Young’s modulus and damping in dependence on temperature of Ti–6Al–4V components fabricated by shaped metal deposition

Abstract

Young’s modulus and damping behavior is investigated by the impulse excitation technique in vacuum up to 1100 °C for Ti–6Al–4V components, fabricated by shaped metal deposition (SMD). This is a novel additive manufacturing technique where near net-shape components are built layer by layer by tungsten inert gas welding. The Young’s modulus decreases linearly from 118 GPa at room temperature to 72 GPa at 900 °C, followed by a stronger decrease up to 1000 °C and during the first heating a plateau thereafter. The damping exhibits an exponential increase with temperature superimposed by two peaks around 700 and 900 °C during the first heating. During cooling and follow-up cycles only the damping peak around 700 °C appears. The change in Young’s modulus and the damping behavior is interpreted by different processes like α/β transformation, O alloying and grain boundary sliding. These results indicate that components fabricated by SMD contain a non-equilibrium α phase which transforms to the β phase at higher temperatures than the equilibrium α phase. Furthermore, the vacuum between 2.4 and 5.3 × 10−4 mbar proved at high temperatures to be not good enough to rule out the contamination by O, which leads to α casing, stiffening, and hardening.