采用EBSD分析了1075℃和初始应变速率为8.75×10-4 s-1条件下大晶粒NiAl合金高温塑性变形过程中的组织演变 与重位点阵 (CSL) 特征晶界分布. 变形前大晶粒NiAl合金以大角度晶界为主, 小角度晶界比例极低. 在高温塑性变形过程中, 取向差5°以下的小角度晶界不断产生. 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转变为大角度晶界的速率趋向动态平衡. 小角度晶界向较大角度晶界不断转变导致晶粒显著细化. CSL特征晶界分析表明, 大晶粒NiAl合金高温塑性变形过程中, CSL晶界分布发生改变, 将对合金室温力学性能产生影响.
The microstructural evolution and the coincidence site lattice (CSL) characteristic grain boundary of coarse--grained NiAl alloy during plastic deformation at 1075℃ with the initial strain rate of 8.75×10-4 s-1 were studied using EBSD technique. Before deformation most grain boundaries are high angle boundaries, in which several particular angles are predominant, but low angle grain boundaries with misorientation less than 5° occurred successively during deformation. With the increase of the deformation, the misorientations of the newly--formed low angle grain boundaries increase, and grain boundaries with larger misorientation between 6°---15° are formed, and finally high angle grain boundaries with misorientation larger than 15° are formed. There exists a dynamic equilibrium between the formation rate of new low--angle grain boundaries and the rate of changing into higher--angle grain boundaries. Turning of low--angle into higher--angle grain boundaries results in the refinement of grains. The results also show that plastic deformation can change the CSL characteristic grain boundaries of the coarse--grained NiAl, which may improve mechanical properties of the alloy at room temperature.
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