Abstract Macroscopic response and microscopic substructure have been studied for Zr-4 alloy in the cold-worked condition, which was subjected to biaxial out-of-phase loading with different phase angles of 30o 、60o 、90o and different equivalent strain amplitudes of 0.4%、0.6%、0.8%. The results show that the delay angle between stress deviation and strain increment tensor firstly exhibits a large variation range, and then drop to saturation as the plastic deformation processes. The variation range of delay angle depends on the curvature of loading path, it has the minimum value at 90o phase angle, and has the maximum one at 30o. The average value of equivalent stress increases, however, its variation range decreases to stable 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 stress response curve of Zr-4 alloy under out-of-phase loading lies above that under both unaxial and in-phase loading. It indicates that cyclic additional hardening is displayed in Zr-4 under out-of-phase loading. TEM examination shows that the typical dislocation configuration changes from individual dislocation lines to tangles and embryonic dislocation cells as the phase angle and the equivalent strain amplitude increase. The isotropic hardening mechanism plays an important role in inducing cycle additional hardening.
[1] Xiao L, Kuang Z B. Acta Mater, 1996; 44: 3059 [2] Doong S H, Socie D F, Robertson I M. ASME J Eng Mater Technol, 1990; 112: 456 [3] McDowell D L. J Mech Phys Solids, 1985; 33: 556 [4] Doong S H, Socie D F. ASME J Eng Mater Technol, 1991; 113: 23 [5] Nishino S, Naomi H, Masao S. Fatigue Fracture Eng Mater Struct, 1986; 9: 65 [6] McDowell D L, Stahl D R. Metall Trans, 1988 ; 19A: 1277 [7] Ilyushin A A, Stahl D R, Stock S R, Antolovich S D. Appl Math Mech, 1954; 18: 641 [8] Lamba H S, Sidebottom O M. ASME J Eng Mater Technol, 1978; 100: 96 [9] Shiratori E, Ikegami K, Kaneko K. J Mech Phys Solids, 1975; 23: 325 [10] Ohashi Y, Kurita T, Suzuki T. J Mech Phys Solids, 1981; 29: 51 [11] Zhao S X. PhD Dissertation, Xi'an Jiaotong University, 1996 (赵社戌．西安交通大学博士学位论文, 1996) [12] Xiao L, Umakoshi Y, Sun J. Metall Mater Trans, 2001; 32A: 2841 [13] Xiao L, Kuang Z B. Acta Metall Sin, 1998; 34: 242 (肖 林,匡震邦．金属学报,1998;34:242) [14] Xiao L. ASME J Eng Mater Technol, 2000; 122: 42 [15] Pochettino A A, Gannio N, Vial Edwards C, Penelle R. Scr Metall Mater, 1992; 27: 1859
