Molecular Dynamics Simulation of Mechanical Properties of Different Grain Sizes and Gradient-Nano-Grain Structure of Copper-Silver Alloy

Abstract

In this work the mechanical properties and fracture behaviors of the structures with different grain sizes and Gradient-Nano-Grain (GNG) of Cu50Ag50 alloy were individually investigated under the uniaxial tensile stress Molecular dynamics (MD) simulation with Finnis-Sinclair (FS) potential was adopted in numerical simulation Grain sizes of 16 97 nm 12 nm and 2 68 nm were selected in the samples with the mean grain sizes and GNG structure Common neighbor analysis (CNA) and radial distribution function (RDF) method were employed for structure identification Pre-cracked Cu50Ag50 alloy models under uniaxial tensile were also considered to investigate the crack growth and propagation Simulation results indicate that the maximum strength and the inverse Hall-Petch (H-P) relationship can be observed at the grain size of 12 nm and the ultimate tensile strength (UTS) is as high as 1 84 GPa The UTS decreases with the decrease of the mean grain sizes while the ductility increases and the plastic deformation become more uniform Moreover for GNG structure stress induced phase transformation can be found during uniaxial tensile test The initial crystalline structure transforms into a high proportion of amorphous structure and the grain boundaries between the initial grains disappear The effect of GNG structure on mechanical properties is not significant Moreover it was found that the crack tip exhibits blunting due to plastic deformation after the action of uniaxial tensile stress Therefore the Cu50Ag50 alloy shows good resistance of crack propagation than other brittle materials

Date of Award	2019
Original language	English
Supervisor	Tei-Chen Chen (Supervisor)