The structure of 〈c + a〉 type dislocation loops in magnesium

• Published in: Philosophical magazine letters 2014-06, Vol.94 (6), p.377-386
• Main Authors: Geng, J., Chisholm, M.F., Mishra, R.K., Kumar, K.S.
• Format: Article
• Language: English
• Subjects: Close packed lattices; Cold working, work hardening; annealing, quenching, tempering, recovery, and recrystallization; textures; Compressed; compression; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Defects and impurities in crystals; microstructure; deformation; Deformation and plasticity (including yield, ductility, and superplasticity); Density; Dislocation loops; dislocations; Exact sciences and technology; Magnesium; magnesium single crystal; Materials science; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Physics; Plastic strain; Scanning electron microscopy; Stacking faults and other planar or extended defects; Structure of solids and liquids; crystallography; Transmission electron microscopy; Treatment of materials and its effects on microstructure and properties
• ISSN: 0950-0839; 1362-3036
• DOI: 10.1080/09500839.2014.916423

Mg (hcp) single crystals exhibit an unusually high work-hardening rate when compressed along the c-axis at room temperature. Post-deformation investigation using bright-field and weak-beam dark-field techniques in a transmission electron microscope (TEM) and by high-angle annular dark-field imaging (HAADF) using a scanning transmission electron microscope confirms the presence of sessile c + a type dislocation loops on the basal plane whose density increases with increasing plastic strain; their presence is thought to account at least in part for the high work-hardening rate. These loops appear to be often arranged as rows along the 〈10-10〉 directions, are hexagonal in shape with their sides coinciding with the 〈10-10〉, are faulted and are composed of two 1/6〈20-23〉 type partials loops bounding a basal stacking fault. Their presence is attributed to the decomposition reaction 1/3[2-1-13] → 1/6[2-203] + SF (0001) + 1/6[20-23].