Hot Rolling Effects on the Microstructure and Chemical Properties of NiTiTa Alloys
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In the present paper, a Ni-37Ti-15Ta (wt.%) shape memory alloy was analyzed in as-cast and hot-rolled conditions, by differential scanning calorimetry, scanning electron microscopy coupled with energy-dispersive spectroscopy, x-ray diffraction and electrochemical tests into a simulated body fluid (SBF). Both processing states experienced reversible martensitic transformations, with lower temperatures of reverse transformation at hot-rolled specimen, where the amount of secondary phases suffered contrary variation tendencies: β-Ta solid solution increased and (Ti,Ta)2Ni intermetallic compound decreased. Hot rolling contributed to the increase in internal stresses which caused a slight decrease of 2θ angle and to the stress-induced formation of B19’ martensite from B2 parent phase. The electrochemical corrosion test, performed in an experimental SBF, emphasized the superior corrosion resistance of as-cast specimen, since it had a lower amount of internal stresses. The corrosion compounds, mostly oxides, were completely removed by ultrasonic cleaning.
Keywordscorrosion resistance differential scanning calorimetry hot rolling microstructural characterization NiTiTa SMAs
This work was supported by a research Grant of the TUIASI, Project Number 0273/2018.
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