Length-scale effects in the nucleation of extended dislocations in nanocrystaline Al by molecular-dynamics simulation.

Journal Article · Thu Aug 16 04:00:00 EDT 2001 · Acta Materialia

DOI:https://doi.org/10.1016/S1359-6454(01)00167-7· OSTI ID:943277

Yamakov, V; Wolf, D; Salazar, M; Phillpot, S R; Gleiter, H; Karlsruhe, Forschungszentrum

The nucleation of extended dislocations from the grain boundaries in nanocrystalline aluminum is studied by molecular-dynamics simulation. The length of the stacking fault connecting the two Shockley partials that form the extended dislocation, i.e., the dislocation splitting distance, r{sub split}, depends not only on the stacking-fault energy but also on the resolved nucleation stress. Our simulations for columnar grain microstructures with a grain diameter, d, of up to 70 nm reveal that the magnitude of r{sub split} relative to d represents a critical length scale controlling the low-temperature mechanical behavior of nanocrystalline materials. For r{sub split}>d, the first partials nucleated from the boundaries glide across the grains and become incorporated into the boundaries on the opposite side, leaving behind a grain transected by a stacking fault. By contrast, for r{sub split}<d two Shockley partials connected by a stacking fault are emitted consecutively from the boundary, leading to a deformation microstructure similar to that of coarse-grained aluminum. The mechanical properties of nanocrystalline materials, such as the yield stress, therefore depend critically on the grain size.

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: SC; FOR
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 943277
• Report Number(s): ANL/MSD/JA-38817
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: 14 ; Aug. 16, 2001 Vol. 49; ISSN 1359-6454; ISSN ACMAFD
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM
DISLOCATIONS
GRAIN BOUNDARIES
GRAIN SIZE
MECHANICAL PROPERTIES
MICROSTRUCTURE
MOLECULAR DYNAMICS METHOD
NANOSTRUCTURES
NUCLEATION
STACKING FAULTS