Role of interphases in the deformation mechanisms of an α/ β titanium alloy at 20 K

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 319; pp. 404 - 408
• Main Authors: Ambard, A, Guétaz, L, Louchet, F, Guichard, D
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.12.2001; Elsevier
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; Deformation and plasticity (including yield, ductility, and superplasticity); Dislocations; Exact sciences and technology; Interface; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Metals. Metallurgy; Physics; TEM; Ti–6Al–4V; α/ β titanium alloy; α/ β titanium alloy; Ti–6Al–4V; TEM; Interface; Dislocations; Globular structure; Atomic force microscopy; Beta phase; Ductility; Interphase; Mechanical strength; Alloy-Ti90Al6V4; Experimental study; Titanium base alloys; Dual phase structure; Transmission electron microscopy; Alpha phase; Slip system; Plasticity; Deformation mode; Microstructure
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/S0921-5093(00)02003-7

Two-phase α/ β titanium alloys are used in cryogenic applications owing to their high strength and ductility at such temperatures. The alloy studied here is a Ti–6Al–4V made using a powder metallurgy technique. The α phase exhibits two morphologies; some grains have a globular shape whereas others are lamellar. Five or ten parallel laths form colonies of similarly oriented variants. The deformation mechanisms at 20 K have been studied by Atomic Force Microscopy, post mortem and in situ straining Transmission Electron Microscopy (TEM). The relevant point of the present work is that the nature of α slip systems depends on the α grain morphology. In globular grains, the main slip systems are prismatic as commonly observed in Ti alloys. On the contrary, in lath colonies the basal slip system is activated. This difference is attributed to the presence of the β phase between laths. It is clearly shown that the α/ β interphases play a key role as they act as an α glide system filter. As a consequence, a lath colony behaves as a single grain, which suggests that ductility may be controled by the colony size.