心。当前国际上缺乏定量描述多元多相材料结构演变及力学性能协同提高所需结构控制的系统科学方法。本项目拟通过相场、相图计算等模拟方法同透射电镜、三维原子探针及力学性能测定等实验相结合对Al-Mg-Si-Cu合金从凝固到时效强化全制备过程的结构演变及其与力学性能（屈服强度、延伸率和断裂韧性）的量化规律进行研究：1)铝合金制备过程中多尺度组织结构及力学性能随结构演变的测定，发展获得结构模拟所需亚稳相热物性的科学方法；2)建立多尺度特征的新晶体相场模型来定量描述各制备过程的结构演变；3)发展由结构参数为出发点，建立多元多相合金力学性能的本构方程来定量或半定量描述力学性能变化的科学方法。项目的完成可望为国际上提供一种描述多元多相材料结构演变的新方法，发展铝合金综合力学性能协同提高的微结构控制策略，并为开发新型铝合金奠定重要的理论基础。

铝合金由于其比强度高、成型性好、耐腐蚀等优异性能，因而是交通运算、航空航天等领域使用的重要结构材料。本项目全面地研究了Al-Mg-Si-Cu合金从凝固到时效全过程多尺度的组织结构演变及其与力学性能的量化规律。提出了定量描述多元多相材料结构演变及力学性能协同提高所需结构控制的系统科学方法。(1)首先从第一性原理计算出发对合金中团簇/GP区及亚稳相进行了预测，并结合低电压下的球差矫正透射电子显微观察首次确定了Bʹ相的结构模型。(2)其次，通过相场方法模拟了Al-Mg-Si-Cu合金凝固过程中枝晶的生长、第二相结构的演变以及析出相的形核生长。并从实验上测定了Al-Mg-Si-Cu合金关键第二相的力学性能。(3)研究了合金在轧制变形（热轧+冷轧）过程中晶粒度、再结晶行为、织构以及力学性能随轧制变形参数的演变规律；从原子尺度揭示了合金轧制后时效强化过程的析出行为，探究了析出相对合金力学性能和断裂行为的影响。(4)提出了一种快捷高效的纳米析出相的定量表征方法，然后耦合力学方程，实现了从多种析出相中分离单一析出相对合金强度的贡献。(5)最后基于上述研究结果，通过优化合金成分及处理工艺来调控Al-Mg-Si-Cu合金中的微结构，实现协同提高合金的强度和韧性，成功开发一种高强高韧的新型Al-Mg-Si-Cu合金。