Micro and macro deformation of single crystal NiTi

Published

Journal Article

We present experimental results on the instrumented Vickers micro-indentation and compression of solutionized Ni-rich NiTi single crystals. The tests are conducted at room temperature where the solutionized Ti-50.9 at percent Ni material is 18 degrees above A f and the solutionized Ti-51.5 at percent Ni material is more than 100 degrees above A f . Aside from elastic deformation, it is discovered that dislocation motion and a reversible stress-induced martensitic transformation influence the micro-indentation response of Ti-50.9 at percent Ni, while the micro-indentation of Ti-51.5 at percent Ni only induces irreversible dislocation motion. The effect of the surface normal orientation on material hardness was negligible in the Ti-51.5 at percent Ni and followed trends anticipated by the activation of favorable slip systems in the Ti-50.9 at percent Ni. Compression tests on the identical Ti-50.9 at percent Ni samples revealed deformation by coupled stress-induced martensite and plastic flow, depending on the crystallographic orientation. The trends in hardness with surface normal orientation were not commensurate with the orientation dependence of the uniaxial compressive transformation or "yield" strength. The ramifications of the results in terms of comparing micro-indentation and macro-compression and the interactions between plasticity and the stress-induced martensitic transformation are discussed.

Full Text

Duke Authors

Cited Authors

  • Gall, K; Dunn, ML; Liu, Y; Labossiere, P; Sehitoglu, H; Chumlyakov, YI

Published Date

  • April 1, 2002

Published In

Volume / Issue

  • 124 / 2

Start / End Page

  • 238 - 245

International Standard Serial Number (ISSN)

  • 0094-4289

Digital Object Identifier (DOI)

  • 10.1115/1.1416684

Citation Source

  • Scopus