Ageing behavior of Beta-Ti21S produced by laser powder bed fusion

Beta Ti alloys represent suitable candidates for interesting biomedical applications. The lower elastic modulus compared to alpha-beta alloys (e.g. Ti6Al4V), better matches that of human bones. Furthermore, their composition can be tailored to remove elements like V, detrimental to biocompatibility. Finally, their possibility to reach a fully beta structure after rapid solidification makes them very interesting alloys for additive manufacturing. In this work, the authors considered a beta Ti21S alloy powder (15%Mo, 3.2%Al, 2.8%Nb...) processed by laser powder bed fusion. The mechanical properties in the as-built state are interesting, evidencing a low elastic modulus (53GPa), good mechanical strength (Sy=700MPa, UTS=820MPa), and good fracture elongation (e=21%). The aged alloy shows a distinct strengthening at 650°C, due to the precipitation of the alpha phase, and recovery of the original solidification microstructure. The transformation is accompanied by a reduction in ductility and an increase of the elastic modulus.