Mechanical properties of TiNi thin wires after synthesis of the Ti-Ni-Ta-based surface alloy using low-energy high-current electron beam

Abstract

The paper investigates mechanical properties of TiNi thin wires of a diameter ~950 µm after the synthesis of the surface alloy based on the Ti-Ni-Ta system with the amorphous structure and a thickness of ≤ 2 µm. The surface alloy is synthesized during 30 cycles of deposition and melting of the alloying film Ti₆₀Ta₄₀ (at.%) ~50 nm thick consisting of a film/substrate liquid-phase mixture using a wide-aperture (up to ~10 cm²), low-energy (≤ 30 keV), high-current (up to ~25 kA) pulsed electron beam with ~2.5 J/cm² energy density and ~2–3 μs pulse duration in one vacuum cycle. The deformation behavior of thin wires is studied in torsion tests at ~6% cyclic loading (20 cycles) and loading to failure. During cyclic loading, the synthesized surface alloy shows no critical effect on the inelastic behavior of TiNi thin wires. According to tests to failure, the shear strength and failure strain decrease by ~350 MPa and ~11%, respectively, as compared to those of the initial TiNi alloy. After torsion tests, the amorphous surface alloy does not delaminate from the surface. With regard to the low adhesive resistance of the Ti-Ta coating leading to its delamination from TiNi alloy surface, the synthesized surface alloy being an alternative coating, demonstrates positive results of mechanical torsion tests.