The thermal stability of and nature of damage in Ti alloys subject to high-strain-rate deformation

• Published in: Philosophical magazine (Abingdon, England) Vol. 84; no. 32; pp. 3411 - 3418
• Main Authors: Wu †, Xinhua, Zakaria, M., Loretto, M. H.
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis Group 11.11.2004; Taylor and Francis
• Subjects: Condensed matter: structure, mechanical and thermal properties; Defects and impurities in crystals; microstructure; Deformation and plasticity (including yield, ductility, and superplasticity); Exact sciences and technology; Linear defects: dislocations, disclinations; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Physics; Structure of solids and liquids; crystallography; Annealing; Inorganic compounds; Deformation; Vanadium alloys; Ternary alloys; Experimental study; Thermal stability; Multi-element alloys; Dislocations; Tin alloys; Titanium alloys; Transmission electron microscopy; Aluminium alloys; Damage; Molybdenum alloys; Transition element alloys; Kikuchi lines
• ISSN: 1478-6435; 1478-6443
• DOI: 10.1080/14786430412331284450

Samples of Ti-6 wt% Al-4 wt% V and Timet 550 (Ti-4 wt% Al-4 wt% Mo-2 wt% Sn-0.5 wt% Si wt%), which have been deformed at a strain rate of 5 s −1 , were annealed after thinning so that the visibility of dislocations in transmission electron microscopy could be compared before and after annealing. It has been found that imaging with g = 0002 produces clear images of dislocations before and after annealing, but that imaging with other diffracting vectors gives reasonable dislocation images only after annealing to at least 700°C. The sharpness of Kikuchi lines in diffraction patterns obtained from fully annealed samples, deformed at 10 −1 and 5 s −1 , has been examined. The lines are sharp for all planes in the fully annealed samples, but become more diffuse in samples deformed at 10 −1  s −1 . However, in samples deformed at 5 s −1 the Kikuchi lines from (0002) planes are sharp but the lines from all other planes are diffuse. These observations are interpreted in terms of the presence of a high density of defects, which do not distort the elastically strong (0002) planes as significantly as they distort all other planes. These observations are discussed with respect to the recent claim that a particular Ti alloy deforms by a mechanism that does not involve dislocations.