Abstract
Minimizing phase transformation (PT) hysteresis is of crucial importance for reliability of shape memory alloy (SMA)-based devices, where the lattice strain/stress caused by thermal hysteresis leads to functional degradation. As a result, understanding structural factors that control PT pathway is critical for development of materials with high reversibility. In this study, two distinct PT mechanisms (from γ1' martensite to β1 austenite phase) in Cu–Al–Ni SMAs were revealed by in-situ TEM observation. A growth-dominant conventional PT mechanism shows in the fast quench sample, whereas a nucleation-dominant PT mechanism that suppresses interface propagation and induces high thermal hysteresis displays in the slow quench sample. By characterizing the atomic scale composition and microstructure we discover that slow quenching induces nanoprecipitation that changes chemistry of the matrix alloy, which in turn causes the higher PT hysteresis and temperature, while fast quenching avoids the formation of these nanoprecipitates. Our finding provides valuable insights into the fabrication of SMAs with better reliability.
| Original language | English |
|---|---|
| Article number | 151743 |
| Journal | Journal of Alloys and Compounds |
| Volume | 808 |
| DOIs | |
| State | Published - Nov 5 2019 |
Funding
This work was supported in part by Laboratory Directed Research and Development funds through Ames Laboratory and by the U.S. Department of Energy, Office of Science , Basic Energy Sciences, Materials Science and Engineering Division. Ames Laboratory is operated for the U.S. Department of Energy by Iowa State University under Contract No. DE-AC02-07CH11358 . All TEM related work was performed in the Sensitive Instrument facility in Ames lab. APT research was conducted at ORNL's Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility. This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).This work was supported in part by Laboratory Directed Research and Development funds through Ames Laboratory and by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division. Ames Laboratory is operated for the U.S. Department of Energy by Iowa State University under Contract No. DE-AC02-07CH11358. All TEM related work was performed in the Sensitive Instrument facility in Ames lab. APT research was conducted at ORNL's Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility.? This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).
Keywords
- Atom probe tomography
- In situ transmission electron microscopy
- Phase transition
- Shape memory alloy