Tuning the strength and ductility balance of a Co32Cr36Ni32 medium entropy alloy fabricated by selective laser melting: Effect of segregations along grain boundaries

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2022-04, Vol.840, p.142923, Article 142923
• Main Authors: Pan, Cunliang, Li, Xiaoqiang, Luo, Hao, Kosiba, Konrad, Qu, Shengguan, Yang, Chao, Zhu, Dezhi, Zhang, Cong
• Format: Article
• Language: English
• Subjects: Additive manufacturing; Alloys; Co32Cr36Ni32 alloy; CoCrNi medium Entropy alloy; Crack sensitivity; Ductility; Elongation; Entropy; Grain boundaries; Grain boundary segregation; Hot cracks; Laser beam melting; Mechanical properties; Medium entropy alloys; Rapid prototyping; Room temperature; Segregations; Selective laser melting; Solidification; Titanium carbide; Ultimate tensile strength; Yield strength
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2022.142923

Dense Co32Cr36Ni32-3 wt% TiC medium entropy alloy parts were successfully fabricated via selective laser melting (SLM) and they showed high strength and good ductility. Due to the addition of micro-TiC particles, which was partially dissolved during SLM processing, C diffused into the Co32Cr36Ni32-based melt and led to the formation of nano-sized TiC and Cr23C6-segregations along the grain boundaries of the solidified microstructure. The segregations showed a coherent relationship with the matrix and reinforced it. Owing to their formation, the grain boundary energy was reduced. Thus, the liquid film present between columnar grains during solidification was consumed which eventually manifested in the reduction of the hot crack sensitivity (HCS). The additively manufactured material showed excellent mechanical properties readily characterized by ultimate tensile strength (UTS) of 1340 MPa, yield strength (YS) of 1020 MPa, and elongation (El) of 15.6% at room temperature, respectively.