Effects of tantalum addition on microstructure and properties of titanium alloy fabricated by laser powder bed fusion

The expanding of material library of laser powder bed fusion (L-PBF) is of great significance to the development of material science. In this study, the biomedical Ti-13Nb-13Zr powder was mixed with the tantalum particles (2 wt%-8 wt%) and fabricated by L-PBF. The microstructure consists of a beta matrix with partially unmelted pure tantalum distributed along the boundaries of molten pool owing to the Marangoni convention. Because the melting process of Ta absorbs lots of energy, the size of molten pool becomes smaller with the increase of Ta content. The fine microstructure exists in the center of melt pool while coarse microstructure is on the boundaries of melt pool because of the existence of heat-affected zone. The columnar-to-equiaxed transitions (CETs) happen in the zones near the unmelted Ta, and the low lattice mismatch induced by solid Ta phase is responsible for this phenomenon. The recrystallization texture is strengthened while the fiber texture is weakened when the tantalum content is increased. Due to the formation of refined martensite alpha ' grains during L-PBF, the compressive strengths of L-PBF-processed samples are higher than those fabricated by traditional processing technologies. The present research will provide an important reference for biomedical alloy design via L-PBF process in the future.

Automated summary

In this study, biomedical Ti-13Nb-13Zr powder mixed with tantalum particles was fabricated using L-PBF, resulting in a microstructure with beta matrix and unmelted tantalum distributed along the molten pool boundaries. Increasing tantalum content reduced molten pool size and resulted in finer microstructure at the center and coarser microstructure at the boundaries of the melt pool. Columnar-to-equiaxed transitions occurred near unmelted tantalum, with low lattice mismatch induced by solid tantalum phase. Recrystallization texture was strengthened and fiber texture weakened with increasing tantalum content. The formation of refined martensite alpha ' grains during L-PBF led to higher compressive strengths compared to samples fabricated using traditional methods, setting an important reference for future biomedical alloy design via L-PBF process.