Production of ultrafine-grain bioinert alloys

The microstructure and mechanical properties of bioinert titanium, zirconium, and niobium alloys in the ultrafine-grain state are investigated. The ultrafine-grain structure is obtained by severe plastic deformation, including multicyclic abc pressing at specified temperatures, multipass rolling in shaped rollers at room temperature, and low-temperature non-recrystallizing annealing. Annealing increases the plasticity of the ultrafine-grain alloys, without changing the grain size. As a result of two-stage treatment—severe plastic deformation and annealing—ultrafine-grain structure with grains and subgrains of mean size 0.16–0.25 μm is formed. That considerably improves the mechanical properties (ultimate strength, yield point, and microhardness) of the alloys. At the same time, the formation of ultrafine-grain structure in the alloys does not change the elastic modulus, even with considerable increase in the ultimate strength and plasticity.