[T6] AM Beam Based Technologies

[15B-T6-24] Basal Oriented Columnar Microstructure Formation in Laser Powder Bed Fusion Prepared α Titaium Alloy

*S. Kariya¹, H. Hanada¹, A. Issariyapat¹, J. Umeda¹, K. Kondoh¹ (1.Osaka University, Japan)

Keywords:LPBF, Titanium, α titanium alloy, Texture

Laser Powder Bed Fusion (LPBF) titanium alloys are known to have a strongly oriented columnar microstructure, but this is limited to β-titanium alloys, and α-titanium alloys show an acicular microstructure resulting from martensitic transformation. In contrast, by optimizing the LPBF conditions, we were able to form a strong basally oriented columnar microstructure. In this study, we investigated the mechanism of microstructure formation through detailed microstructural analysis and experimental verification. It was clarified that these columnar grains were formed as a result of grain growth of the columnar grains in the lower layer consuming fine acicular grains resulting from martensitic transformation in the heat-affected zone formed during the building of the upper layer. The grain growth rate is higher in the c-axis compared to the a-axis of hcp, and it is concluded that a basal orientation with the c-axis aligned with the grain growth direction was selected.