On the creep performance of the Ti‐6Al‐4V alloy processed by additive manufacturing

The creep response of a Ti‐6Al‐4V alloy produced by additive manufacturing was investigated at 500, 600, and 650 °C using constant load experiments. A collection of recent data from the literature on Ti‐6Al‐4V produced by conventional technologies and heat treated to produce different microstructures was analysed to determine the effect of the microstructure on the creep behaviour of this material. A unique constitutive equation derived from a model developed for face-centred cubic (fcc) metals was successfully used to describe the creep response, irrespective of the different microstructures. The same constitutive model was able to provide an excellent description of the minimum creep rate dependence on the applied stress for the alloy produced by additive manufacturing, notwithstanding the obvious differences in the microstructures. These observations led to the reconsideration of some consolidated opinions on the behaviour of Ti‐6Al‐4V, shedding light on the substantial similarities in the creep responses when the microstructure has different morphologies. The initial microstructural features, which have traditionally been thought to greatly influence the creep response, indeed played an important role because they determined the magnitude of the ultimate tensile strength, but this effect gradually disappeared at high temperatures and low stresses.