Title: Effects of tensile loading during annealing of alnico melt spun ribbons

Abstract

Conventional magnetic annealing (MA) of the permanent magnet alloy alnico involves application of an external magnetic field at temperatures within the spinodal decomposition range. This field biases the growth of the Fe-Co rich, ferromagnetic α ₁ -phase in an energetically favorable 〈001〉 direction in alignment with the applied field within an Al-Ni rich, paramagnetic α ₂ -phase. Utilizing a magnetic field to bias the α ₁ -phase may limit alnico from reaching theoretical coercivity due to (1) the field having maximum biasing ability at temperatures near the Curie temperature where large α ₁ -phase nanorods form and (2) connectivity of the α ₁ -phase occurs unavoidably during MA. Both decrease the effective shape anisotropy of the α ₁ -phase, thereby reducing coercivity. Herein, we explore tensile-loading as a biasing mechanism to control and optimize the final alnico nanostructure beyond that achieved by MA. Two samples of melt-spun alnico were heat-treated at 860 °C for 5 minutes: one sample was subjected to 10 MPa tensile stress for comparison with a stress-free control sample. Structural and magnetic characterization revealed that the stress-annealed ribbon sample possessed expected phase assemblages, but was distinguished by a ∼2× larger grain diameter and an elongated anisotropic α ₁more » -phase within grains that were oriented to a shear stress along 〈001〉 directions at an angle of ∼45° relative to the loading direction. Both types of annealing produced a similar increase in the coercivity and remanence, but a decrease in saturation magnetization.« less

Authors:

Rinko, E. A.  ^[1];

• Search DOE PAGES for author "Rinko, E. A."
• Search DOE PAGES for ORCID "0000-0003-2910-9010"

Zhang, X.  ^[2];

• Search DOE PAGES for author "Zhang, X."
• Search DOE PAGES for ORCID "0000-0002-8256-9721"

Tang, W. ^[3]; Lewis, L. H. ^[4]; Kramer, M. J.  ^[1];

• Search DOE PAGES for author "Kramer, M. J."
• Search DOE PAGES for ORCID "0000-0002-9097-6730"

Anderson, I. E. ^[1]

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+ Show Author Affiliations

1. Materials Science and Engineering Department, Iowa State University, Ames, Iowa 50011, USA, Ames Laboratory, Division of Materials Sciences and Engineering, U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA
2. Mechanical and Industrial Engineering Department, Northeastern University, Boston, Massachusetts 02115, USA
3. Ames Laboratory, Division of Materials Sciences and Engineering, U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA
4. Mechanical and Industrial Engineering Department, Northeastern University, Boston, Massachusetts 02115, USA, Chemical Engineering Department, Northeastern University, Boston, Massachusetts 02115, USA

Publication Date:

Tue Mar 01 00:00:00 EST 2022

Sponsoring Org.:

USDOE

OSTI Identifier:

1855840

Resource Type:

Publisher's Accepted Manuscript

Journal Name:

AIP Advances

Additional Journal Information:

Journal Name: AIP Advances Journal Volume: 12 Journal Issue: 3; Journal ID: ISSN 2158-3226

Publisher:

American Institute of Physics

Country of Publication:

United States

Language:

English