ESOMAT 2009, 06025 (2009)
DOI: 10.1051/esomat/200906025

Textural Evolution by Multiple Steps of Marforming in Ti-Rich Ni-Ti Shape Memory Alloy

A. S. Paula^{1, 2}, K. K. Mahesh^{1, 2, 3} and F. M. Braz Fernandes<sup>1, 2, 3

1</sup>  CSN – GGDP/GPD, Rod. BR 393, km 5001 – Lúcio Meira, s/n – Vila Santa Cecília – Volta Redonda – RJ – Brazil – CEP 27260-390
²  UNIFoa – Centro Universitário de Volta Redonda, Campus Três Poços – Av. Paulo Erlei Alves Abrantes, 1325, Três Poços – Volta Redonda – RJ – Brazil – CEP 27240-560
³  CENIMAT – I3N, Campus da FCT/UNL, 2829-516 Monte de Caparica, Portugal

fbf@fct.unl.pt

Published online: 1 September 2009

Abstract
The Nickel-Titanium (Ni-Ti) alloys are the most attractive amongst shape memory alloys (SMA) due to their good functionality properties coupled with high strength and good ductility. The transformation temperatures in Ti-rich NiTi SMA can be altered with suitable thermal and/or mechanical treatments to obtain martensitic transformation in one or more steps above 0°C. The goal of the present work is to investigate the textural evolution in Ti-Rich Ni-Ti SMA (Ni-51at%Ti) that will contribute to different phase transformation sequences (one, two and multiple steps) after being subjected to (i) two distinct thermal treatments (500 °C for 30 minutes in air and 800°C for 300 minutes in vacuum), (ii) followed by multiple steps of marforming (30% thickness reduction by cold rolling), intercalated with thermal treatment at 500°C for 30 minutes in air and (iii) four distinct final thermal treatments (400, 450, 500 or 600°C for 30 minutes in air). The textural results were obtained by X-Ray Diffraction (XRD) at room temperature (B19’ phase) and at 150ºC (B2 phase). Differential Scanning Calorimetry (DSC), Electrical Resistivity (ER) and X-Ray Diffraction (XRD) were used to identify the transformation temperatures and the phases that are present after all steps of thermomechanical treatments.

© Owned by the authors, published by EDP Sciences 2009