High temperature stress relaxation behavior of high Si, Mo-doped austenitic stainless steels

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 916; p. 147330
• Main Authors: Zhang, Shuzhan, Zhu, Heyu, Su, Yuanfei, Shi, Xianbo, Liu, Peitao, Yan, Wei, Rong, Lijian, Yang, Ke
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2024
• Subjects: Ferrite; G phase; High Si austenitic stainless steel; Stacking faults; Stress relaxation; Twins; High Si austenitic stainless steel; Mo; Stress relaxation; G phase; Ferrite; Stacking faults; Twins
• ISSN: 0921-5093
• DOI: 10.1016/j.msea.2024.147330

The resistance to stress relaxation at high temperatures is of importance to fasteners. In this study, the stress relaxation behavior of high Si, Mo-doped austenitic stainless steels at 450, 510, 550, 600 and 650 °C were investigated, taking the microstructure evolution at high-temperature long-term condition into account. It is found that Mo can effectively mitigate the plastic strain rate at high temperatures by impeding the extension of partial dislocations, thus leading to a noteworthy enhancement in the stress relaxation resistance. The first-principles calculations indicated that the addition of Mo can suppress the formation of a multi-phase composed of G phase and ferrite at high temperatures, by increasing the segregation energy of Si, Cr, and Ni at grain boundaries. This multi-phase induces the formation of stacking faults and twins, and therefore is responsible for an abnormal reduction in the residual stress.