skip to main content

Title: Atomistic tensile deformation mechanisms of Fe with gradient nano-grained structure

Large-scale molecular dynamics (MD) simulations have been performed to investigate the tensile properties and the related atomistic deformation mechanisms of the gradient nano-grained (GNG) structure of bcc Fe (gradient grains with d from 25 nm to 105 nm), and comparisons were made with the uniform nano-grained (NG) structure of bcc Fe (grains with d = 25 nm). The grain size gradient in the nano-scale converts the applied uniaxial stress to multi-axial stresses and promotes the dislocation behaviors in the GNG structure, which results in extra hardening and flow strength. Thus, the GNG structure shows slightly higher flow stress at the early plastic deformation stage when compared to the uniform NG structure (even with smaller grain size). In the GNG structure, the dominant deformation mechanisms are closely related to the grain sizes. For grains with d = 25 nm, the deformation mechanisms are dominated by GB migration, grain rotation and grain coalescence although a few dislocations are observed. For grains with d = 54 nm, dislocation nucleation, propagation and formation of dislocation wall near GBs are observed. Moreover, formation of dislocation wall and dislocation pile-up near GBs are observed for grains with d = 105 nm, which is the first observationmore » by MD simulations to our best knowledge. The strain compatibility among different layers with various grain sizes in the GNG structure should promote the dislocation behaviors and the flow stress of the whole structure, and the present results should provide insights to design the microstructures for developing strong-and-ductile metals.« less
Authors:
; ;  [1]
  1. State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Science, No.15, North 4th Ring, West Road, Beijing 100190 (China)
Publication Date:
OSTI Identifier:
22492300
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Advances; Journal Volume: 5; Journal Issue: 8; Other Information: (c) 2015 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BCC LATTICES; COALESCENCE; COMPARATIVE EVALUATIONS; DEFORMATION; DISLOCATIONS; FLOW STRESS; GRAIN SIZE; HARDENING; LAYERS; METALS; MOLECULAR DYNAMICS METHOD; NANOSTRUCTURES; NUCLEATION; PLASTICITY; ROTATION; STRAINS; TENSILE PROPERTIES