Ag-Ni-Co(Fe)偏晶合金快速凝固过程研究

Ag-based Ag-Ni moneotectic alloys are excelent electric contactor materials. They are generally manufactured by using powder metallurgy technique due to their high binodal line temperature and high phase segregation tendency during solidification. The lack of the solidification theory of Ag-Ni system has limited the development of Ag-based contactor materials. Elements Fe, Co and Ni have similar properties. They do not dissolve in solid Ag at a temperature lower than 800℃ and they all form monotectic immiscible system with Ag and show a negligible solubility in solid Ag. It is possible to partly substitute Ni with Co/Fe and design Ag-Ni-Co/Fe alloys which remain the electric contacting properties of Ag-Ni, but show a lower binodal line temperature as well as a lower phase segregation tendency. This project will: 1) build up the thermodynamic data base and rapid solidification model of the Ag-Ni-Co alloys, probe into the microstructure formation mechanisms in the rapidly solidified Ag-Ni-Co alloys both experimentally and numerically, investigate the mechanical and electric properties of the rapidly solidified Ag-Ni-Co alloys, build up the principles for the design of the composition and solidification technologies of the Ag-Ni-Co alloys; 2) based on above research experience, study experimentally the rapid solidification behaviors of Ag-Ni-Co-Fe, investigate the mechanical and electric properties of the rapidly solidified Ag-Ni-Co-Fe alloys, build up the principles for the design of the composition and the solidification technologies of the Ag-Ni-Co-Fe alloys.

Ag基Ag-Ni电接触材料熔炼温度高、凝固时偏析倾向大，目前工业上用粉末冶金法制备。Ag-Ni系合金凝固理论的缺乏限制了该系合金的研发。元素Fe、Co、Ni性质相似，固态800℃以下均不溶于Ag，Ag-Ni-Co(Fe)具有与Ag-Ni相似的电接触性能。通过用Co、Fe部分代替Ni设计Ag-Ni-Co(Fe)合金，可在保证合金弥散相体积分数和合金性能条件下降低组元互溶温度和相偏析倾向，研发适于凝固制备的Ag基电接触合金。据此，本项目将：1)建立Ag-Ni-Co合金热力学数据库和快速凝固过程模型，实验与模拟相结合，揭示Ag基Ag-Ni-Co合金快速凝固机理，考察快凝合金的电学、力学性能，建立Ag-Ni-Co电接触合金成分及熔炼、凝固工艺设计原则；2)基于以上研究经验，实验研究Ag-Ni-Co-Fe合金凝固特性及电学、力学性能，建立Ag-Ni-Co-Fe电接触合金成分及熔炼、凝固工艺设计原则。

Ag基Ag-Ni电接触材料熔炼温度高、凝固时偏析倾向大，目前工业上用粉末冶金法制备。Ag-Ni系合金凝固理论的缺乏限制了该系合金的研发。本项目：1)开展了Ag-Ni-Co(Fe)合金热力学实验研究，并利用Calphad计算方法，拟合确定了Ag-Ni-Co(Fe)合金的组元混合自由能函数ΔGmix，建立了Ag-Ni-Co(Fe)合金相图；2)利用真空吸铸、喷铸、石墨模铸造等技术对Ag基Ag-Ni和Ag-Ni-Co合金开展了快速凝固实验，探索了合金成分与冷却速度等对合金组织及性能的影响；3)建立、完善了在弥散相液滴/粒子形核、扩散长大以及空间运动等因素共同作用下Ag-Ni和Ag-Ni-Co等偏晶合金快速/亚快速凝固模型；4)模拟与实验相结合，分析了合金成分和冷却速率等对合金凝固组织形成过程的影响，揭示了Ag-Ni-Co系合金快速/亚快速凝固组织形成机理，探索了合金凝固组织控制方法，发展了Ag-Ni-Co系合金快速凝固理论，为高性能Ag-Ni-Co系合金电接触材料的设计与凝固制备奠定了理论基础。