The Effect of Porosity on Creep Behavior of Nickel Single Crystal: An Atomistic Simulation Based Study

Abstract

Tensile creep behavior of single crystal Ni with and without presence of porosity in various atom percent (i.e. 0, 10 and 18 at. %) has been studied using a molecular dynamic (MD) simulation with an embedded atom method (EAM) potential. A10 nm x 10 nm x 10 nm cubic simulation box is taken for performing MD simulation which contained 92597 atoms for 0 at % porosity, 83387 atoms for 10 at % porosity and 75948 atoms for 18 at % porosity. MD simulation of creep for this single crystal has been carried out at 907 oC, 917 oC, 927 oC and 936 oC temperatures and constant 1.0 GPa stress. The increase in porosity has strong influence on creep behaviour as revealed from the simulated creep curves. Centro symmetry parameter (CSP) evaluation, common neighbour analysis (CNA), Voronoi clusters (VCs) analysis, radial distribution function (RDF) plots study and Wigner Seitz defect analysis have been carried out to investigate structural evolution of the specimen during creep. It is evident that amorphization during creep deformation process become faster and intensified as atomic fraction of porosity increases Simulated creep curve with corresponding 3-D snapshots at 907OC temperature and 1.0 GPa stress for 18 at. % porosity in single crystal Ni specimen is represented in Figure. 1. It is found that nano-materials have faster diffusibility of the atoms for 18 at. % porosity of single crystal Ni specimen than 0 and 10 at. % porosity. The effect of porosity variation (0 to 18 at. % porosity) is prominent on creep process. The creep curves of specimen are observed to be shifted towards higher creep strain during secondary part of creep with increase of porosity from 0 to 18 at. %..