Effect of Heat Treatment on Microstructures and Mechanical Behaviors of 316L Stainless Steels Synthesized by Selective L
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JMEPEG https://doi.org/10.1007/s11665-020-05330-7
Effect of Heat Treatment on Microstructures and Mechanical Behaviors of 316L Stainless Steels Synthesized by Selective Laser Melting Quanqing Zeng, Kefu Gan, and Yin Wang Submitted: 24 August 2020 / Revised: 13 October 2020 / Accepted: 31 October 2020 In this work, 316L austenite stainless steels were fabricated by the selective laser melting (SLM) technique, and the as-printed samples were then treated by using two various routines, namely the intercritical annealing (IA) and the deep cryogenic treatment (DCT), respectively. Microstructural characterization, nanoindentation creep tests as well as tensile experiments were also performed on the achieved specimens to evaluate the effect brought by the various heat treatment routines. It is found that DCT treatment produces a finer microstructure with higher quantity of homogenous tiny precipitates, compared with the as-printed SLM and single IA counterparts. Such microstructure of the DCT specimen leads to a desirable indentation creep resistance at room temperature as well as a good mechanical performance on tension. In addition, applying a prior deep cryogenic treatment before the intercritical annealing brings more positive effects on the mechanical properties than only using IA. The result indicates that the DCT routine is definitely considerably beneficial for fabricating reliable metallic products fabricated by selective laser melting, and it provides an efficient alternative in real manufactures as well. Keywords
deep cryogenic, fracture, intercritical annealing, microstructure, nanohardness, nanoindentation creep, selective laser melting, steel
1. Introduction Selective laser melting (SLM), as an additive manufacturing (AM) technique, has been widely used to produce structural components with intricate geometries and superior properties in real engineering (Ref 1-4). The fast heating/cooling cycle during SLM generates remarkably various microstructures from conventional manufacturing processes like casting, which significantly enhances the mechanical performance of materials (Ref 5-7). However, flaws like micro-cracks formed in the SLM-printed metals may induce a catastrophic failure on deformation, meanwhile microstructure coarsened by high heat input on printing would also deteriorate the mechanical properties of the SLM products (Ref 8, 9). Therefore, how to improve the quality of materials fabricated by SLM printing is a hotspot in the field of AM recently (Ref 10). A large number of optimizations on the printing parameters, including the laser power (Ref 11), the scanning speed (Ref 12), the spot size (Ref 13), the hatch spacing (Ref 14), the scanning strategy (Ref 6) Quanqing Zeng, Research Institute of Light Alloy, Central South University, Changsha 410083 Hunan, China; and Key Laboratory of the Ministry of Education of Nonferrous Metals, Central South University, Changsha 410083 Hunan, China; Kefu Gan, School of Materials Science and Engineering, Central South University, Changsha 410083 Hunan, China; and Y
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