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采用电子背散射衍射(EBSD)技术研究在1075℃、初始应变速率1.5×10-3s-1条件下大晶粒Ni-48Al合金超塑变形过程中的组织演变。结果表明,变形前,大晶粒Ni-48Al合金以大角度晶界为主,小角度晶界比例极低。在超塑变形过程中,持续有取向差≤5°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6°~15°小角度晶界,进而转变为取向差>15°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。
Electron Backscattered Diffraction (EBSD) technique was used to study the microstructure evolution during the superplastic deformation of large grain Ni-48Al alloy under the initial strain rate of 1.5 × 10-3s-1 at 1075 ℃. The results show that the large grain Ni-48Al alloy is dominated by large-angle grain boundaries and the angle of the small-angle grain boundaries is very low before deformation. In the process of superplastic deformation, there are continuous small angle grain boundaries with orientation difference ≤5 °. With the increase of the deformation, the newly formed small-angle grain boundary orientation difference increases and transforms into a small angle grain boundary with a difference of orientation of 6-15 °, and further transforms into a large-angle grain boundary with a difference of orientation> 15 °. 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.