Research Article

Unified constitutive modelling for two-phase lamellar titanium alloys at hot forming conditions

¹ School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China
² Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, UK

^* e-mail: nan.li@imperial.ac.uk

Received: 11 June 2016
Accepted: 4 September 2016

Abstract

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.