Al-Cu合金中θ'相内位错运动导致的局部分解

Local decomposition induced by dislocations inside θ′ precipitates in Al-Cu alloy

利用透射电子显微镜(TEM)研究了等通道转角挤压变形(ECAP)后的Al-Cu合金的微观组织的演化。研究发现随着挤压道次的增加,基体晶粒细化,且析出相θ'逐渐发生局部分解。在1道次变形后,位错首先在θ'/Al基体的界面上产生并运动到相邻的θ'/Al基体界面上,基体中位错密度大大增加。在2道次变形后,基体中位错缠结形成沿剪切方向的亚晶界;同时塞积在θ'/Al基体界面上的位错导致θ'相内部产生很高的应力集中,从而使θ'相内部位错开动,θ'相弯曲,部分θ'相发生破碎现象。在3道次和4道次变形后,基体中的亚晶界逐渐转变为等轴晶;大量的θ'相无序排列,位错切割θ'相成小颗粒,且在位错滑移面周围θ'相发生局部分解。

The microstructural evolution of A1-Cu alloy after ECAP was investigated by transmission electron microscope, giving especial attention to the variation of θ＇ precipitates from the aspect of the morphology and chemical composition. With increasing passes of ECAP, grain refinement of A1 matrix and local decomposition of θ＇ precipitates occur. Dislocations nucleate at the interface between θ＇ precipitates and A1 matrix and move to neighboring the θ＇/A1 matrix interface after 1 pass of ECAP. Dislocation piling up at the θ＇/ A1 matrix interface induces high density of dislocation in A1 matrix. With increasing plastic strain after 2 pass of ECAP, heavily tangled dislocations are evolved into subgrain-boundary along the shear direction. High stress concentration is developed at the θ＇/A1 matrix interface and dislocation slip is activated inside θ＇ precipitates, inducing curving and fragmentation of plate-shape θ＇ precipitates. After 3 and 4 passes of ECAP, subgrain-boundaries are evolved into equiaxed grain boundaries. Plenty of θ＇ precipitates arrange in a disorder. Dislocations inside θ＇ precipitates shear θ＇ into fragmentations, with local decomposition occurring around slip plane inside θ＇ precipitates.