Grain boundary character distribution in the CoCrMo alloy processed by selective laser melting and post-heat treatment
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Grain boundary character distribution in the CoCrMo alloy processed by selective laser melting and postheat treatment Haoqing Li1,2, Shuai Shao1,2, Xuepeng Ren1,2, Hong Guo3, Dianjun Lou4, Weilong Xia4, and Xiaoying Fang1,2,* 1
School of Mechanical Engineering, Shandong University of Technology, Zibo 255049, China Institute for Advanced Manufacturing, Shandong University of Technology, Zibo 255049, China 3 Center of Testing and Analysis, Shandong University of Technology, Zibo 255000, China 4 3D Printing Medical Engineering and Technology Center, Shinva Medical Instrument Co., Ltd, Zibo 255086, China 2
Received: 27 May 2020
ABSTRACT
Accepted: 6 August 2020
The evolution of grain boundary character distribution (GBCD) in the CoCrMo alloys processed by SLM and post-heat treatments (aging and solid solution) has been investigated by the electron backscatter diffraction (EBSD) and transmission electron microscope techniques. A high fraction of R3n (n = 1, 2, 3) grain boundaries and the corresponding clusters occur in the solid solution-treated samples at 1150 C, which indicates GBCD optimization is somewhat realized. The coherent and incoherent R3 boundaries were distinguished via the singlesection trace analysis method based on EBSD measurements. R3 boundaries in the SLMed and aged samples were determined as incoherent, while those in the solid solution-treated sample are coherent. Regular e precipitation did not occur in the solid solution-treated samples as in the aged samples. Instead, stacking fault bands associated with coherent R3 twin boundaries are dominant. It suggests that post-heat treatment has a significant influence on the GBCD, especially the R3 grain boundary characteristics.
Springer Science+Business
Media, LLC, part of Springer Nature 2020
Introduction Selective laser melting (SLM) has the advantage of fabricating complex-shaped metal parts while saving time, energy and materials over conventional manufacturing technologies. Nowadays, it has been widely Handling Editor: Sophie Primig.
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https://doi.org/10.1007/s10853-020-05237-7
used in many critical applications such as aerospace, molds, and medical instruments [1–4]. As a candidate material used in the biomedical implants owing to its superior strength, resistance to corrosion, and stress fatigue, CoCrMo alloy has been processed by SLM [5–7]. A fundamental understanding of the microstructure developed during SLM and post-heat
J Mater Sci
treatment has paid more attention to the aim of achieving superior material properties. The existing microstructure analysis [8–12] mainly focuses on grain size and morphology, orientation texture, precipitation behavior, phase distribution, etc. However, the evolution of grain boundary character distribution (GBCD) has not been fully understood. It has been well recognized that low R (B 29) coincident site lattice boundaries (CSLBs) (also called special grain boundary (SB)) typically exhibited immune to grain boundary-related failures [13–15] such a
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