Exceptional Mechanical and Functional Properties of Ultrafine-Grained NbZr Biomedical Alloys

Niobium-1-3 wt.% zirconium (NbZr) alloys demonstrate exceptional mechanical properties in UFG condition. In this talk, we will summarize the unconventional mechanical and functional properties of UFG NbZr samples that were processed using ECAP at room temperature. Monotonic tensile and low-cycle fatigue responses and the corrosion fatigue behavior in simulated body fluid (SBF) will be reported. The room temperature processing resulted in UFG microstructure, high density of high angle grain boundaries, a favorable combination of high strength and ductility with superior biocompatibility and excellent corrosion resistance. The corrosion resistance of UFG NbZr was similar to that of Ti-6Al-4V. Highcycle fatigue tests showed no alteration in the crack initiation behavior due to the SBF environment, and absence of pitting and corrosion products. Internal oxidation of UFG NbZr formed nano-ZrO2 precipitates on the surface, significantly intensified the surface hardness without deterioration of the surface quality, and thus remarkably improved the fatigue performance.