Mechanical properties of Ti–Ni–Ta и Ti–Ni–Ta–Si surface alloys synthesized on titanium nickelide substrates

The physical-mechanical properties of Ti–Ni–Ta and Ti–Ni–Ta–Si surface alloys (about 1 $\mu$m thick) synthesized on TiNi substrates by the additive thin-film electron-beam method and the influence of these surface alloys on the functional properties of the composite systems [Ti-Ni-Ta surface alloy/TiNi substrate] and [Ti-Ni-Ta-Si surface alloy/TiNi substrate] have been investigated. It has been found that amorphous Ti–Ni–Ta–Si surface alloy is characterized by higher strength and Young's modulus gradients than is Ti–Ni–Ta alloy, as well as by a higher ductility, which is 10% higher than that of the TiNi substrate and roughly twice as high as that of the Ti–Ni–Ta surface alloy. From the estimates of the shape memory and superelasticity effects in Ti–Ni–Ta surface alloy/TiNi substrate and Ti–Ni–Ta–Si surface alloy/TiNi substrate composite systems, it follows that synthesized amorphous surface alloy offers a nearly twofold rise in martensitic transformation stress. Moreover, the hysteresis loop in the strain–stress diagram considerably narrows compared with that of the initial TiNi substrate.