Anisothermal large deformation constitutive equations and their application to modelling titanium alloys in forging

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Abstract
The paper presents constitutive equations for the large deformations of a near-α titanium alloy in forging. The equations model anisothermal behaviour and provide a description of microstructural evolution due to dynamic recrystallization. The stress-strain behaviour and the microstructural evolution are well characterized by the equations over the temperature range 400–1100°C, and strain rate range 0.005–10.0s−1. The equations are related to the underlying physics of the deformation processes, wherever possible. The material model established has been implemented into finite element software and employed to assess the suitability of the cylindrical specimen and plane-strain compression specimen tests for the generation of materials data. Whilst both test methods are found to be reasonable for the determination of stress-strain behaviour, the plane-strain compression test leads to the development of transient, strongly inhomogeneous fields of grain size. The cylindrical specimen compression test is therefore considered more appropriate for obtaining microstructural evolution data for process modelling.