中文摘要：

研究了相位角分别为30°，60°，90°以及等效应变幅分别为0．8％，0．6％，0．4％时双轴非比例加载下，冷变形去应力状态Zr-4合金的宏观响应和微观位错亚结构．结果表明：应力矢量和应变增量矢量之间的滞迟角θ在循环变形初期变化幅度较大；随着塑性变形的进行，变化幅度逐渐减小并趋于稳定．滞迟角的变化幅度与加载路径曲率的变化有关：90°相位角时变化幅度最小，30°相位角时变化幅度最大．在椭圆和圆形加载路径下，随着应变路径弧长△l的增大，等效应力的平均值升高，而变化幅度减小并渐趋稳定．随着相位角的提高，等效应力响应平均值升高．Zr—4合金在非比例加载过程中表现出初始硬化．随后持续软化的特征．随着相位角的提高，循环软化程度加剧．非比例循环过程中Zr-4合金的等效应力高于相同等效应变幅下的比例加载，表现出潜在强化特征．TEM观察表明：随着相位角的增加，Zr-4合金双轴疲劳位错亚结构由单个位错线向位错缠结及成熟的位错胞转化．材料内部各向同性强化机理加强是Zr-4合金非比例潜在强化的主要原因．

英文摘要：

Macroscopic response and microscopic substructure have been studied for the coldworked and stress-released Zr-4 alloy under biaxial out-of-phase loading with phase angles of 30°, 60°, 90° and equivalent strain amplitudes of 0.4%, 0.6%, 0.8%. The results show that the delay angle between stress deviation and strain increment vectors firstly exhibits a large variation range, and then drops to saturation as the plastic deformation processes. The variation range of delay angle depends on the curvature of loading path, and the variations have the minimum and maximum values at 90° and 30° phase angles, respectively. The average value of equivalent stress increases, however, its variation range decreases and reaches stability as the phase angle and equivalent strain amplitude increase. Zr-4 alloy displays an initial hardening followed by cyclic softening under out-of-phase loading. The Mises equivalent stress response curve of the alloy under out-of-phase loading lies above that under both uniaxial and in-phase loading. The alloy exhibits cyclic additional hardening under out-of-phase loading. TEM shows that the typical dislocation configuration changes from individual lines to tangles and embryonic cells as the phase angle and the equivalent strain amplitude increase. The isotropic hardening mechanism plays an important role in producing cyclic additional hardening.