Thermophysical properties of Ti-6Al-4V fabricated by powder bed fusion methods

Three types of Ti-6Al-4V alloys were prepared by powder bed fusion methods using a laser powder bed fusion (LPBF) and two different electron-beam powder bed fusion (E-PBF) systems. The specific heat capacity, linear thermal expansion, and thermal diffusivity were measured from room temperature to similar to 1000 degrees C. The thermal conductivity values were calculated using the above values. The thermal diffusivity values of all samples along the build direction are similar and a few percent higher than those perpendicular to the build direction. The effect of measurement direction on the linear thermal expansion is evident and related to the processing conditions. A correction for the effect of low porosity (<1%) on thermal diffusivity and thermal conductivity shows that regardless of production method, the porosity corrected values are close for all the PBF samples. Attempts were made to correlate the subtle differences between the samples to the oxygen content, microstructure processing route, and preferred orientation. In the E-PBF samples with a lower cooling rate during production, thermal expansion and thermal diffusivity were nearly isotropic. The subtle changes between the E-PBF samples in both directions directly correlate to a preferred orientation parameter, the peak intensity ratio I-(002)alpha/I-((101))alpha. These results were compared to both cast and additive manufacturing literature, and differences were discussed.