Temperature dependent deformation of the B2 austenite phase of a NiTi shape memory alloy

    Authors

    O. Benafan; R. D. Noebe; S. A. Padula; A. Garg; B. Clausen; S. Vogel;R. Vaidyanathan

    Comments

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    Abbreviated Journal Title

    Int. J. Plast.

    Keywords

    Shape memory alloy; Austenite deformation; Neutron diffraction; Stress; induced martensite; Deformation map; INDUCED MARTENSITIC-TRANSFORMATION; SITU NEUTRON-DIFFRACTION; SINGLE-CRYSTAL NITI; TI-NI; SUPERELASTIC NITI; CYCLIC DEFORMATION; CONSTITUTIVE MODEL; TEXTURE ANALYSIS; PSEUDOELASTICITY CHARACTERISTICS; MECHANICAL-PROPERTIES; Engineering, Mechanical; Materials Science, Multidisciplinary; Mechanics

    Abstract

    Temperature dependent deformation of the B2 austenite phase of a polycrystalline Ni49.9Ti50.1 (at.%) shape memory alloy was studied through combined macroscopic and microstructural characterization efforts. The objective was to determine mechanisms responsible for the macroscopic inelastic strains during isothermal loading of NiTi to 18% strain at temperatures above which the austenite phase exists in the nominally unloaded or stress-free condition (i.e., above the austenite finish temperature, A(f)). This study included in situ time-of-flight (TOF) neutron diffraction experiments used to follow the evolution of the lattice strains, texture, and phase fractions during deformation, ex situ macroscopic tensile experiments, and hot stage transmission electron microscopy (TEM). It was found that stress-induced martensite (SIM) formed at temperatures up to 310 degrees C, which is well above the stress-free A(f) of 105 degrees C. However, the stress induced martensite formed concurrently with general < 001 > slip processes and twinning by [114}(B2) compound deformation twins, and did not occur as a separate distinguishable mechanism. Above the temperature that martensite cannot form with stress or the martensite desist temperature, M-d, deformation was governed by the same slip and deformation twinning mechanisms, in addition to diffusion-assisted deformation processes. The overall results were combined to generate a deformation map that contained limits over which each of the identified deformation mechanisms was dominant in this Ni49.9Ti50.1 alloy. Published by Elsevier Ltd.

    Journal Title

    International Journal of Plasticity

    Volume

    51

    Publication Date

    1-1-2013

    Document Type

    Article

    Language

    English

    First Page

    103

    Last Page

    121

    WOS Identifier

    WOS:000326430300006

    ISSN

    0749-6419

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