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

Young's modulus and damping behavior is investigated by the impulse excitation technique in vacuum up to 1100 A degrees 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 A degrees C, followed by a stronger decrease up to 1000 A degrees 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 A degrees C during the first heating. During cooling and follow-up cycles only the damping peak around 700 A degrees C appears. The change in Young's modulus and the damping behavior is interpreted by different processes like α/ß transformation, O alloying and grain boundary sliding. These results indicate that components fabricated by SMD contain a non-equilibrium alpha phase which transforms to the ß phase at higher temperatures than the equilibrium α phase. Furthermore, the vacuum between 2.4 and 5.3 x 10(-4) mbar proved at high temperatures to be not good enough to rule out the contamination by O, which leads to alpha casing, stiffening, and hardening.status: publishe