Effect of post-heat treatment with super β transus temperature on the damping behaviour of LPBF-processed Ti6Al4V thin rotor blade

Abstract

This article investigates the damping behaviour of laser powder bed fusion-processed Ti6Al4V thin plate samples and thin rotor blades. The effect of microstructural changes owing to the post heat treatments (PHTs – 850 °C, 950 °C and 1050 °C) on damping behaviour was assessed. The microstructural characterisation was performed using optical microscopy, X-ray diffraction and scanning electron microscope techniques. The impact hammer test was performed on thin plate samples and rotor blades to characterise damping behaviour. The microstructure of the thin plate samples subjected to PHT conditions varied in grain structure and morphology compared to the as-printed ones. Further, PHT at a higher temperature (i.e. 1050 °C) induces a higher amount of β phase than the other PHT temperatures. The PHT performed at 1050 °C exhibited α- Widmanstätten microstructure consisting of elongated β and a small amount of α. Moreover, the frequency response function plots revealed broader peaks for thin plate samples and the rotor blade than others. The PHT was favourable in enhancing the α lath thickness and β volume fraction, increasing the damping ratio. The results showed that PHT performed at 1050 °C improves the overall damping of ∼348% and ∼140% of rotor blade and thin plate samples, respectively. The amplitude decay for the rotor blade subjected to PHT at 1050 °C was ∼66% shorter than the as-printed one due to high β phase content relieving the energy resulting in a high damping ratio.