含金属间化合物相包晶合金的相选择及包晶反应机制研究

The present analyses on peritectic solidification are focused on phase selection and peritectic reaction mechanism. They are also mainly aiming at near/local equilibrium solidification of peritectic alloys containing solid solution phase at relatively lower cooling rates. However, for solidification of peritectic alloys containing intermetallic compound phase, the phase selection and peritectic reaction models which are based on near/local equilibrium solidification of peritectic alloys containing solid solution phase have many limitations. In previous study, the applicant has found that: the solidification characteristics of intermetallic compound phase influence the solidification behaviors of peritectic alloys containing intermetallic compound phase obviously; besides, temperature gradient can also influence the peritectic reaction as well as cooling rate. Therefore, the Sn-Ni/Sn-Mn peritectic alloys whose peritectic phase is intermetallic compound phase with certain/nil solubility are selected. First, the phase selection model for peritectic alloys containing intermetallic compound phase has been constructed by coupling with the solidification characteristics of intermetallic compound phase. Furthermore, the peritectic reaction model for peritectic alloys containing intermetallic compound phase has been constructed by coupling the factors such as temperature gradient, cooling rate, and solidification characteristics of intermetallic compound phase and so on. Thus, the solidification phenomena and mechanisms of peritectic alloys containing intermetallic compound phase can be more deeply understood. Theoretical basis can also be constructed to control the microstructure of peritectic alloys through these achievements of this project.

对包晶凝固的研究集中于相选择与包晶反应机制两方面，且主要针对低冷却速率时含固溶体相包晶合金的凝固，但对于含金属间化合物相包晶合金在较宽凝固速率范围内的凝固行为，以近/局域平衡和固溶体相为基础的包晶合金相选择模型及包晶反应机制存在局限。申请人在前期研究中发现：金属间化合物相的凝固特征显著影响含金属间化合物相包晶合金的凝固行为，同时，温度梯度与冷却速率等共同影响包晶反应过程。因此，本项目选择包晶相为有/无固溶度的金属间化合物相的Sn-Ni/Sn-Mn包晶合金作为研究对象，通过耦合金属间化合物相凝固特性，构建含金属间化合物相包晶合金的相选择模型；同时，耦合温度梯度、冷却速率与金属间化合物相凝固特性等因素，构建包晶反应动力学模型。项目成果为深入理解含金属间化合物相包晶合金的凝固现象与机制及其组织控制提供理论依据，具有重要理论和实际意义。

包晶凝固常见于各种重要的结构和功能材料，是一类重要的液固相变过程，其典型特征是：冷却时液相L与初生相α反应生成包晶相β。多数具有包晶反应的合金，其溶质组元在固相中扩散系数很小，所以，包晶反应往往不彻底，通常获得的包晶凝固组织中除包晶相外往往存在初生相等其他相。由于高温结构材料Ti-Al、Ni-Al，稀土永磁材料Nd-Fe-B及无铅焊料Sn-Ni等的研究和开发中均涉及到包晶反应，因此人们对于包晶合金的研究兴趣与日俱增。对包晶凝固的研究集中于相选择与包晶反应机制两方面，且主要针对低冷却速率时含固溶体相包晶合金的凝固，但对于含金属间化合物相包晶合金在较宽凝固速率范围内的凝固行为，以近/局域平衡和固溶体相为基础的包晶合金相选择模型及包晶反应机制存在局限。申请人在研究中发现：金属间化合物相的凝固特征显著影响含金属间化合物相包晶合金的凝固行为，同时，温度梯度与冷却速率等共同影响包晶反应过程。因此，本项目选择包晶相为有/无固溶度的金属间化合物相的Sn-Ni/Sn-Mn包晶合金作为研究对象，通过耦合金属间化合物相凝固特性，构建含金属间化合物相包晶合金的相选择模型；同时，耦合温度梯度、冷却速率与金属间化合物相凝固特性等因素，构建包晶反应动力学模型。项目成果为深入理解含金属间化合物相包晶合金的凝固现象与机制及其组织控制提供理论依据，具有重要理论和实际意义。