Constitutive modeling and microstructure change of Ti-6Al-4V during the hot tensile deformation

Uniaxial tensile tests were performed on a Ti-6Al-4V alloy sheet over the temperature range of 923-1023 K with the strain rates of 5 x 10(-4)-5 x 10(-2) s(-1) up to a 25% length elongation of the specimen. The true stress-strain curves reveal that the flow stress decreases with the increase of the temperature and the decrease of the strain rate. In the same process, the accompanying softening role increases. On the basis of these experimental data, the Arrhenius-type equation was investigated to characterize the hot deformational behavior. Four material constants were determined to be the fourth-order polynomial functions of true strain. The equations show that the flow stress depends on strain, strain rate and temperature. Further, the microstructures, the grain sizes and the microhardnesses of the deformed specimens were measured. The observed results show that the microstructures and the microhardnesses have not changed largely and the grain sizes fluctuate around the initial one. Thus the flow stress model is provided for the process route compiling and the finite element simulation of the hot forming process of the thin-wall Ti-6Al-4V alloy component. (C) 2012 Elsevier B. V. All rights reserved.