Microstructure, mechanical and biological properties of zirconium alloyed with niobium after severe plastic deformation

A comparative investigation of microstructure, mechanical and biological properties for zirconium alloyed with niobium in coarse-grained and ultra-fine grained states is presented. The temperature and deformation regimes of multi-stage abc-pressing resulted in ultra-fine grained states with an average size of the structural elements in the range of 0.28-0.55 μm, depending on the accumulated strain during pressing. The increase of the accumulated strain at each stage of pressing increased the uniformity of the structure. The microhardness increased by 50% with increased accumulated strain during the severe plastic deformation. Between the microhardness and the average size of the structural elements, a linear dependence was found, indicating a Hall-Petch relationship. The alloy had a good biocompatibility as shown by an MTT test with osteoblasts (MG-63 cell line). The good mechanical properties (microhardness) of zirconium alloyed with niobium in the ultra-fine grained state make it suitable for medical applications, e. g. as implant material.