Thermal expansion and lattice parameters of shaped metal deposited Ti–6Al–4V

Thermal expansion and lattice parameters are investigated up to 1100 °C for Ti–6Al–4V components, fabricated by shaped metal deposition. This is a novel additive layer manufacturing technique where near net-shape components are built by tungsten inert gas welding.The as-fabricated SMD Ti–6Al–4V components exhibit a constant coefficient of thermal expansion of 1.17 × 10−5 K−1 during heating up to 1100 °C, not reflecting the α to β phase transformation. During cooling a stalling of the contraction is observed starting at the β transus temperature. These high temperature experiments denude the α phase of V and enrich the β phase.The development of the lattice parameters in dependence on temperature are observed with high temperature X-ray diffraction. The unit cell volumes derived from these parameters are at room temperature larger for the α than for the β phase. With increasing temperature the unit cell volume of the β phase increases stronger than the one of the α phase resulting in a similar unit cell volume at the β transus temperature.These observations are interpreted as an indication for as-fabricated the SMD components being in a non-equilibrium state and reaching equilibrium during the slow heating and cooling during of the two different high temperature experiments.

Research highlights▶ Measurement of thermal expansion and of the lattice parameters of Ti–6Al–4V fabricated by shaped metal deposition up to 1100 °C. ▶ The observation of alpha to beta transformation not reflected in the expansion but in the contraction curve is explained by non-equilibrium alpha phase of the SMD material. ▶ Denuding of the α phase and enrichment of the β phase of Vanadium due to high temperature experiments. ▶ The unit cell volumes derived from lattice parameters measured by X-ray diffraction are at room temperature larger for the α than for the β phase. With increasing temperature the unit cell volume of the β phase increases stronger than the one of the α phase resulting in a similar unit cell volume at the β transus temperature.