The present paper reports on the microstructure-mechanical property relationships in an ultrafine-grained (UFG) niobium-1 wt. percent zirconium (NbZr) alloy, a potential biomedical material, severe plastically deformed at room temperature utilizing equal channel angular extrusion (ECAE). Monotonic tensile and low-cycle fatigue (LCF) experiments were carried out on the NbZr samples processed along ECAE routes 8B_C and 16E, along with extensive micro structure analysis. The important finding is that the NbZr alloy processed along ECAE routes that lead to a higher volume fraction of high-angle grain boundaries (HAGBs) exhibits a stable cyclic deformation response in the LCF regime. This stands in good agreement with prior studies on other materials, such as UFG interstitial-free steel, in which the stable fatigue behavior was associated with the dominance of HAGBs. The current results provide a venue for utilizing the UFG NbZr alloy in biomedical applications that require a combination of long-term durability, high strength and very good bio-compatibility, where the latter is not altered by ECAE processing. Furthermore, for the first time, we present guidelines for optimizing processing parameters that define the microstructure-cyclic stability relationship in UFG alloys.
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