The influence of aging on critical transformation stress levels and martensite start temperatures in NiTi: Part II-discussion of experimental results


Journal Article

An experimental study was performed to determine the effect of aging on martensitic transformations in NiTi. Polycrystalline and single crystal NiTi ([100], [110], and [111] orientations) were both considered. Stress-induced transformations inpolycrystalline NiTi were found to closely resemble transformations in single crystals of the [110] and [111] orientations. Solutionized and over-aged single crystals exhibited a strong orientation dependence of the critical stress required to trigger the transformation, σ cr . The Schmid law was able to accurately predict the orientation dependence of σ cr in the solutionized and over-aged single crystals. Peak-aged single crystals demonstrated a much weaker orientation dependence of σ cr and in general, the Schmid law was not obeyed. By considering the local stress fields outside of the semi-coherent precipitates, the decrease in the orientation dependence of σ cr was accounted for. The martensite start temperatures, M s , in aged single crystal and polycrystalline NiTi were much higher than in solutionized samples. In peak-aged NiTi the increase was primarily attributed to the local stress fields outside the coherent precipitates which create preferential nucleation sites for the martensite. In the over-aged NiTi the increase in M s was primarily attributed to the decrease in the average Ni concentration of the matrix surrounding the coarsened precipitates. © 1999 by ASME.

Full Text

Duke Authors

Cited Authors

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

Published Date

  • January 1, 1999

Published In

Volume / Issue

  • 121 / 1

Start / End Page

  • 28 - 37

Electronic International Standard Serial Number (EISSN)

  • 1528-8889

International Standard Serial Number (ISSN)

  • 0094-4289

Digital Object Identifier (DOI)

  • 10.1115/1.2815995

Citation Source

  • Scopus