Microstructure and Tensile Properties of Co-Cr Alloy Formed by Laser Selective Melting

Co-Cr alloy was prepared by laser selective melting. The microstructure, crystal structure and tensile properties of the Co-Cr alloy in different directions (perpendicular and parallel to forming direction) were studied. The tensile properties anisotropy was analyzed according to microstructure characteristics. The results show that the microstructure of the CoCr alloy was anisotropic. There was a fish-scale trace on the face parallel to the forming direction, and the crystal had a columnar grain structure. There was a laser melting trace on the face perpendicular to the forming direction, and the crystal had a fine cellular honeycomb arranged equiaxial grain structure. Compared with those on the face parallel to forming direction, the proportion of grain boundaries at small angles and the mean nuclear mismatch on the face perpendicular to forming direction were large,the Schmid factor was small, the tensile strength and yield strength increased by 13.74% and 16.55%, respectively, and the percentage elongation after fracture decreased by 15.64%. The tensile properties in direction perpendicular to forming showed high strength and low plasticity. The anisotropy of tensile properties of Co-Cr alloy was mainly attributed to different fine grain strengthening effect and dislocation density in different directions, and the tensile fracture mechanism in direction parallel and perpendicular to forming direction was quasi-cleavage fracture.