Grain boundary character distribution in the CoCrMo alloy processed by selective laser melting and post-heat treatment

Abstract

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 Σ3n (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 Σ3 boundaries were distinguished via the single-section trace analysis method based on EBSD measurements. Σ3 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 Σ3 twin boundaries are dominant. It suggests that post-heat treatment has a significant influence on the GBCD, especially the Σ3 grain boundary characteristics.