Dependence of dynamic strain ageing on strain amplitudes during the low-cycle fatigue of TP347H austenitic stainless steel at 550 degrees C

作者：Zhou HongWei^*; He YiZhu; Cui Mian; Cen YuWan; Jiang JianQing

来源：International Journal of Fatigue, 2013, 56: 1-7.

DOI：10.1016/j.ijfatigue.2013.07.010

• TP347H austenitic stainless steel
• Dynamic strain ageing
• Low-cycle fatigue
• Cyclic stress response
• Dislocation structure

Low-cycle fatigue (LCF) tests are carried out on TP347H stainless steel at a strain rate of 8 x 10(-3) s(-1) with total strain amplitudes (Delta epsilon(t)/2) of +/- 0.4% and +/- 1.0%, at room temperature (RT) and 550 degrees C. It is found that the stress responses and dislocation structures under cyclic loading strongly depend on the value of strain amplitude at 550 degrees C. Compared with those at the same strain amplitude at RT, the material shows a rapid strain softening, and finally attains a stabilized state at Delta epsilon(t)/2 = 0.4% and 550 degrees C, but the one presents an anomalous behavior, i.e., first a rapid hardening to the maximum stress, followed by a reducing softening at Delta epsilon(t)/2 = 1.0% and 550 degrees C. More cells resulting from dislocation cross-slip and planar structures due to dynamic strain ageing (DSA) restricting cross-slip develop at low strain amplitude of 0.4% at the first cycle. However, there are more complicated dislocation structures, such as cells, elongated cells, walls/ channels and planar structures at Delta epsilon(t)/2 = 1.0%. The observations of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) exclude the effects of martensitic transformation, creep, oxidation, and precipitations on these stress responses and microstructure evolutions, which result from DSA appearing at 550 degrees C.

• 出版日期2013-11
• 单位东南大学; 安徽工业大学