Huang Ying-Ting, Yen Yu-Wei, Hung Fei-Yi
Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701401, Taiwan.
Materials (Basel). 2025 Jun 5;18(11):2654. doi: 10.3390/ma18112654.
This study investigates the microstructural evolution and mechanical degradation mechanisms of cold-drawn 310S stainless steel subjected to repeated thermal cycling between 900 °C and room temperature. The results reveal that thermal cycling induces significant lattice distortion, dislocation accumulation, and recrystallization, leading to grain refinement and increased tensile strength. However, these microstructural changes also initiate subsurface cracks and reduce ductility. TGA analysis confirms thermal weight loss from decarburization, especially under oxidative atmospheres. EPMA analysis and tensile tests after thermal cycling reveal that surface cracks formed during thermal cycling act as origins for transgranular crack propagation under tensile stress, significantly reducing fracture resistance. Bending fatigue tests further demonstrate that thermally fatigued specimens exhibit inferior fatigue life compared to raw material, confirming the deteriorating mechanical properties of 310S stainless steel after thermal cycling. Overall, the combined effects of thermal and mechanical fatigue degrade the structural integrity of 310S stainless steel, revealing that lattice distortion and subsurface cracking are the key factors in its embrittlement and reduced fatigue performance.
本研究调查了在900℃与室温之间反复热循环的冷拉310S不锈钢的微观结构演变和力学性能退化机制。结果表明，热循环会引起显著的晶格畸变、位错积累和再结晶，导致晶粒细化并提高抗拉强度。然而，这些微观结构变化也会引发亚表面裂纹并降低延展性。热重分析（TGA）证实了脱碳导致的热失重，尤其是在氧化气氛下。热循环后的电子探针微区分析（EPMA）和拉伸试验表明，热循环过程中形成的表面裂纹在拉伸应力下成为穿晶裂纹扩展的起点，显著降低了抗断裂性。弯曲疲劳试验进一步证明，与原材料相比，热疲劳试样的疲劳寿命较差，证实了热循环后310S不锈钢力学性能的恶化。总体而言，热疲劳和机械疲劳的综合作用降低了310S不锈钢的结构完整性，表明晶格畸变和亚表面裂纹是其脆化和疲劳性能降低的关键因素。
