Mechanical behavior of a Ti-6Al-4 V titanium alloy with microstructural evolution modeling under hot and superplastic conditions

The present work aims at evaluating and understanding the mechanical behavior of a Ti-6Al-4 V alloy under hot and superplastic forming conditions. Tensile tests were performed at temperature range from 650 degrees C to 950 degrees C, at strain rates between 10(-2) s(-1) and 10(-4) s(-1). Three equiaxed microstructures, each characterized by a different starting grain size (4.9 mu m, 3.0 mu m and 0.5 mu m), are compared to better understand the microstructural evolutions under hot and superplastic forming conditions and their influence on the mechanical behavior. Hence, an accurate model with microstructural considerations is proposed. The model capabilities consider the grain size evolution that is influenced by the temperature and deformation. The computed flow stresses strongly depend on the strain rate and on the considered initial grain size. Temperature and strain rate conditions may lead to a strain hardening phenomenon in some cases. The comparison between the model response and experiment shows a good agreement for all the tests carried out on Ti-6Al-4 V.