The influence of nitinol structure on oxidation features when heated and on corrosion resistance in chloride-containing solutions

Abstract

Using the methods of differential thermal analysis and voltammetry the authors have studied the influence of grain-subgrain structure of alloys on the basis of nitinol Ti49,5Ni50,5 and Ti50,0Ni47,3Fe2,7 on the laws of their oxidation when heated in air and on corrosion resistance in chloride-containing solutions (0,9 % NaCl, artificial sea water). The alloy with submicrocrystalline structure was prepared by equal-channel angle pressing in 1-3 passages, minimum average size of grain/subgrain achieved 0,25μ. It was shown that decreasing element size of grain/subgrain structure results in reduction of alloy thermal oxidation stability which appears in fall of oxidation begining tempearture, temperatures of achieving process peak rate and full oxidation. When applying electropolishing and ion-beam processing of surface the corrosion resistance is determined to a great extent by surface state but not by alloy bulk structure. Using the mechanical polishing the iron-doped alloy with submicrocrystalline structure is more corrosion resistive than undoped TiNi with coarse-grain structure