To explore the effect of grain size on the tensile behaviour, symmetrical strain control fatigue behaviour and ratcheting fatigue behaviour of the new austenitic steel 316H, a series of tensile tests, symmetrical strain control fatigue tests and ratcheting fatigue tests were conducted at 25°C within an average grain size range from 14 to 122 μm. The average dislocation free path, forest dislocation density and mobile dislocation density of 316H steel with different grain sizes under tension were obtained. Moreover, the decrease of grain size led to saturation of mobile dislocations at lower strains. The decrease of grain size led to the increase of the cyclic stress and affected softening and secondary hardening process. In addition, under the same stress control conditions, the reduction in grain size caused a reduction in ratcheting strain under the same cycle. The grain refinement of 316H steel contributed to the improvement of ratcheting fatigue life.

中文翻译：

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316H奥氏体不锈钢的拉伸力学性能，变形机制，疲劳行为和疲劳寿命：晶粒尺寸的影响

为了探索晶粒尺寸对新型奥氏体316H钢的拉伸行为，对称应变控制疲劳行为和棘轮疲劳行为的影响，在25°C的温度范围内进行了一系列拉伸试验，对称应变控制疲劳试验和棘轮疲劳试验。平均晶粒尺寸为14至122μm。得到了不同拉应力下316H钢的平均位错自由程，森林位错密度和移动位错密度。此外，晶粒尺寸的减小导致在较低应变下移动位错的饱和。晶粒尺寸的减小导致循环应力的增加，并影响软化和二次硬化过程。此外，在相同的压力控制条件下，在同一循环中，晶粒尺寸的减小导致棘轮应变的减小。316H钢的晶粒细化有助于提高棘轮疲劳寿命。