Annealing softening is commonly observed in traditional coarse–grained materials. Herein, an annealing–induced hardening mechanism in selective laser melted 316L stainless steel (SLM–ed 316L SS) was investigated. The SLM–ed 316L SS, without prior cold–working history, displayed evident hardening behaviour as the annealing temperature increased from 400 °C to 500 °C. Several dedicated scanning transmission electron microscope and quasi–in–situ/electron backscatter diffraction techniques were employed to investigate the intrinsic characteristics evolution of the samples, including cellular/wall dislocation structure, nano–particles/segregation, dislocation density, crystallographic orientations, and low–angle grain boundaries (LAGBs).This phenomenon primarily arises from unique guardrail–like dislocation walls decorated with nano–particles (O, Cr, Mo, and Si) and a high proportion of LAGBs, hindering movement of dislocations and leading to their accumulation. Furthermore, this structure and the stable configuration of columnar crystals can synergistically affect the 500 °C annealed sample, resulting in a high yield stress of 628 MPa. On the other hand, complex deformation substructures, such as stacking faults, Lomer–Cottrell locks, and forest dislocations, also proliferated during deformation. These substructures enabled multiscale plastic strain partitioning, intensifying strain hardening and realizing a strength–ductility combination of a comparable yield/ultimate tensile strength of 628 MPa/789 MPa and tensile ductility of 32%. Dislocation motion was the dominant deformation mechanism based on the strengthening mechanism model in this study.

中文翻译：

---

对选择性激光熔化奥氏体不锈钢 316L 退火诱导硬化和变形机制的新见解


退火软化现象在传统的粗晶材料中很常见。在此，研究了选择性激光熔化 316L 不锈钢 (SLM–ed 316L SS) 的退火诱导硬化机制。 SLM-ed 316L SS 之前没有冷加工历史，当退火温度从 400 °C 升高到 500 °C 时，表现出明显的硬化行为。采用几种专用扫描透射电子显微镜和准原位/电子背散射衍射技术来研究样品的内在特征演化，包括细胞/壁位错结构、纳米粒子/偏析、位错密度、晶体取向和低位错密度。 – 角晶界（LAGB）。这种现象主要是由于独特的护栏状位错壁装饰有纳米颗粒（O、Cr、Mo和Si）和高比例的LAGB，阻碍了位错的运动并导致位错的积累。此外，这种结构和柱状晶体的稳定构型可以协同影响500℃退火的样品，产生628MPa的高屈服应力。另一方面，复杂的变形亚结构，如堆垛层错、洛默-科特雷尔锁和森林位错，也在变形过程中激增。这些子结构实现了多尺度塑性应变分配，强化了应变硬化，并实现了 628 MPa/789 MPa 的可比屈服/极限拉伸强度和 32% 的拉伸延展性的强度-延展性组合。在本研究中，基于强化机制模型，位错运动是主要的变形机制。