Analysis of high-speed-deformation-induced defect structures using heterogeneity parameter of dislocation distribution

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 350; no. 1; pp. 63 - 69
• Main Author: Kiritani, Michio
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 15-06-2003; Elsevier
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; Defects and impurities in crystals; microstructure; Deformation and plasticity (including yield, ductility, and superplasticity); Deformation-induced dislocations; Exact sciences and technology; Heterogeneity parameter of dislocation distribution; High-speed plastic deformation; Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, epr, nmr, etc.); Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Metals. Metallurgy; Physics; Structure of solids and liquids; crystallography; Vacancy clusters; Vacancy clusters; Deformation-induced dislocations; Heterogeneity parameter of dislocation distribution; High-speed plastic deformation; Compression; High strain; Dislocation structure; Vacancy cluster; Plastic deformation; Random distribution; Transition elements; High speed; Defect structure; Defect formation; Strain rate
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/S0921-5093(02)00695-0

An appropriate parameter, named the heterogeneity parameter, is introduced for quantitatively representing the nature of distribution of deformation-induced dislocations. The parameter assumes values ranging from 0 to 1, the extremes corresponding to homogeneous and heterogeneous distribution, respectively. The parameter can represent distribution of intermediate nature, typified by stochastically random distribution which has a heterogeneity parameter of about 0.35. Heterogeneity parameter is used to analyze variation in dislocation structure in many kinds of metals for a wide range of deformation speed from 10
−2 to 10
7 s
−1 in strain rate. The parameter has large values at slow-speed-deformation, and decreases with increasing strain rate, reaching the level of random distribution at a deformation speed of around 10
4 s
−1. Above this strain rate, formation of vacancy clusters increases remarkably. On the basis of these results of analysis, occurrence of dislocation-free plastic deformation during high-speed-deformation is proposed.