Thermal treatment of NiTi alloys allows influencing of superelastic behavior through microstructure changes significantly. The appropriate thermal regime is able to move austenite-martensite transformation temperatures. The aim of the work was the study of microstructure of NiTi specimens with 55.85 wt.% Ni of the wire shape before and after the thermal treatment. The heat regimes were performed at these conditions: solution treatment at 600 °C for 1 hour followed by water quenching; ageing at eight different temperatures (250, 270, 290, 300, 350, 400, 450 and 500 °C) for 30 minutes. Microstructures features were studied by means of optical and scanning electron microscopies, EDX microanalysis and microhardness measurement. Higher ageing temperatures led to an increase in microhardness and microstructure changes.Keywords: NiTi, heat treatment, ageing, microstructure, SEM/EDX analyses
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