铝合金及其复合材料在超塑变形过程中的正电子寿命谱

THE POSITRON LIFETIME SPECTRA OF AN AlALLOY AND A SiC_p-Al COMPOSITE

测量了２０２４Ａｌ及其复合材料超塑变形到不同应变量时的正电子寿命谱，讨论了缺陷数量随应变量的变化规律及缺陷类型的相互转化规律 同时也讨论了铝合金及其复合材料超塑变形过程中空洞形核机制、控制空洞长大的因素及微观缺陷对超塑性能的影响结果表明：２０２４Ａｌ合金中的缺陷数量先增加，当延伸率达到８０％后显著降低；变形过程中晶格缺陷从变形初期的空位（团）对或位错转变为变形后期的单空位或位错，并且空洞的尺寸也在随变形量在变化复合材料中的缺陷数量是先缓慢增加，延伸率超过８０％后急增，增到一定程度后缺陷数量基本不变；变形过程中晶格缺陷从变形初期的单空位或位错转变为变形后期的空位对（团）或位错，而空洞的尺寸变化不大２０２４Ａｌ合金的空洞形核主要通过空位集聚，空洞不断吸收沿晶界扩散来的空位而迅速长大，最终这些大空洞在垂直于拉伸方向连接导致材料的破坏；复合材料主要是通过位错在ＳｉＣ／Ａｌ界面塞积引起的高应力集中致使界面开裂，形成微空洞，空洞的长大受周围材料的塑变控制，随延伸率的增大。

The positron lifetime spectra of a 2024Al alloy and a SiCp-2024Al composite at differentsuperplastic elongations were measured. In the 2024Al alloy, the amount of defects increases at the initialstage of superplastic deformation (SD), then rapidly decreases after elongation reached 80%. At the sametime, the type of defects changes from double-vacancy (or vacancy-group) and dislocation to single-vacancy and dislocation. And the size of voids varies with the increase of the elongation. In the composite,the amount of defects slowly increases at first, then rapidly increases after elongation arrived at 80%,and basically remaines constant at later stage of SD. The type of defects varies from single-vacancy anddislocation to double-vacancy(or vacancy-group) and dislocation. And change of the void sizes is verysmall. At last, void nucleation mechanism, void growth control factor and the relationship between themicrostructural defects and superplasticity were discussed.