EBSD技术研究Ni-48Al金属间化合物超塑变形组织演变

EBSD Study on the Microstructural Evolution of Ni-48Al Alloy during Superplastic Deformation

摘要:

采用电子背散射衍射（EBSD）技术研究在1075 ℃、初始应变速率1.5×10-3 s-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。

Abstract:

The microstructural evolution of coarse-grained Ni-48Al alloy during superplastic deformation at 1075 oC with initial strain rate of 1.5×10-3 s-1 was studied using EBSD (electron back-scattered diffraction) technique. The results show that before deformation, high angle grain boundaries dominate in the coarse-grained Ni-48Al alloy with few low angle grain boundaries. During the superplastic deformation, low angle grain boundaries with misorientations less than 5° occur successively. With the increase of the deformation, the misorientations of the newly-formed low angle grain boundaries increase, low angle grain boundaries with misorientations between 6o-15° are formed, and finally high angle grain boundaries with misorientations larger than 15° are formed. There exists a sort of dynamic equilibrium between the formation rate of low-angle grain boundaries and the rate of changing into higher-angle grain boundaries. The transformation from low angle grain boundaries to high angle grain boundaries makes the number of high-angle grain boundaries increase continuously and finally the grains are refined markedly.