Materials Science and Engineering A 528 (2010) 549–558 Contents lists available at ScienceDirect Materials Science and Engineering A journal homepage: www.elsevier.com/locate/msea Effect of cooling rate on transformation texture and variant selection during  →  transformation in Ti–5Ta–1.8Nb alloy T. Karthikeyan a , Arup Dasgupta a , R. Khatirkar b,1 , S. Saroja a,∗ , I. Samajdar b , M. Vijayalakshmi a a Physical Metallurgy Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu 603 102, India b Dept. of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400 076, India article info Article history: Received 26 February 2010 Received in revised form 27 July 2010 Accepted 20 September 2010 Keywords: Titanium Texture EBSD X-ray diffraction Variant selection abstract The evolution of texture in a cold rolled Ti–5Ta–1.8Nb alloy sheet, during the  →  →  transformation has been studied using EBSD and XRD techniques, for different cooling rates. The sheet exhibited a basal plane type texture upon cold rolling, and a sharp ‘{11 -20}||rolling plane’ transformation texture was inherited after the heat treatment. The microtexture analysis of the lamellar / structure, suggested that this transformation texture arises from the {111}〈110〉 type of high temperature  texture, obeying the Burgers orientation relationship. The strength of the transformation texture was found to sharply increase with decrease in cooling rates, denoting variant selection. Two types of parent  orientations with [1 1 0] parallel to either rolling directions are possible, and among their  product variants, 3 of them are common, and can be preferentially formed at the prior- grain boundaries. The role of grain boundary- in influencing variant selection and the transformation texture for different cooling rates is described in this paper. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Titanium, zirconium and their alloys are known to generally develop crystallographic textures during the various metal form- ing operations. The study of mechanism of texture evolution is useful for optimization of processing parameters, so as to obtain the desired texture and the associated functional properties [1,2]. The low temperature hcp  phase, due to its anisotropic crystal properties and limited slip systems, easily acquires ‘Deformation texture’ during deformation by preferential alignment of certain slip planes with respect to loading geometry. Subsequent anneal- ing of a deformed structure results in nucleation and growth of fresh grains, and could result in a different texture, referred to as the ‘Recrystallization texture’. ‘Transformation texture’ is another mechanism of texture formation, wherein the  phase acquires a specific texture, from the high temperature  (bcc) texture during  →  phase transformation through Burgers orientation ∗ Corresponding author at: Physical Metallurgy Division, Metallurgy and Mate- rials Group, Indira Gandhi Centre for Atomic Research, Materials Characterisation Group, Kalpakkam, Tamil Nadu 603 102, India. Tel.: +91 44 27480306; fax: +91 44 27480202. E-mail address: saroja@igcar.gov.in (S. Saroja). 1 Present address: Department of Metallurgical and Materials Engineering, Visvesvaraya National Institute of Technology, Nagpur-440010, India. relationship [3], (1 1 0)||(0 0 0 1) and (1 1 1)||(1 1 - 2 0) The above orientation relation has been confirmed in many Ti and Zr alloys for both diffusional and martensitic transforma- tions of  → , and has been found to obey during the  →  transformation, as well [4]. There are twelve possible variants for  →  (bcc → hcp) transformation due to crystal symmetry. All the variants are generally expected to form with equal probability. However, the phenomenon of variant selection has been reported in many alloy systems, wherein some variants are formed pref- erentially compared to the other variants, resulting in a strong transformation texture [5–12]. Many factors such as the alloy chemistry, sample geometry, prior deformation of either  or , presence or absence of loading during phase transformation, heat- ing and cooling rate of  →  →  transformation, influence the variant selection effect [6,10,13–16]. Several micro-mechanisms have been proposed to explain the variant selection phenomena during  →  transformation. In the elasticity-based model proposed by Humbert et al. [5,14,16], the variants with minimum elastic strain energy are preferentially nucleated at a grain boundary and grow to be the dominant variant. The elastic strain energy has been calculated based on the Bain dis- tortion associated with the bcc → hcp crystal transformation and the elastic constants representative of the parent  polycrystals. Gey et al. [15] found strong variant selection during  →  trans- formation for a hot rolled Ti6Al4V, and suggested that higher defect 0921-5093/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2010.09.055