Investigation of deformation degree and initial forming temperature dependences of microstructure in hot ring rolling of TA15 titanium alloy by multi-scale simulations

Hot ring rolling is a preferred technology for manufacturing high-quality titanium alloy rings. During the process, the material undergoes complex microstructure evolution which determines the mechanical properties of the rolled ring. In this study, an internal state variable microstructure model for the hot working of TA15 titanium alloy is implemented into the 3D-FE model of hot ring rolling process under ABAQUS environment to realize multi-scale simulation of the process. Then the effects of deformation degree and initial forming temperature on the microstructure of TA15 titanium alloy in hot ring rolling are investigated numerically. The results show that: (1) with increasing deformation degree, the volume fraction and grain size of primary alpha phase in the ring both decrease, and the primary a phase distribution becomes more nonuniform while the primary alpha grain size distribution becomes more uniform; (2) with increasing initial forming temperature, the volume fraction and grain size of primary alpha phase both decrease, and the uniformity of primary alpha phase distribution gets better first and then worse while the uniformity of primary alpha grain size distribution gets better; and (3) in order to obtain uniform distributions of both primary alpha phase and grain size, an optimum process condition for hot ring rolling of TA15 titanium alloy is suggested to be the deformation degree of 0.25-0.35 and the initial forming temperature of 930-940 degrees C. The results can serve as a guide to the microstructure control, blank size design and processing parameter optimization for hot ring rolling of titanium alloy. (c) 2012 Elsevier B.V. All rights reserved.