Abstract
Here we report on a molecular dynamics simulation of the atomic volume distribution in fcc copper with moving partial dislocations 1/6 〈112〉 {111}. The simulation shows that the leading and trailing partial dislocations surrounding a stacking fault move via local fcc→hcp and hcp→fcc transformations and that a fcc–hcp transition zone exists in which the atomic volume is larger than that in the perfect close-packed structure. The excess volume is five to seven percent, which compares with volume jumps on melting. The simulation results agree with experimental data showing that the nucleation of dislocations is preceded by the formation of regions with an excess atomic volume.
Highlights
Amorphous and crystalline materials are essentially different in atomic structure, and plastic deformation in them nucleates and evolves differently
Our molecular dynamics study of mechanically loaded copper shows that the use of an extended indenter in simulations allows one to generate isolated stacking faults and to trace their motion in model crystallites
Our study is the first to demonstrate the existence of a transition zone which borders this type of defects and always features an excess atomic volume responsible for local lattice instability
Summary
Amorphous and crystalline materials are essentially different in atomic structure, and plastic deformation in them nucleates and evolves differently. In mechanically loaded fcc metals, specific local transformations corresponding to fcc–hcp transitions were observed[20,21] Such local transformations were considered as certain protodefects responsible for classical structural defects like partial dislocations, stacking faults, etc., and their mechanisms were studied[20,21]. In this connection, it is of interest to investigate how the excess volume contributes to the incipient plasticity in crystalline materials and how this contribution correlates with that in amorphous materials
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