温度和应变幅对亚稳奥氏体不锈钢S321低周疲劳行为的影响

在室温和650 ℃的环境下对S321、S321H不锈钢进行了0.5%、0.7%、0.9%应变幅下的低周疲劳试验，并在室温下对S321和S321H开展了多个寿命点的疲劳加载历史试验，结合X射线衍射定量分析测算形变诱发马氏体的含量。结果表明： 形变诱发马氏体的生成会导致奥氏体钢持续循环硬化，室温下合金在初次硬化后继续二次硬化，而在650 ℃下没有形变诱发马氏体生成，合金在初次硬化后进入循环稳定阶段。循环过程中，碳含量越低，形变诱发马氏体含量越多，合金的循环硬化程度更高。两种温度下，两种材料的疲劳寿命在低应变幅下都相差不大，应变幅越大，两种材料的疲劳寿命相差越大，因此，可以考虑服役条件为低应变幅时使用S321不锈钢代替S321H不锈钢。

Effect of Temperature and Strain Amplitude on Low-cycle Fatigue Behavior of Sub-stable Austenitic Stainless Steel S321

Low-cycle fatigue tests were conducted on S321 and S321H stainless steels at 0.5%， 0.7%， and 0.9% strain amplitude at room temperature and 650 °C. Fatigue loading history tests were performed on S321 and S321H at room temperature for several life points， and the amount of deformation-induced martensite was measured by quantitative XRD analysis. The results show that deformation-induced martensite generation leads to continuous cyclic hardening in austenitic steels， and the alloys continue to secondary harden after the primary hardening at room temperature， whereas there is no deformation-induced martensite generation at 650 °C， and the alloys enter into cyclic stabilization phase after the primary hardening. The lower the carbon content during cycling， the more deformation-induced martensite there is， and the higher the degree of cyclic hardening of the alloy. At two temperatures， the fatigue life of the two materials in the low strain amplitude are not much different， the greater the strain amplitude， the greater the difference between the fatigue life of the two materials. Therefore， it can be considered to use S321 stainless steel instead of S321H stainless steel. Therefore， it can be considered to use S321 stainless steel instead of S321H stainless steel for service conditions of low strain amplitude.