Atomic-scale modeling of dislocations and related properties in the hexagonal-close-packed metals |
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Authors: | D J Bacon V Vitek |
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Affiliation: | (1) Materials Science and Engineering, Department of Engineering, The University of Liverpool, L69 3GH Liverpool, United Kingdom;(2) the Department of Materials Science and Engineering, University of Pennsylvania, 19104 Philadelphia, PA |
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Abstract: | Metals with the hcp crystal structure have a wide variety of mechanical and physical properties, and understanding the links
between atomic processes, microstructure, and properties can open the way for new applications. Computer modeling can provide
much of the information required. This article reviews recent progress in atomic-scale computer simulation in three important
areas. The first is the core structure of dislocations responsible for the primary slip modes, where modeling has revealed
the variety of core states that can arise in pure, elemental metals and ordered alloys. While most research has successfully
employed many-body, central-force interatomic potentials, they are inadequate for metals which have an unfilled d-electron
band, such as α-Ti and α-Zr, and the resulting noncentral character of the atomic bonding is shown to have subtle yet significant effects on dislocation
properties. Deformation twinning is an important process in plasticity of the hcp metals, and modeling has been used to investigate
the factors that control the structure and mobility of twinning dislocations. Furthermore, simulation shows that twinning
dislocations are actually generated, in some cases, following the interaction of crystal dislocations with twin boundaries;
this can lead to the very mobile boundaries observed experimentally. The final area concerns the nature and properties of
the defects created by radiation damage. Computer simulation has been used to determine the number and arrangement of defects
produced in primary, displacement-cascade damage in several hcp metals. The number is similar to that found in cubic metals
and is considerably smaller than that expected from earlier models. Many self-interstitial atoms cluster in cascades to form
highly glissile dislocation loops, and, so, contribute to two-dimensional material transport in damage evolution.
This article is based on a presentation made in the symposium entitled “Defect Properties and Mechanical Behavior of HCP Metals
and Alloys” at the TMS Annual Meeting, February 11–15, 2001, in New Orleans, Louisiana, under the auspices of the following
ASM committees: Materials Science Critical Technology Sector, Structural Materials Division, Electronic, Magnetic & Photonic
Materials Division, Chemistry & Physics of Materials Committee, Joint Nuclear Materials Committee, and Titanium Committee. |
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