Unified constitutive modelling for two-phase lamellar titanium alloys at hot forming conditions
School of Mechanical Engineering, University of Science and Technology Beijing, Beijing
2 Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, UK
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Accepted: 4 September 2016
In this paper, a set of mechanism based unified viscoplastic constitutive equations have been established for two-phase titanium alloys with initial lamellar microstructure, which models the softening mechanisms of the alloys in hot forming conditions. The dislocation density, rotation and globularization of lamellar α-phase and their effects on flow behaviour can also be modelled. The values of material constants in the equation set have been calibrated, according to stress-strain curves and globularization fractions of lamellar α-phase obtained from compression tests at a range of temperatures and strain rates, using a genetic algorithm (GA) based optimisation method. Based on the determined constitutive equations, flow stress and globularization evolution of Ti-17 and TA15 alloys at different temperatures and strain rates were predicted. Good agreements between the experimental and computed results were obtained.
Key words: Hot forming / Unified viscoplastic constitutive equations / Lamellar microstructure / Softening mechanism / Two-phase titanium alloys / Globularization
© L. Yang et al., Published by EDP Sciences, 2016
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