Cyclic deformation behavior of metastable austenitic stainless steel AISI 347 in the VHCF regime at ambient temperature and 300 °C
Cyclic deformation behavior of metastable austenitic stainless steel AISI 347 in the VHCF regime at ambient temperature and 300 °C
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DOI：
10.1016/j.ijfatigue.2021.106632
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发表时间：
2022-03-01
影响因子：
6
通讯作者：
Beck, Tilmann
中科院分区：
文献类型：
--
作者：
Daniel, Tobias;Smaga, Marek;Beck, Tilmann
由于瞬态材料行为和相关的明显自热效应，使用超声波疲劳测试 (USFT) 系统对亚稳态奥氏体不锈钢进行超高周疲劳 (VHCF) 测试具有挑战性。由于 USFT 中无法进行应力应变滞后的常规测量，因此无法以常规方式描述循环变形行为。因此，提出了一种基于能量的方法来表征奥氏体不锈钢在环境温度（AT）和高温下 VHCF 状态下的循环变形行为。因此，进行了原位耗散能量和温度测量。在 AT 下，两个值在循环加载过程中都会发生变化，而在 300°C 下，仅耗散能量发生变化。所研究的亚稳态奥氏体不锈钢 AISI 347 (X6CrNiNb1810, 1.4550) 在两个测试温度下均表现出高周疲劳 (HCF) 状态 (N-f < 10(7)) 的循环软化，从而导致样本失效。在 VHCF 状态下，观察到循环硬化，这导致达到负载循环的限制数量 N-1 = 2 x 10(9) 而没有样本失效。这种因应力幅值小幅减小而导致的循环变形行为的变化导致 VHCF 状态下的 Woehler 曲线出现水平方向，并导致所研究材料的真正耐久性极限。在 AT 中，使用磁性测量在所有疲劳样本中检测到铁磁 α'-马氏体。在 300 摄氏度时，只有达到极限循环次数而没有失效的样品才表现出少量的 α'-马氏体。
Very high cycle fatigue (VHCF) tests on metastable austenitic stainless steels using an ultrasonic fatigue testing (USFT) system are challenging due to the transient material behavior and associated pronounced self-heating effects. Because the conventional measurement of stress-strain hysteresis is not possible in USFT, the cyclic deformation behavior can't be described in a conventional manner. Hence, an energy-based approach is proposed for the characterization of cyclic deformation behavior of austenitic stainless steels in the VHCF regime at ambient temperature (AT) and elevated temperature. Therefore, in-situ dissipated energy and temperature measurements were performed. At AT both values underwent a change during cyclic loading, while at 300 degrees C only the dissipated energy changed. The investigated metastable austenitic stainless steel AISI 347 (X6CrNiNb1810, 1.4550) showed cyclic softening in the high cycle fatigue (HCF) regime (N-f < 10(7)) at both testing temperatures, which led to specimen failure. In the VHCF regime, cyclic hardening was observed, which resulted in reaching the limiting number of load cycles N-1 = 2 x 10(9) without specimen failure. This change in the cyclic deformation behavior by a small reduction of the stress amplitude led to a horizontal course of the Woehler curve in the VHCF regime and resulted in the true endurance limit for the investigated material. At AT, ferromagnetic alpha'-martensite was detected in all fatigued specimens using magnetic measurements. At 300 degrees C only specimens which reached the limiting number of cycles without failure exhibited a small amount of alpha'-martensite.