Theory-guided design of Ti-based binaries for human implants

The improvement of hip transplants is severely hampered by the lack of suitable materials which are biocompatible in terms of non-toxicity and mechanical properties matched to the bone. The aim of our research has been therefore to identify metallurgical trends for non-poisonous Ti-based alloys employing quantum-mechanical calculations. Specifically, density functional theory (DFT), a plane wave basis set and PAW pseudopotentials have been used. As a first step the thermodynamic stability of Ti-Mo and Ti-Nb binaries has been determined. Second, the Young modulus of the thermodynamically stable alloys has been calculated and an alloy composition that maximally matches human bone has been selected. Guided by the theoretical calculations of phase stability and elastic properties, selected binaries were actually melted, cast, and heat treated to a homogeneous state. The samples have been experimentally characterized by x-ray methods, electron microscopy including crystallographic and chemical analysis, and mechanically tested using ultrasound measurements. The experimental data obtained in these experiments are in excellent agreement with the theoretical predictions