Simulation of an edge source in the Cu-Ni multilayer system

Journal Article · Fri Oct 22 04:00:00 EDT 1999 · Scripta Materialia

DOI:https://doi.org/10.1016/S1359-6462(99)00257-2· OSTI ID:20001709

Rao, S I; Hazzledine, P M

Metallic multilayered structures are known to possess unusual physical and mechanical properties. At small layer wavelengths ({approximately}10--50nm), multilayered structures are reported to have significant enhancements in their yield and fracture strengths. Yield strength enhancements in metallic multilayered structures have been observed in a large number of systems. Theoretical models predicting the yield strength of multilayered systems can be classified into two categories: (1) Models based on the Orowan strengthening mechanism and (2) Hall-Petch strengthening type of models. The purpose of this paper is to test the Matthews and Blakslee theory in a very thin layer by simulating a dislocation source in Ni atomistically. In this manuscript, 3-dimensional (3-D) atomistic simulations incorporating Green's function boundary conditions (GFBC's) are used to calculate the bowing of a short edge segment (Burgers' vector = 1/2[110], line direction = [1 {bar 1}2]) of length 8 nm under an applied shear stress in FCC Ni. Atomistic simulation results on the bowing of the source is shown to be in excellent agreement with anisotropic elasticity predictions even at these short segment lengths. Elasticity calculations are then used to show that for all wavelengths and volume fracture of Ni in the Cu-Ni multilayered system, coherency stresses present in Ni are almost identical to the stresses required for activating a source. These results are equally applicable for activation of sources in the softer Cu layer. This indicates that the Orowan mechanism of yielding occurs at almost no applied stress and the yield strengthening observed in the Cu-Ni multilayered system is a result of either the interface barrier to dislocation motion or the effect of the coherency stress in the disfavored layer.

• Research Organization: Wright Lab., Wright-Patterson AFB, OH (US)
• OSTI ID: 20001709
• Journal Information: Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 10 Vol. 41; ISSN SCMAF7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COMPOSITE MATERIALS
COPPER ALLOYS
DISLOCATIONS
GREEN FUNCTION
LAYERS
MICROSTRUCTURE
NICKEL ALLOYS
SIMULATION
STRESSES
YIELD STRENGTH