Influence of Zirconium Addition on Creep Behaviour of Nano Crystalline Nickel: A Atomistic Simulation Based Study

Abstract

Objective: The aim of this work is to study the effect of Zr addition (i.e. Ni-3 at. % Zr, 6 at. % Zr, 12 at. % Zr) on structural evaluation and deformation features of nano crystalline (NC) Ni during creep process. In addition, the study of the variation in the effect between randomly distributed Zr and segregated Zr atoms at grain boundary on the creep behaviour of nano crystalline (NC) Ni has been performed. Method: Three dimensional NC Ni specimen with and without Zr addition have been designed using modified Voronoi method. A 14nm x 14nm x 14nm simulation box is taken for performing MD simulation and the simulation box contains 240524 atoms. All the molecular dynamics calculations are performed using a large-scale atomic/molecular massively parallel simulator, LAMMPS with an embedded atom method potential, establish by Wilson and Mendelev applicable for Ni-Zr systems. Result: All the simulated creep curves of NC Ni with and without presence Zr are observed to be consist short primary creep regime, very short secondary creep regime and wide tertiary creep regime. Quasi-uniform deformation mechanism is operative during creep process of NC Ni and Ni-Zr systems. Calculated dislocation density almost becomes nil just after primary regime of creep curve. It is observed that segregated Zr atoms at grain boundaries of NC Ni shows better creep properties compared randomly distributed Zr atoms in NC Ni. Conclusion: The presence of segregated Zr atoms at grain boundaries improves the creep properties of NC Ni.