Publication Date

7-2018

Department

Ames Laboratory; Materials Science and Engineering

Campus Units

Materials Science and Engineering, Ames Laboratory

Report Number

IS-J 9646

DOI

10.1016/j.actamat.2018.04.042

Journal Title

Acta Materialia

Volume Number

153

First Page

15

Last Page

22

Abstract

Alnico is a prime example of a finely tuned nanostructure whose magnetic properties are intimately connected to magnetic annealing (MA) during spinodal transformation and subsequent lower temperature annealing (draw) cycles. Using a combination of transmission electron microscopy and atom probe tomography, we show how these critical processing steps affect the local composition and nanostructure evolution with impact on magnetic properties. The nearly 2-fold increase of intrinsic coercivity (Hci) during the draw cycle is not adequately explained by chemical refinement of the spinodal phases. Instead, increased Fe-Co phase (α1) isolation, development of Cu-rich spheres/rods/blades and additional α1 rod precipitation that occurs during the MA and draw, likely play a key role in Hci enhancement. Chemical ordering of the Al-Ni-phase (α2) and formation of Ni-rich (α3) may also contribute. Unraveling of the subtle effect of these nano-scaled features is crucial to understanding on how to improve shape anisotropy in alnico magnets.

Language

en

Department of Energy Subject Categories

36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY

Publisher

Iowa State University Digital Repository, Ames IA (United States)

Available for download on Monday, July 01, 2019

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