Contents lists available at ScienceDirect Materials Today Communications journal homepage: www.elsevier.com/locate/mtcomm The role of initial α-phase orientation on tensile and strain hardening behavior of Ti-6Al-4V alloy P. Ahmadian ⁎ , S.M. Abbasi, M. Morakabati Metallic Materials Research Center, Malek Ashtar University of Technology, Tehran, Iran ARTICLE INFO Keywords: Ti6Al4V Microstructure Texture Strain hardening Initial orientation Hard/soft grain ABSTRACT The effect of initial α-phase orientation on mechanical properties and strain hardening behavior of Ti-6Al–4V alloy was investigated. Two samples have been unidirectional rolled at 950 and 800 °C. Third sample was cross rolled at 800 °C. subsequently all the samples were annealed at 960 °C for 1 h and slowly cooled at furnace to obtain fully equiaxed microstructure with different initial texture. Strain hardening behavior of samples was calculated by phenomenological Kocks-Mecking approach ( = θ Gvsε / dσ dε p ). Results showed that during plastic deformation, prismatic texture resulted in low value in yield stress and excellent work hardening capacity. With decreasing in unidirectional rolling temperature from 950 to 800 °C, anisotropy in yield stress and work hard- ening capacity is increased as a result of basal and prismatic texture while ductility has not been significantly influenced. In the case of cross rolling, anisotropy is significantly mitigated as a result of basal texture aug- mentation while ductility is decreased which is related to hard grain adjacent to soft one. 1. Introduction Ti-6Al–4 V (Ti64) is the workhorse alloy of titanium industry con- sisting two phase structures i.e. a predominant α-phase (HCP structure) with retained β-phase (BCC structure) distributed along its grain boundary. It possesses an exclusive combination of high specific strength (i.e. strength/weight ratio), excellent corrosion resistance, good hot formability and high creep resistance up to 425 °C. Thus it is used in aerospace, petroleum, biomedical industries [1–7]. Despite the widespread application of Ti64 alloy, its cold workability is limited [8]. Numerous studies [9–13] have been carried out on the microstructure and texture evolution of Ti64 alloy during thermo-mechanical process. Deformation behavior of Ti64 alloy is controlled by active deformation modes of dominant α-phase while β-phase contribution is negligible [14]. Major slip systems for α-pahse in Ti alloys is basal ( 1120 {0002} ), prismatic ( 1120 {1010} ) and pyramidal ( 1120 {1011} , 1123 {1122} ) [15–17]. Critical resolved shear stress for → + → c a type slip system is much higher than → a type one [18]. It was mentioned that most failure in α+β titanium alloys is connected to high plastic anisotropy asso- ciated with hard/soft grain interaction [19]. Soft oriented grains are oriented along → a type slip system while hard oriented grains are not [20]. During plastic deformation, dislocation-pile up is enhanced in hard/soft grain interface. Texture development in α-phase is a function of rolling temperature and rolling mode [21]. Generally speaking, it is conceivable to develop T (transverse), B/T (basal/transverse) and B (basal) texture in α+β titanium alloys especially in Ti64 during thermo-mechanical process. Wanger et al. [22] demonstrated that subsequent annealing has no significant effect on deformation texture of two phase titanium alloys. Correlation between mechanical proper- ties and texture components in Ti64 alloy a very thought-provoking field of study. A practical way for improving deep drawability in Ti64 sheet is to develop basal texture by fully cross rolling process [23]. Song et al. [24] showed that decreasing cross rolling temperature develop ND//(1120) fiber-texture in Ti64 which is associated with decreasing anisotropy in yield stress. However the effect of grain orientation on work hardening capacity of hexagonal metals especially Ti64 has not been correlated clearly. Afrin et al. [25] indicated that work hardening capacity of magnesium alloy is inversely proportional to strain hard- ening rate (θ=dσ/dε). Lower initial θ value resulted in lower YS value and higher work hardening capacity. In their study, work hardening capacity is defined by using a normalized parameter, i.e. H c and dif- ferent stage of strain hardening is illustrated by using Kocks-Mecking type plot. H c is defined in the following equation: = − H σ σ σ c UTS YS YS (1) Where σ UTS and σ YS are ultimate tensile strength and yield stress re- spectively. In the phenomenological Kocks-Mecking approach, work hardening is governed by the competition between multiplication and annihilation rate of dislocations [26]. During plastic deformation, http://dx.doi.org/10.1016/j.mtcomm.2017.10.018 Received 14 October 2017; Accepted 30 October 2017 ⁎ Corresponding author. E-mail address: pahmadian7@gmail.com (P. Ahmadian). Materials Today Communications 13 (2017) 332–345 Available online 31 October 2017 2352-4928/ © 2017 Published by Elsevier Ltd. MARK