Degree Type

Dissertation

Date of Award

2018

Degree Name

Doctor of Philosophy

Department

Materials Science and Engineering

Major

Materials Science and Engineering

First Advisor

Iver E. Anderson

Abstract

Economic uncertainty in the rare earth (RE) permanent magnet (PM) marketplace as well as a quickly evolving electric drive motor market which has decided to leverage permanent magnet synchronous AC drive (PMAC) motors as the motor of choice, has driven renewed research in RE-free permanent magnets such as “alnico.” Alnico, essentially an Al-Ni-Co-Fe magnet alloy, was displaced for high energy density applications by RE-containing magnets in the 1970’s due to their high-energy performance and high coercivities.

The current PMAC development trajectory requires the development of a sustainable magnet material choice, which not only has impressive mechanical properties, such as those typical of sintered alnico and superior to the RE-containing magnet technologies, but also complementary improved magnetic properties sufficient for new PMAC designs. Further, the technique utilized for consolidation and final processing must support large-scale mass production, which would be required for use in an electric drive vehicle marketplace.

Estimates are currently that a 40% year over year growth will continue to exist in the electric vehicle marketplace, requiring the production of tens of millions of magnets growing simultaneously with the EV market, something the rare earth magnet producers will continue to find challenging as net-shape capabilities are not a strong suit of their current production process.

Using high-pressure gas atomized (HPGA) isotropic “alnico 8H” based powder; fully dense magnets were able to be produced, with magnetic properties that were comparable to their cast counterparts, and in fact superior in many ways. The net shape magnets were subjected to mechanical and magnetic techniques to induce some solid-state texturing. Results for density, microstructure, and magnetic properties were measured, and show a direct correlation between the application of the texture processes and corresponding increases in remanent magnetization and energy products.

Lastly, investigations of the temperature phase space for the alloy compositions used was explored to look for opportunities to further enhance processing control through high-temperature x-ray diffractometry, differential scanning calorimetry, and thermal gravimetric analysis.

DOI

https://doi.org/10.31274/etd-180810-6020

Copyright Owner

Aaron Gregory Kassen

Language

en

File Format

application/pdf

File Size

177 pages

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