Texture and Mechanical Behavior of Zircaloy-2 Rolled at Different Temperatures Sunkulp Goel, Nachiket Keskar, R. Jayaganthan, I.V. Singh, D. Srivastava, G.K. Dey, S.K. Jha, and N. Saibaba (Submitted July 3, 2014; in revised form October 2, 2014; published online December 2, 2014) Zircaloy-2 was deformed by cryorolling (CR) and room-temperature rolling (RTR) with different true strains, and the effects of true strains on microstructural characteristics, texture, and mechanical properties of the alloy were investigated in the current study. The alloy was subjected to rolling at liquid nitrogen temperature and room temperature with the maximum true strain of 1.89 after the initial heat treatment of the alloy at 800 °C in inert atmosphere followed by quenching in mercury. The hardness and tensile properties of the CR, RTR, and annealed alloy upon rolling were systematically measured in rolling and transverse directions. The tensile strengths were found to be 891 and 679 MPa, while hardness values were found to be 282 and 269 VHN for the CR and RTR alloys, in the rolling direction, respectively. Texture results showed the activation of basal slip at higher strains in RTR zircaloy-2. In CR zircaloy-2, only activation of prism slip was observed. Grain refinement, substructures, and texture in the deformed alloy contribute to the improved mechanical properties observed in the current study. Keywords mechanical properties, rolling, texture, ultrafine grains 1. Introduction Zircaloy-2 is used as pressure tubes and cladding materials in nuclear reactors for the power generations owing to their excellent mechanical properties such as strength, fatigue, and corrosion resistance (Ref 1-4). The HCP structure of this alloy significantly affects its deformation behavior due to the forma- tion of different textures during thermo-mechanical processing, resulting in anisotropic behavior in mechanical properties. The lack of slip systems and twinning plays an important role in the plastic deformation of the HCP materials. Twinning causes nonreversal reorientation of c axis due to which strong crystallographic texture is formed, imparting anisotropy to hcp material (Ref 5-7). In general, texture in the materials is formed during various processing types such as casting, welding, thermomechanical processing, and even heat treatment. At room temperature and above, both slip and twinning affect the plastic deformation of zircaloy-2. Low c/a ratio causes slip to be more on 10 10   plane with 1 210   direction. In {0002} plane, slip is rarely observed, but cold working makes the prism slip strain hardened and causes the activation of basal slip. Von Mises criteria of plastic deformation and large plasticity of zircaloy-2 are validated by pyramidal slip. It is observed in first 10 11   plane and second order in 11 22   plane along 11 23   (c + a) directions as reported in the literature (Ref 6-8). When ÔcÕ axis is parallel to normal direction, prism slip is not possible. Therefore, the grains in hcp materials can only deform either by Æc+aæ pyramidal slip or by 11 22   1123     compressive twinning. It was reported that at room temperature, Æc+aæ pyramidal slip is easier to activate than 11 22   1123     compressive twinning (Ref 9). At large strain greater than 0.5, basal slip gets activated at room temperature (Ref 10). Twinning is one of the deformation modes in hcp-structured materials as it may provide favorable planes for further slip. Twinning modes depend on the type of resultant load which the crystal experiences, viz., whether it is tensile or compressive. In tensile loading along c axis, 10 12   1011     twin gets activated, and 11 21   1126     twin gets activated less often. During compressive loading along c axis, 11 22   1123     twins are active, while at high temperature, 10 11   1012     twin is observed (Ref 6-8).The deformation modes which are observed at liquid nitrogen temperature are prismatic slip, tensile twinning 10 12   1011     , 11 21   1126     and com- pressive twinning 11 22   1123     (Ref 11). Microstructure of zircaloy-2 after deformation exhibits fragmented and nonfragmented types of grains. There is also formation of twins after deformation of this alloy. Realignment and annihilation of dislocation and formation of high angle grain boundary are responsible for fragmentation of grains. At the same time, plastic deformation leads to misorientation of prior twins causing annihilation of twins (Ref 12). Grains with near-basal orientation {0002} are nonfragmenting as they are elastically harder (Ref 13). Zirconium alloy rolled between 790 and 850 °C shows that most of the grains in basal plane are inclined toward transverse direction (Ref 14, 15). During rolling of Zircaloy-2, the sheet is elongated toward the rolling direction, and a small spread of sheet is seen in the transverse direction. The compressive force exerted mainly in the normal direction but very little in the transverse direction due to which Sunkulp Goel and R. Jayaganthan, Department of Metallurgical and Materials Engineering & Centre of Nanotechnology, IIT Roorkee, Roorkee 247667, India; Nachiket Keskar, D.Srivastava, and G.K. Dey, Materials Science Division, Bhabha Atomic Research Center, Mumbai 40085, India; I.V.Singh, Department of Mechanical and Industrial Engineering, IIT Roorkee, Roorkee 247667, India; and S.K. Jha and N. Saibaba, Nuclear Fuel Complex Limited, Hyderabad 501301, India. Contact e-mail: rjayafmt@iitr.ernet.in. JMEPEG (2015) 24:618–625 ÓASM International DOI: 10.1007/s11665-014-1315-y 1059-9495/$19.00 618—Volume 24(2) February 2015 Journal of Materials Engineering and Performance