Thermal, Mechanical, and Electrochemical Characterization of Ti50Ni50−XMox Alloys Obtained by Plasma Arc Melting

Abstract

This study aims to manufacture and characterize titanium and nickel alloys with different molybdenum (Ti–Ni–Mo) contents, focusing on the influence of these additions on the microstructure, mechanical properties, and corrosion resistance. The relevance of this work stems from the lack of research on this specific alloy and the absence of reports in the literature with molybdenum percentages above 2 at.%. Ti50Ni50−XMox alloys were produced by the plasma arc melting method, with six different compositions (x = 0, 0.5, 1, 2, 3, and 4 at.% Mo), and a comprehensive analysis of microstructure, chemical composition, thermal, mechanical, and electrochemical properties was carried out. The results demonstrated significant alterations in the microstructure of the Ni–Ti alloy with the addition of molybdenum presenting several phases, precipitates (TiNi, Ti2Ni), and oxides (Ti4Ni2O, TiO, and TiO3). The stability of the B2 phase increased with molybdenum content, and the monoclinic martensite (B19′) phase was identified only in the Ni–Ti sample. Introducing molybdenum into the Ni–Ti alloy generated the R-phase and shifted the phase transformation peaks to lower temperatures, as differential scanning calorimetry (DSC) indicated. Microhardness and elastic modulus decreased with increasing Mo content, ranging from 494 HV to 272 HV and 74 GPa to 63 GPa, respectively. Corrosion tests revealed increased corrosion resistance with increasing Mo content, reaching a polarization resistance of 2710 kΩ·cm2 and corrosion current of 11.3 µA. Therefore, this study points to Ti–Ni–Mo alloys as potential candidates to increase the range of Ni–Ti alloy applications, mainly in biomaterials, reinforcing its relevance and need in current alloy research.