Zr-4合金双轴疲劳行为及其微观变形机理 Ⅰ.双轴疲劳变形行为

BIAXIAL FATIGUE BEHMIOR AND MICROSCOPIC DEFORMATION MECHANISM OF ZIRCALOY-4 I. Biaxial Fatigue Deformation Behavior of Zircaloy-4

研究了不同主应变比比例加载和不同相位角非比例加载条件下 Ｚｒ－４合金双轴疲劳行为．结果表明：双轴比例和非比例循环变形过程中，在 Ｍｉｓｅｓ循环等效应力响应一循环周次曲线上，Ｚｒ－４均表现为循环初始硬化，随后逐渐软化特征． Ｍｉｓｅｓ循环等效应力－应变曲线均位于单调曲线的上方，表现为循环硬化特征．进一步研究表明：非比例加载过程中合金的循环强化程度高于相同等效应变下的比例加载，表现为非比例附加强化现象当主应变比为－０．６４，相位角为９０°时，非比例附加强化程度最高比例加载过程中，随着主应变比提高，疲劳寿命降低，非比例加载下合金的疲劳寿命低于相同等效应变幅下的比例加载．非比例附加强化程度越高，双轴疲劳寿命越低．

Biaxial fatigue behaviors of Zr-4 under in-phase (IP) with different principal strain ratio and out-of-phase (OP) loading with the phase angles of 30°, 60° and 90° were studied. The cyclic Mises stress response curves as a function of cyclic number consist of the cyclic first hardening and the following softening stages under IP and OP loading. The cyclic hardening is shown by the fact that the cyclic Mises stress versus strain curves lie above the monotonic one under IP and OP loading. The additional hardening is displayed under OP loading, since the hardening degree under OP loading is higher than that under IP loading at the same strain ranges. Zr-4 exhibits the highest degree of additional hardening, when the phase angle is equal to 90° and the principal strain ratio equal to-0.64. The biaxial fatigue life decreases as the principal strain ratio increases under IP loading. The fatigue life under OP loading is less than that under IP loading at the same equivalent strain ranges. The higher the additional hardening level, the lower the fatigue life under OP loading in comparison with that under IP loading.