• Schell, N.
• Benafan, O.
• Wood, L.
• Zhou, N.
• Oliveira, João Pedro

Abstract

High temperature shape memory alloys are currently attracting significant attention by the aerospace industrydue to the potential use of shape memory and superelastic properties at temperatures above 100 °C. Virtuallyany advanced engineering materialmust, at some point, be joined either to itself, to create complex shaped structures,or to other materials to increase its potential applications. In this work, laser welding of a precipitationstrengthened Ni-rich NiTiHf high temperature shape memory alloy is reported for the first time. Starting witha base material aged at 500 °C for 3 h and air cooled, defect-free joints with a conduction weld mode were obtained.Microstructural characterization, facilitated via microscopy and synchrotron X-ray diffraction, revealedthat the fusion zone contained a single-phasemartensitic structure at roomtemperature, compared to a mixtureof martensite and H-phase precipitates in the basematerial. Isothermal loading in both the martensite (at 30 °C)and austenite (at 200 °C) phases revealed equivalent strength and near-perfect superelasticity in the welded andun-welded reference material.

Topics

• impedance spectroscopy
• phase
• scanning electron microscopy
• x-ray diffraction
• strength
• defect
• precipitate
• precipitation
• microscopy