大晶粒Ni-42Al合金超塑变形中组织演变EBSD分析

A study of microstructural evolution of coarse-grained Ni-42Al alloy during superplastic deformation using EBSD analysis

采用电子背散射衍射（EBSD）技术,研究大晶粒Ni-42Al合金在1075℃、初始应变速率为1×10^-3s^-1条件下超塑变形中的组织演变。研究表明,变形前以大角度晶界为主,小角度晶界比例极低。在超塑变形中,持续有取向差5°以下的小角度晶界产生。随变形量的增大,新形成的小角度晶界取向差增加,转变为取向差较大的6°～15°小角度晶界,进而转变为15°以上的大角度晶界。小角度晶界的产生速率与小角度晶界转变为较大角度晶界的速率趋向一动态平衡。小角度晶界向较大角度晶界不断转变的结果使大角度晶界数量不断增加,最终导致晶粒显著细化。超塑变形使NiAl合金重合位置点阵（CSL）特征晶界发生改变,获得了有利于改善其室温塑性的CSL特征晶界结构。

The microstructural evolution of coarse-grained Ni-42Al alloy during superplastic deformation at 1075℃ with initial strain rate of 1 × 10^-3s^-1 was studied using EBSD technique. The results show that before deformation, the most grain boundaries are high angle boundaries, with several particular angles being predominant. During deformation, low angle grain boundaries with miserientation less than 5° occur successively. With increase of the deformation, of the newly-formed low angle grain boundaries increase, and grain boundaries with larger miserientation between 5 - 15° are formed, and finally high angle grain boundaries with miserientation larger than 15° are formed. There exists a sort of dynamic equilibrium between the formation of new low-angle grain boundaries and changing them into higher-angle grain boundaries. The forming of low-angle grain boundaries and turning them into higher-angle grain boundaries makes the number of high-angle grain boundaries increasing continuously. The results also show that super-plastic deformation results in the change of CSL characteristic grain boundaries of the coarse-grained Ni-42Al alloy, the CSL structure which is beneficial to improve plasticity of the alloy at room temperature was achieved.