Grain-boundary diffusion creep in nanocrystalline palladium by molecular-dynamics simulation.
Molecular-dynamics (MD) simulations of fully three-dimensional (3D), model nanocrystalline face-centered cubic metal microstructures are used to study grain-boundary (GB) diffusion creep, one mechanism considered to contribute to the deformation of nanocrystalline materials. To overcome the well-known limitations associated with the relatively short time interval used in our MD simulation (typically <10{sup -8} s), our simulations are performed at elevated temperatures where the distinct effects of GB diffusion are clearly identifiable. In order to prevent grain growth and thus to enable steady-state diffusion creep to be observed, our input microstructures were tailored to (1) have a uniform grain shape and a uniform grain size of nm dimensions and (2) contain only high-energy GBs which are known to exhibit rather fast, liquid-like self-diffusion. Our simulations reveal that under relatively high tensile stresses these microstructures, indeed, exhibit steady-state diffusion creep that is homogeneous, with a strain rate that agrees quantitatively with that given by the Coble-creep formula. The grain-size scaling of the Coble creep is found to decrease from d{sup -3} to d{sup -2} when the grain diameter becomes of the order of the GB width. For the first time a direct observation of the grain-boundary sliding as an accommodation mechanism for the Coble creep, known as Lifshitz sliding, is reported.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- SC
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 949333
- Report Number(s):
- ANL/MSD/JA-40068
- Journal Information:
- Acta Materialia, Journal Name: Acta Materialia Journal Issue: 1 ; Jan. 8, 2002 Vol. 50; ISSN 1359-6454; ISSN ACMAFD
- Country of Publication:
- United States
- Language:
- ENGLISH
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Molecular-dynamics simulation of grain-boundary diffusion creep.
ATOMISTIC SIMULATIONS OF DIFFUSIONAL CREEP IN A NANOCRYSTALLINE BODY-CENTERED CUBIC MATERIAL