1 Temperature dependence of work hardening in sparsely twinning zirconium Jaiveer Singh 1 , S. Mahesh 2 , Shomic Roy 1,3 , Gulshan Kumar 1 , D. Srivastava 4 , G. K. Dey 4 , N. Saibaba 5 and I. Samajdar 1 1 Department of Metallurgical Engineering & Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai-400 076, India 2 Departments of Aerospace Engineering, Indian Institute of Technology Madras, Chennai-600 036, India 3 Scientific Services, Tata Steel Limited, Jamshedpur-831 001, India 4 Materials Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085, India 5 Nuclear Fuel Complex, Hyderabad-500 062, India Abstract Fully recrystallized commercial Zirconium plates were subjected to uniaxial tension. Tests were conducted at different temperatures (123 K - 623 K) and along two plate directions. Both directions were nominally unfavorable for deformation twinning. The effect of the working temperature on crystallographic texture and in-grain misorientation development was insignificant. However, systematic variation in work hardening and in the area fraction and morphology of deformation twins was observed with temperature. At all temperatures, twinning was associated with significant near boundary mesoscopic shear, suggesting a possible linkage with twin nucleation. A binary tree based model of the polycrystal, which explicitly accounts for grain boundary accommodation and implements the phenomenological extended Voce hardening law, was implemented. This model could capture the measured stress-strain response and twin volume fractions accurately. Interestingly, slip and twin system hardness evolution permitted multiplicative decomposition into temperature-dependent, and accumulated strain-dependent parts. Furthermore, under conditions of relatively limited deformation twinning, the work hardening of the slip and twin systems followed two phenomenological laws proposed in the literature for non-twinning single-phase face centered cubic materials. Keywords: Zirconium, Work hardening, Twinning, Polycrystal Plasticity, Temperature, Microstructure.