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.
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