Microstructure and mechanical properties of MRI-compatible Zr-9Nb-3Sn alloy fabricated by a laser powder bed fusion process

Abstract

We investigated the microstructure, mechanical properties, and magnetic susceptibility of novel metastable β-type Zr-9Nb-3Sn alloy builds fabricated using a laser powder bed fusion (L-PBF) process. In addition to the dominating β and small amount of ω phases, a unique needle-like β´phase with a body-centered tetragonal crystal structure was formed due to the high thermal stress during the L-PBF process. The alloy builds fabricated at a higher energy density showed a〈100〉 preferential orientation parallel to the building direction, whereas random crystallographic orientation was observed in those fabricated at a lower energy density. Compared with the randomly oriented build, Young’s modulus of the oriented one was lower at 55 GPa, the tensile elongation was higher at 16%, and the tensile strength was higher at 796 MPa. The Zr-9Nb-3Sn alloy builds possess a higher yield and tensile strength compared to their as-cast counterparts. Moreover, the volume magnetic susceptibility of the alloy builds was two-thirds that of commonly used CP-Ti and Ti-6Al-4V. The combination of low magnetic susceptibility, low Young’s modulus, and moderate ductility make the Zr-9Nb-3Sn alloy a potential candidate for biomedical devices used in magnetic resonance imaging.