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采用透射电镜观察了铁镍(Fe-32%Ni)合金在形变温度500℃(<0.5Tm)、形变速率10-2s-1的变形条件下多轴锻造变形过程中的微观结构演变。结果表明,低温多轴锻造强变形可明显细化晶粒,细化过程为:首先,位错墙、位错缠绕等结构通过大量位错滑移运动在原始晶粒内形成;其次,不同方向的变形导致不同方向的滑移系开动,从而致使不同方向的位错墙互相交叉,将原始粗晶粒细分成小尺寸的胞块结构,当变形量达到一定程度时,位错墙和位错缠绕结构内的位错开始重新排列,形成小角度晶界,导致亚晶粒形成;由于变形量不断增加强迫大量的位错在亚晶界处积聚、重排,同时不同方向的变形造成亚晶发生转动,位错重新规则排列及亚晶转动使小角度的亚晶界转变为大角度晶界,从而形成细小的新晶粒。
The microstructure evolution of the Fe-Ni-Ni (Fe-32% Ni) alloy during multi-axial forging deformation was investigated by transmission electron microscopy under deformation temperature of 500 ℃ (<0.5Tm) and deformation rate of 10-2s-1. The results show that the grain refinement can be obviously made by the strong deformation at low temperature and multi-axial forging. The refining process is as follows: Firstly, dislocation walls and dislocation winding are formed in the original grains through a large number of dislocation sliding motions. Secondly, Of the deformation leads to different directions of the slip system to start, resulting in different directions of the dislocation walls intersect each other, the original coarse grain subdivided into small size cell structure, when the deformation reaches a certain extent, the dislocation wall and bit The dislocations in the staggered structure begin to rearrange to form small-angle grain boundaries, resulting in the formation of subgrains. Due to the increasing deformation, a large number of dislocations are forced to accumulate and rearrange at the sub-grain boundaries, and the deformation in different directions causes sub-grains Crystal rotation occurs, dislocation reordered and sub-crystal sub-crystal rotation of the small-angle subgrain into large-angle grain boundaries, forming tiny new grains.