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采用EBSD分析技术研究1075℃、初始应变速率为1×10-3s-1试验条件下大晶粒Ni-42Al合金超塑变形过程中的组织演变。研究发现,变形前大晶粒Ni-42Al合金中小角度晶界比例极低,均以大角度晶界为主,且某几个特定角度的大角度晶界占有明显优势。在超塑变形过程中,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5~15°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。
The EBSD analysis was used to study the microstructure evolution of the large grain Ni-42Al alloy during the superplastic deformation at 1075 ℃ and the initial strain rate of 1 × 10-3s-1. The results show that the proportion of small-angle grain boundaries in the large grain Ni-42Al alloy before deformation is extremely low, both of which are dominated by large-angle grain boundaries, and the large-angle grain boundaries at certain specific angles occupy obvious advantages. During the process of superplastic deformation, there are continuous small-angle grain boundaries with orientation difference below 5 °. With the increase of the deformation, the newly formed small-angle grain boundaries increase the orientation difference, and transform into small angle grain boundaries of 5-15 ° with larger difference of orientation, and then turn into large-angle grain boundaries of 15 ° or more. The rate of formation of small-angle grain boundaries and the rate of transition from small-angle grain boundaries to larger-angle grain boundaries tend to be a dynamic equilibrium. As a result of the continuous transformation of the small-angle grain boundaries to the larger-angle grain boundaries, the number of large-angle grain boundaries is continuously increased, leading to a significant grain refinement.