Zr-4合金双轴疲劳行为及其微观变形机理 Ⅱ.双轴循环变形亚结构及其织构的发展

BIAXIAL FATIGUE BEHAVIOR AND MICROSCOPIC DE- FORMATION MECHANISM OF ZIRCALOY-4 Ⅱ. Cyclic Deformation Substructures and Texture Development

用透射电镜分别观察了Ｚｒ－４合金比例和非比例双轴疲劳变形亚结构结果表明：等效应变幅为０．８％；不同主应变比下，Ｚｒ－４合金比例双轴疲劳后典型的位错组态是｛１０１０｝柱面滑移产生的平行位错线随着等效应变幅提高，从平面状向波纹状滑移转化，有形成位错胞的趋势、非比例加载过程中，随着相位角从３０°增大到 ９０°，位错组态从平行位错墙变化成位错胞相位角为９０°时，随着等效应变幅提高，位错保持位错胞结构，但位错密度增高非比例变形前后织构分析表明：随着相位角提高，｛１０１０｝极点密度减弱，｛１０１１｝锥面极点密度增强，表明合金塑性变形从以 ｛１０Ｔ０｝柱面滑移为主向往面滑移加锥面滑移多系滑移转化．Ｚｒ－４合金非比例附加强化一方面是由于部分柱面滑移被锥面滑移取代后，滑移系本身临界分切应力提高；另一方面由于多滑移导致〈ａ／ａ〉和〈ｃ＋

Dislocation substructures of Zr-4 under in-phase and out-of-phase loading were observed by transmission electron microscope. The results reveal that the typical dislocation structure is parallel dislocation lines and dislocation bands produced by {1010} prismatic slip at the equivalent strain range of 0.8%, as the principal strain ratio increases. It changes from parallel dislocation lines to embryonic dislocation cells as the equivalent strain range increases. The typical dislocation configuration of Zr-4 under out-of-phase loading evolves from planar dislocation bands to cells when the phase angle changes from 30° to 90°. The dislocation substructure remains cells at the same phase angle of 90° and in different equivalent strain ranges. With increasing of phase angle the {1010} texture in the original specimens is weakened and {1011} texture is strengthened, indicating that the deformation mode of Zr-4 under out-of-phase loading changes from prism slip to prism slip together with pyramidal slippage. The mechanism of additional hardening can be attributed to the increase of critical resolved shear stress (CRSS) and the interaction between dislocations.