摘要
在低温条件下，316L 奥氏体不锈钢 (ASS) 在保持高延展性的同时，还表现出卓越的强度，打破了传统的应力-应变权衡。尽管大量研究记录了奥氏体不锈钢的低温拉伸特性，但这一现象背后的基本机制在很大程度上仍未得到探索。本研究系统地重新审查了 316L 不锈钢在一系列低温（293 K、223 K、123 K 和 77 K）条件下的拉伸特性及其相关机制。利用电子反向散射衍射（EBSD）微观结构特征的结果，讨论了应力-应变平衡（GPa ∼ 80 %）优异的原因。结果毫无疑问地表明，转变机制，特别是从变形孪晶转变为马氏体转变（γ → ε → α′），在低温下增强伸长率方面起着至关重要的作用。在这些温度下，ε-马氏体和γ-奥氏体之间的吉布斯自由能差接近零，导致马氏体生长缓慢。低温下的应力-应变曲线符合康西德雷准则，表明在这些条件下出现了延迟缩颈现象。这种行为归因于各种分层微结构的存在，包括ε、α′、γ-孪晶、ε-孪晶及其交集，它们是加工硬化的来源。这项研究为了解 ASS 在低温条件下的变形行为提供了新的视角。At cryogenic temperatures, 316L austenitic stainless steel (ASS) exhibits remarkable strength while retaining high ductility, defying the conventional stress-strain trade-off. Despite extensive studies documenting the cryo-tensile properties of ASSs, the underlying mechanisms behind this phenomenon remain largely unexplored. This study systematically re-examines the tensile properties of 316L stainless steel and the associated mechanisms across a range of low temperatures (293 K, 223 K, 123 K, and 77 K). The reasons for the superior stress-strain balance (∼80 % GPa) are discussed using results from electron backscatter diffraction (EBSD) microstructure characteristics. The results undoubtedly suggest that the transformation mechanisms, specifically the shift from deformation twinning to martensitic transformation (γ → ε → α′), play a crucial role in enhancing elongation at cryogenic temperatures. At these temperatures, the Gibbs free energy difference between ε-martensite and γ-austenite approaches zero, resulting in slow martensite growth. The stress-strain curves at low temperatures satisfy the Considère criterion, indicating delayed necking under these conditions. This behavior is ascribed to the presence of various hierarchical microstructures, including ε, α′, γ-twins, ε-twins and their intersections, which act as sources of work hardening. This study provides new insights into deformation behavior of ASSs under cryogenic conditions.
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