Understanding the anisotropic mechanical behaviour and dislocation analysis of additively manufactured CoCr alloy: insight from atomistic simulation

A molecular dynamics simulation based novel approach is utilized for studying the evolution of atomic arrangement, phases, and dislocations during layer by layer deposition of CoCr, and tensile properties of CoCr deposit upon additive manufacturing. The CoCr alloy is used for dental crowns and prosthetics due to its biocompatibility, strength and corrosion resistance properties. The current work focuses on the diffusion of atoms at the interface of layers interface during deposition and diffusivity is estimated to be 1.2 × 10^–12 m²/s. The simulations suggest that amorphous phase fraction decreases from 78 to 12% as cooling rate decreases from 70 to 2.3 K/ps. The maximum tensile strength at a strain rate of 10⁹/s is predicted to be ~ 4200 MPa and ~ 4000 MPa along the layer deposition direction and build direction, respectively. Further dislocation analysis reveals the generation of several type of dislocations, i.e. Shockley, Hirth and Stair rod, upon deformation of the samples under tensile loading. The Hirth and Stair rod dislocation are considered barriers to the dislocation movement during deformation.