Biomedical core–shell micro-nanocrystalline Ti6Al4V5Cu alloy with high fatigue properties

Abstract

Fatigue strength is one of the most important indicators used to evaluate titanium alloy orthopedic implants. Sufficient fatigue strength can enhance the reliability of orthopedic implants. It is well known that grain refinement is beneficial to enhancing material strength but against fatigue resistance. This work has fabricated a triple-phase core–shell micro-nanostructure in a biomedical Ti6Al4V5Cu alloy with the ultrafine grained α phase stabilized by the nanoscale conjugated β/Ti2Cu shells, of which results in a high fatigue resistance. The results show that the average grain size of the α, β, and Ti2Cu phases are 585 nm, 421 nm and 135 nm, respectively. The soft β phases in the conjugated β/Ti2Cu shells can produce a plastic zone at the crack tip to hinder the propagation of fatigue cracks. The fatigue strength of the core–shell structured Ti6Al4V5Cu alloy is 750 MPa under the experimental condition of R = -1 andNf = 107, which is 36.3 % higher than the widely used Ti6Al4V alloy. The mechanisms for improving the fatigue properties have also been discussed. These are of great significance for the development of a new generation of high fatigue strength titanium alloys.