Materials Science and Engineering Location: Wilsdorf Hall 200
Add to Calendar 2021-10-28T09:00:00 2021-10-28T09:00:00 America/New_York Doctoral Dissertation Proposal - Adrian Savovici Exploration of the Phase Transformations and Magnetic Properties in the Fe-Rich Fe-Pt Eutectoid Region Committee Members: Dr. Bi-cheng Zhou (Chair) - MSE Dr. William Soffa - MSE Dr. Sean Agnew - MSE Dr. Jerrold Floro (Advisor) - MSE Abstract: Wilsdorf Hall 200

Exploration of the Phase Transformations and Magnetic Properties in the Fe-Rich Fe-Pt Eutectoid Region

Committee Members:

  • Dr. Bi-cheng Zhou (Chair) - MSE
  • Dr. William Soffa - MSE
  • Dr. Sean Agnew - MSE
  • Dr. Jerrold Floro (Advisor) - MSE

Abstract:

Nanostructured exchange-coupled (EC) ferromagnets may be capable of replacing medium-strength rare-earth transition metal intermetallic magnets. Nanocomposite EC magnets also offer unique advantages, with tunability of macroscopic magnetic properties, acceptable operating temperatures, and sufficient resistance to corrosion. Due to the fine length-scales required for exchange-coupling to occur, processing difficulties are a nontrivial obstacle towards largescale production. Self-assembly through thermal treatments in intrinsic two-phase systems allows length scale control, with the added benefit of limited processing steps. The Fe-Pt system possesses narrow and poorly-explored composition regions where equilibrium of magnetically hard and soft phases and thus exchange coupling, is possible. The aim of this study is to understand phase equilibria, chemical ordering, and microstructural growth of the constituent phases in the Fe-Pt system near the Fe-rich eutectoid region under various processing techniques, and probe the relationship between microstructure and macroscopic magnetic properties.

A more complete picture of the phase transformations in this composition region, including a targeted search for novel low-temperature stable phases and higher order phase transformations should allow for more accurate processing protocols and may provide an ability to tailor new microstructures with enhanced magnetization reversal mechanisms. As such, a minimum of two compositions will be studied. A “single-phase” composition sample of Fe – 38.5 at% Pt will probe L10àL1’ transformations. A second, on-eutectoid composition sample ~Fe – 34.5 at% Pt will be used to probe the more complicated nominal two-phase (L10+L12) coexistence region. Structural analysis with x-ray diffraction and transmission electron microscopy, with a particular focus on in situ experiments, will be supplemented with magnetic characterization using vibrating sample magnetometry. Support of the National Science Foundation through grant DMR-1709914 is gratefully acknowledged.