Low temperature relaxation of residual stress in Ti-6Al-4V

Isothermal tests were performed on Ti-6Al-4V to observe time-dependent changes in the lattice parameter of the α (hexagonal close-packed) and β (body-centered cubic) phases. Synchrotron-based experiments show contraction in β at temperatures below 550 °C, and expansion at higher temperatures. Contraction results from annealing of preexisting residual stresses, while expansion results from V diffusion when the α → β phase transformation becomes kinetically active.