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Desrilia Nursyifaulkhair,Nokeun Park,Eung Ryul Baek,Jong-bong Lee 대한용접·접합학회 2019 대한용접·접합학회지 Vol.37 No.6
The effect of different process parameters on the formation of lack of fusion (LOF) in Ti-6Al-4V alloy fabricated using DED was studied. The specific energy was calculated to evaluate the minimal amount of required energy to avoid LOF. The results showed that a specific energy smaller than 2700 J.g<SUP>-1</SUP> led to the formation of LOF; however, a higher specific energy was able to successfully prevent the defect. A smaller amount of specific energy resulted in inadequate heat, which was too low to completely melt the metal powder, and resulted in insufficient penetration depth. Subsequently, LOF was observed between the interface of the deposited layers. Furthermore, a higher powder feed rate had a more significant effect on the formation of LOF than higher laser power.
Desrilia Nursyifaulkhair,Nokeun Park,Eung Ryul Baek 대한용접·접합학회 2021 대한용접·접합학회지 Vol.39 No.5
This study investigated the effect of microstructural decomposition on the mechanical properties of additively manufactured Ti-6Al-4V by directed energy deposition. The formation of α’ martensite and α massive phase (αm) was observed in the deposited layers. The α’ and αm in the lastly deposited layer appeared as a needle-shaped and a sub-lamellar structure, respectively. However, the morphology of α’ and αm was decomposed in the lower layers due to the intrinsic heat treatment. Moreover, The heat conduction rate calculation showed that the lower powder feed rate generates more heat conduction. Therefore, the microstructure was further decomposed for the specimen with a lower powder feed rate. These phenomena consequently affected the mechanical properties and fracture behavior of the Ti-6Al-4V alloy.