Abstract
<jats:p>Simultaneous doping of TiNi alloy with copper and zirconium by substituting zirconium for titanium and copper for nickel while maintaining the quasi-binary (Ti35Zr15)(Ni35Cu15) composition enables the formation of two fundamentally different phase states – amorphous and crystalline – as a result of exposure of the material to low- and medium-energy ion beams. An amorphous layer synthesised from the same alloy on the surface of a medical implant made of a Ti–Ni–Cu–Zr alloy, not functional (stents, occluders), but structural (intervertebral discs, orthopedic braces), will allow protecting effectively the implant from the permanent effects of aggressive biological environments of any type (biological fluids, soft tissue, and bone). However, ion-beam modification of the Ti–Ni–Cu–Zr alloy surface can induce residual stresses that can change the properties of the original material. According to X-ray diffraction analysis, niobium ion treatment results in the formation of a layered structure with an amorphous-crystalline surface layer, a B2 matrix phase, and secondary (Ti,Zr)2(Ni,Cu) and TiZr phases. It was found that the B2 phase is a superposition of two phases, one of which, B2core, predominates in the deeper layers of the sample, while B2surf, conversely, is formed primarily in the surface layers. Analysis of the elastic stress state revealed that beneath the ion-modified surface layer, the B2surf phase is in a tensile state, while the B2core phase is in a compressed state, which indicates a complex interaction between the phases and the fact that the stresses in them can mutually compensate for each other. The obtained results are important for understanding the influence of ion implantation on the structure and properties of Ti35Ni35Cu15Zr15 alloys and optimising processing modes for medical applications.</jats:p>