QP2相为主强化相的Al-Mg-Si-Cu合金析出演变原子尺度定量表征及强化机制

Al-Mg-Si-(Cu)铝合金是汽车轻量化的关键材料，提升现有合金性能和开发新合金对国产汽车轻量化意义重大。该类合金析出影响因素多、析出序列复杂，以β″为主强化相，存在成形性和烘烤硬化性难以兼顾的问题。前期工作证实QP2具有更好的强化能力及稳定性，但析出演变及强化机制尚不清楚。本项目设计以无序结构QP2相为主强化相的Al-Mg-Si-Cu合金，采用原子分辨率的HAADF-STEM、in-situ TEM、3DAP等和模拟计算方法开展以下研究：（1）合金成分对析出强化的影响规律，探明形成QP2相的最佳Mg/Si比和Cu含量；（2）时效过程中的原子团簇、各个析出相的形成和演变机制；（3）QP2相的形成机理和强化机制，建立QP2主强化相调控原则。获得以QP2相为主强化相的新型合金模型，提高合金的烘烤硬化性和热稳定性，为开发汽车用自主新型铝合金板材的设计提供新的思路和技术基础。

Al-Mg-Si-(Cu) aluminum alloy is the key material of lightweight car body. It has a significant meaning for improving the properties of existing Al-Mg-Si-(Cu) aluminum alloy and developing new alloys. The precipitation of this type of alloy with β″ as main strengthening phase is affected by many factors. Up to now, the alloy still exists the balance problem for obtaining good formability and bake hardening at the same time. Our recent work has proved that the QP2 phase has even better strengthening capability and thermal stability, but the precipitation and evolution and strengthening mechanism by QP2 is still unclear. In this proposal, we design the Al-Mg-Si-Cu alloy with a disordered QP2 phase as main strengthening phase, and by means of atomic resolution HAADF-STEM, in-situ TEM, 3DAP etc. and simulation method, carry out the following researches: (1) the effect of the alloy composition on the precipitation strengthening in order to find out the optimum Mg/Si ratio and Cu content for forming QP2 phase; (2) the formation and evolution mechanisms of the clusters, the precipitation in the alloy aging process; (3) the formation mechanism and strengthening mechanism of the disordered QP2 phase, establishing the control principle for QP2 phase as main strengthening phase. The research is expected to develop a new Al-Mg-Si-Cu model alloy mainly strengthened by QP2 phase, with improved bake hardenability and thermal stability, and also to provide new ideas and technical basis for development of the independent designed aluminum alloy sheet for car body application.