Phase transformation and constitutive models of a hot compressed TC18 titanium alloy in the α+β regime

The flow behaviors of TC18 titanium alloy are studied in the α+β regime by hot compression tests at the strain rates of 0.001-0.1 s−1 and temperatures of 1033-1123 K. The deformation characteristics of this alloy are greatly influenced by deformation conditions. The stress descends with the decreased strain rate or the increased temperature. The dynamic recrystallization behavior becomes weaken, while the dynamic recovery behavior tends to be more obvious with increasing deformation temperature. The deformation storage energy can effectively promote the transformation from α phase into β phase. Meanwhile, the β phases permeate into the lamellar α phases, resulting in the fragmentation and spheroidization of lamellar α phases. Three constitutive models, including the strain-compensated Arrhenius-type, Hensel-Spittel (HS) and artificial neural network (ANN) models, are constructed to depict the flow behaviors of the studied alloy. The correlation coefficients of the measured and predicted results are 0.9866, 0.9739 and 0.9971, respectively, for the constructed strain-compensated Arrhenius-type, HS and ANN models. Also, their average absolute relative errors are 6.51%, 8.30% and 1.68%, respectively. Therefore, three models can well describe the flow behavior of the studied alloy, and the prediction accuracy of ANN model is the best among three constitutive models.