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

Thermal expansion and lattice parameters are investigated up to 1100 degrees 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 x 10(-5) K-1 during heating up to 1100 degrees C, not reflecting the alpha to beta phase transformation. During cooling a stalling of the contraction is observed starting at the beta transus temperature. These high temperature experiments denude the alpha phase of V and enrich the beta 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 alpha than for the beta phase. With increasing temperature the unit cell volume of the beta phase increases stronger than the one of the alpha phase resulting in a similar unit cell volume at the beta 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. (C) 2010 Elsevier B.V. All rights reserved.