Sub-surface measurements of the austenite microstructure in response to martensitic phase transformation

Ashley Bucsek*, Hanuš Seiner, Hugh Simons, Can Yildirim, Phil Cook, Yuriy Chumlyakov, Carsten Detlefs, Aaron P. Stebner

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

In this work, we measure the microstructure response of the austenite phase during martensitic phase transformation tens of micrometers beneath the surface of a bulk single crystal nickel-titanium shape memory alloy. Using an emerging dark-field X-ray microscopy (DFXM) technique, the austenite phase fraction, relative misorientation, and elastic lattice plane strain are measured in the interior of the microstructure with a spatial resolution of 108 nm. The results show that some defects consistently induce forward transformation and delay reverse transformation, while other defects consistently impede the propagation of both forward and reverse transformation fronts. We also show that the austenite undergoes an orientation splitting wherein the austenite near the transformation front is constrained from rotating and the austenite far from the transformation front is free to rotate. Finally, we measure interfacial strain fields at the transformation front that extend tens of micrometers into the material. We use an analytical model to show how these strain fields can be explained by a lack of kinematic compatibility between the austenite and martensite phases at the austenite-martensite interface.
Original languageEnglish
JournalActa Materialia
Volume179
Pages (from-to)273-286
Number of pages14
ISSN1359-6454
DOIs
Publication statusPublished - 2019

Keywords

  • SHape memory alloy
  • Martensitic phase transformation
  • In situ
  • Synchrotron diffraction
  • X-ray diffraction

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