Formation technology and structure of titanium nickelide-based alloys in double-arc melting

Abstract

Alloys based on titanium nickelides have high mechanical properties, as well as a set of special properties: shape memory effect, superelasticity, high level of damping and corrosion resistance, biocompatibility. To obtain titanium nickelides, various technologies are used: smelting in arc and induction vacuum furnaces, electrolysis of molten media, sintering, selfpropagating high-temperature synthesis, which are distinguished by high energy consumption of processes and significant cost. To reduce the cost of obtaining alloys based on titanium nickelide, a technology of double-arc melting in argon using electrode wires made of titanium and nickel was proposed, which makes it possible to obtain not only blanks and parts of the required shape from these alloys, but also deposited layers on the surface of finished products. The conducted studies of processes of titanium nickelides formation by double-arc melting showed that the chemical composition of samples is determined by modes of electric arc melting of electrode wires and, first of all, by the ratio of the feed rates of nickel and titanium wires. The nickel content in obtained samples varied within 34.1–60.1%. The structure of the samples was determined by the ratio of feed rates of electrode wires and was represented by phases: α(Ti); NiTi2; NiTi. The structure based on NiTi2 and Ti is formed when the ratio of the nickel wire feed rate to thetitanium wire feed rate is equal to 0.38. With the feed rate ratio in the range of 0.44–0.86, the structure of samples is represented by phases NiTi2 + NiTi. A single-phase structure based on titanium nickelide (NiTi) during double-arc melting in an argon atmosphere is formed at the feed rate ratio of the order of 1–1.14 of nickel and titanium wires with the same diameter.