In this study, preheated Ti-6V-4V powder from electron beam melting (EBM) additive manufacturing (AM) were experimentally characterized. In the EBM AM process, preheating serves to aggregate the precursor powder, lightly sintered to prevent from the spreading effect. Specimens with sintered Ti-6AL-4V powder enclosed were fabricated and prepared using metallographic means for microstructural and morphology examinations by optical microscopy and scanning electron microscopy. In addition, micro-CT scan was conducted on the specimens and analyzed to study the powder porosity and the powder size distributions. Moreover, the thermal conductivity of preheated powder from EBM AM was measured and analyzed at different temperatures. The results are summarized as follows. Preheating results in metallurgical bonds or even partial melting of the powder. Neck formations are clearly evident in both the Z-plane and Xplane samples. The diameter of the necks is on the order of 1 to 10 μm. In addition, micro-CT analysis shows a similar porosity level between the Z-plane and the X-plane sections. The calculated porosity of the preheated powder is about 50%. Moreover, the major diameter range of the powder is from 30 to 50 μm. The Ti-6Al-4V powder has significantly lower thermal conductivity than that of a solid. The thermal conductivity of Ti-6Al-4V powder is also highly temperature dependent, about 0.63 W/m·K at the room temperature and less than 2.44 W/m·K at 750°C.
展开▼
