Densification, microstructure evolution and fatigue behavior of Ti-13Nb-13Zr alloy processed by selective laser melting

Ti-13Nb-13Zr alloy was fabricated by selective laser melting (SLM), and the densification, microstructure evolution, nanohardness, tensile strength and fatigue behavior of the alloy were systematically investigated. A narrow, feasible process window (laser power 325 W, scanning speed 1000 mm/s, scanning distance 0.13 mm, and layer thickness 0.03 mm) was accordingly determined. With the increase of scanning speed, the coarse acicular-shaped α′ grains changed to refined acicular-shaped α′ grains and then defect formed in the microstructure. The optimally prepared Ti-13Nb-13Zr sample had a very high hardness of 519.448 HV and tensile strength of 1106.07 MPa, which are superior higher than that prepared by traditional thermomechanical technique (280 ± 15 HV and 732 MPa). Owing to the change of BCC to HCP structure ([111] β→ [1-21-3] α′), the accumulation of dislocations and the finer grains, the SLM-processed samples exhibited higher fatigue strength than that the alloy processed by cast and was commensurate with the cast Ti-6Al-4 V. Moreover, the influences of phase transition on fatigue behavior have been discussed carefully.