Tension-compression asymmetry of the stress-strain response in aged single crystal and polycrystalline NiTi

Published

Journal Article

The purpose of this work is to thoroughly understand tension-compression asymmetry in precipitated NiTi using unique experimental results and micro-mechanical modeling. For the first time, tensile and compressive stress-strain behaviors were established on aged single crystals ([100], [110], and [111] orientations) and polycrystalline NiTi. The single crystal and polycrystalline Ti-50.8 at.% Ni materials were given both peak aged and over aged heat treatments. The drawn polycrystalline NiTi has a strong texture of the 〈111〉{110} type, thus it deformed in a manner consistent with the [111] single crystals. In contrast to the phenomenological theory of martensitic transformations (analogous to Schmid's law), the critical resolved shear stress required to trigger the transformation, τ crss , in the peak-aged single crystals was dependent on both the stress direction and crystallographic orientation. Using micro-mechanical modeling, the deviation from Schmid's law was attributed to the unique orientation relationship that exists between the Ti 3 Ni 4 precipitates (their coherent stress fields) and the 24 martensite correspondence variant pairs. The over-aged single crystals generally obeyed Schmid's law within experimental error, consistent with the proposed micro-mechanical model. Qualitatively, the tension-compression asymmetry and orientation dependence of the recoverable strain level, ε 0 , was consistent with the phenomenological theory for martensitic transformations. However, the peak- and over-aged single crystals generally both demonstrated smaller ε 0 magnitudes than predicted. The differences for both crystals were attributed to the inhibition of martensite detwinning coupled with several unique microstructural effects.

Full Text

Duke Authors

Cited Authors

  • Gall, K; Sehitoglu, H; Chumlyakov, YI; Kireeva, IV

Published Date

  • March 10, 1999

Published In

Volume / Issue

  • 47 / 4

Start / End Page

  • 1203 - 1217

International Standard Serial Number (ISSN)

  • 1359-6454

Digital Object Identifier (DOI)

  • 10.1016/S1359-6454(98)00432-7

Citation Source

  • Scopus