基于晶粒细化的Al-Si基铸造合金的组织与铸造缺陷调控机理

Al-Si基铸造合金是航空、航天、交通运输等轻质结构件制造领域应用最广泛的一类铸造铝合金。晶粒细化是综合调控铸件微观组织及铸造缺陷的关键手段。然而，此类铸造合金尚缺少有效的基于晶粒细化的微观组织及铸造缺陷综合调控手段，导致其铸件质量及性能大幅提升面临巨大瓶颈。本项目拟通过新一代抗Si毒化Al-Nb-B细化剂在Al-Si基铸造合金中的应用，探索此类合金基于晶粒细化的微观组织及铸造缺陷调控机理。项目拟采用实验、理论建模及计算机模拟相结合的方法，揭示细化剂细化效果随时间衰减的机理及控制要素，阐明晶粒细化对合金微观组织及铸造缺陷形成及演化的影响机理及调控机制，在此基础上，针对典型铸件，开展耦合细化剂添加及铸造成形工艺的微观组织和铸造缺陷综合调控，形成具有普适性的调控原理和方法。该研究不仅对铸造合金微观组织及铸造缺陷控制理论发展有重要意义，还有望突破制约此类合金铸件质量及性能大幅提升的瓶颈。

Al-Si foundry alloys are widely used to manufacture high performance and light castings in the fields of aircrafts, spacecrafts, and vehicles, etc. Grain refinement has been well known as an effective approach in modulation of microstructures and casting defects of casting alloys. However, since there is lack of efficient way in modulating microstructures and casting defects of the Al-Si foundry alloys via grain refinement, an effective improvement of quality and performance of the Al-Si based castings has become a bottleneck in the relevant fields. Aiming to solve this problem, this project focuses on proposing an effective approach for modulating microstructures and casting defects of the Al-Si foundry alloys by applying a novel anti Si poison Al-Nb-B grain refiner. The investigation will be conducted by a combination of experimental investigations, theoretical modelling and computer simulations. First, the mechanism and the dominant factors of the fading of the Al-Nb-B grain refiner with time in the Al-Si foundry alloys will be illuminated. Second, the influence of grain refinement on the formation and evolution of the microstructures and casting defects will be elucidated. Accordingly, the strategies of the modulation of microstructures and casting defects based on the combination of grain refiner addition and casting processing parameters will be proposed. On this basis, the modulation of microstructures and casting defects of typical Al-Si castings will be carried out under actual processing conditions. The produced castings will be examined and the applicability of the proposed strategies will be evaluated. This study will not only be highly scientific meaningful for the theory of microstructure and casting defect control of the Al-Si based casting alloys but also be helpful in breaking through the bottleneck that restrict the significant improvement of quality and performance of the Al-Si based castings.