基于弥散相粒子组态调控的含镁高硅变形铝合金再结晶机制的研究

One of the problem in improvement the strength, plasticity and toughness of high silicon content wrought aluminum alloy is how to refine, equiaxed and uniform the grains of Al matrix, and properly control the configuration of second-phases particles in the alloy matrix. This proposal was based on the Mg contained high silicon wrought aluminum alloy, and the Mn(Ti) was selected as the alloying element to promote the in-situ precipitation of sub-micron dispersoid particles, on the basis of control the configuration of silicon, constituent and precipitate particles. The forming condition, evolution, and the control principle of the configuration of the dispersoid particles will be clarified. Furthermore, base on revealing the effect of the dispersoid particles on the flow behavior and the recrystallization of the alloy matrix, in association with the configuration of the silicon, constituent and precipitate particles, the mathematical physics model between the quantity, shape factor, dispersion, crystal structure of the dispersoid particles and the elastic modulus, flow stress, strain-hardening exponent, plasticity, fracture strength of the alloy will be preliminaril established. The studies might not only be helpful to establish the theory for reinforcing, plasticizing the high silicon content wrought aluminum alloy by dispersoid particles, but also to provide the scientific basis for optimizing the composition and the technology process of the high wrought Al-Si alloy as an high perfomance construction structural material. It is significant in enriching and developing the deformation and recrystallization mechanism of aluminum alloy.

如何使铝基体晶粒细小等轴均匀化，结合合理调控合金相粒子组态，是目前同时提高高硅变形铝合金强度、塑性及韧性亟待解决的关键问题之一。 本项目针对含镁高硅变形铝合金，在合理调控硅相、结晶相、析出相粒子组态基础上，通过Mn（Ti）合金化促进合金中原位生成亚微米级弥散相粒子，探明弥散相粒子的形成条件、演变规律及其组态调控原理，揭示在硅相、结晶相及析出相粒子协同作用条件下，弥散相粒子对合金基体塑性流变及再结晶行为的作用机理，演绎出弥散相粒子数量、形状因子、分布及晶体结构等与合金弹性模量、流变应力、加工硬化率、塑性及断裂强度间的数学物理模型。 研究结果不仅有助于构建利用弥散相粒子增强增塑高硅变形铝合金的理论体系，而且可为优化高性能结构材料型变形Al-Si铝合金成分及其相应的制备工艺参数提供科学依据，对丰富和发展铝合金形变及再结晶理论具有重要意义。

（1）揭示了DC铸造Al-12Si-0.7Mg合金铸锭中共晶Si相空间形貌为珊瑚状，在随后的485℃加热过程中共晶Si颗粒逐渐碎断并趋于球化，其直径d与485℃加热保温时间t满足t∝d2.29~2.67关系。.（2）揭示了Al-12Si-0.65Mg合金铸锭中存在α-Al、共晶Si、Mg2Si和π相(Al8Mg3FeSi6)，它们是分别在567℃通过L+Al5FeSi→α-Al+Si+Al8Mg3FeSi6、555℃通过L→α-Al+Si+Mg2Si及550-554℃通过L→α-Al+Si+Mg2Si+Al8Mg3FeSi6反应形成的；当合金中添加了Mn，α-Al枝晶明显细化，同时合金铸锭中出现α-Al(FeMn)Si相；当Mn的质量分数从0.10%增大至2.27%，α-Al枝晶形貌、尺寸及数量无明显变化，α-Al(FeMn)Si数量增多而尺寸不变；当Mn的质量分数达到1.07%，合金在647℃通过L+Al6Mn→α-Al+Al9Mn4Si3反应生成尺寸约80μm的Al9Mn4Si3，其中溶解了少量Fe形成为Al9(FeMn)4Si3，Mn含量增加其数量增多而尺寸不变；经550℃均匀化处理后，合金中的Mg2Si相溶入基体消失，共晶Si、π相和α-Al(FeMn)Si相球化成颗粒状，Al9(FeMn)4Si3相形貌、尺寸及数量几乎不变，Al-12Si-0.65Mg-(0.10~2.27)Mn合金基体中通过固态相变αˊ-Al→α-Al+Al9Mn2Si3析出尺寸约几百纳米的Al9(MnFe)2Si3弥散相粒子，其数量随Mn含量增加而增多。.（3）明确了Al-12.7Si-0.7Mg合金热轧板硅颗粒Ostwald粗化行为符合经典LSW理论：粗化早期，共晶硅颗粒半径的三次方与粗化时间r 3-t曲线呈抛物线关系；粗化时间延长，共晶硅颗粒的r 3与加热时间t近似呈线性关系。粗化温度升高，硅颗粒的粗化动力学常数增大。.（4）揭示了强化合金元素存在形式对Al-12.7Si-0.7Mg合金板材应变强化指数n值的影响规律：强化合金元素分别以固溶溶质原子、GP区、粗大平衡相和GP区+β＂相粒子存在于α-Al基体中时，板材的n值逐次减小。