ABSTRACT

Selective laser melting (SLM), as a revolutionary technology for metal manufacturing, attracts tremendous attention because it can produce complex components to benefit the customised production. Here we report that additively manufactured 304L austenitic stainless steel (SS) with low stacking fault energy (SFE) show superior fatigue resistance than its conventional counterparts due to the unique heterogeneous microstructure despite containing relatively high porosity. A series of detailed microstructural characterisations were applied to systematically disclose the fatigue enhancement mechanism of additively manufactured parts. Direct evidence is offered to show the obvious progressive work hardening and strain rate hardening caused by the heterogeneous microstructure during cyclic deformation, thus enhancing the fatigue crack initiation resistance. The microstructural results reveal that the cellular substructure plays a decisive role in regulating the dislocation motion during cyclic deformation, resulting in the intergranular fatigue cracking along HAGBs rather than twin boundaries.

摘要

选择性激光熔化（SLM）作为一种用于金属制造的革命性技术，吸引了极大的关注，因为它可以生产复杂的组件，从而有利于定制生产。在这里，我们报告说，尽管具有相对较高的孔隙率，但由于具有独特的异质微观结构，因此具有低堆垛层错能（SFE）的增材制造的304L奥氏体不锈钢（SS）显示出比其常规同行更高的耐疲劳性。应用了一系列详细的微结构特征，以系统地揭示增材制造零件的疲劳增强机理。提供直接证据表明，由于周期性变形过程中异质的微观结构引起的明显的渐进加工硬化和应变速率硬化，因此，增强了抗疲劳裂纹萌生的能力。微观结构结果表明，在循环变形过程中，细胞亚结构在调节位错运动中起着决定性作用，导致沿HAGBs而不是孪晶边界的晶间疲劳裂纹。