Open Access

ARTICLE

Initial Dislocation Structure and Dynamic Dislocation Multiplication In Mo Single Crystals

L. M. Hsiung, D. H. Lassila¹

1 Lawrence Livermore National Laboratory
Chemistry and Materials Science Directorate
L-352, P.O. Box 808
Livermore, CA 94551-9900
hsiung1@llnl.gov

Computer Modeling in Engineering & Sciences 2002, 3(2), 185-191. https://doi.org/10.3970/cmes.2002.003.185

Abstract

Initial dislocation structures in as-annealed high-purity Mo single crystals, and deformation substructures of the crystals compressed at room temperature under different strain rates have been examined and studied in order to elucidate the physical mechanisms of dislocation multiplication and motion in the early stages of plastic deformation. The initial dislocation density was measured to be in a range of 10⁶ ~ 10⁷ cm⁻². More importantly numerous grown-in superjogs were observed along screw dislocation lines. After testing in compression, dislocation density (mainly screw dislocations) increased to 10⁷ ~ 10⁸ cm⁻². Besides, the formation of dislocation dipoles (debris) due to the nonconservative motion of jogged screw dislocations was found to be dependent of the strain rates. While little dislocation dipoles (debris) were found in the crystal tested quasistatically(10⁻³ s⁻¹), more cusps along screw dislocation lines and numerous dislocationdipoles (debris) were observed in the crystal compressed under the strain rate of 1s⁻¹. Physical mechanisms for dislocation multiplication as well as dipole formation from jogged screw dislocations under different strain rate conditions are accordingly proposed and discussed.

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