2 April 2008 Aluminum additions in polycrystalline iron-gallium (Galfenol) alloys
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Galfenol alloys show promise as a new magnetically activated smart material based on their unique combination of relatively high magnetostrictive performance and good mechanical robustness. Investigations of aluminum additions to single crystal iron-gallium alloys have been done previously, and the magnetostrictive response seems to follow the rule of mixtures with decreasing saturation magnetostriction with increasing aluminum content. Aluminum is assumed to substitute for Ga directly in the alloy. Directionally solidified polycrystalline Galfenol alloys with aluminum additions were produced to determine the effects on the magnetic properties. Iron-gallium-aluminum alloys were investigated for two primary reasons: (1) Fe-Al alloys are well established and are typically manufactured using conventional thermo-mechanical processing techniques such as rolling; it is anticipated that aluminum additions will aid in the development of Galfenol alloy rolled sheets (2) Gallium prices continue to rise and a cost effective alternative needs to be investigated. Several Fe-Ga-Al alloy compositions were prepared using the Free Stand Zone Melting (FSZM) directional solidification technique. Alloy composition ranges investigated include: Fe80.5GaxAl19.5-x (4.9≤x≤13), Fe81.6GayAl18.4-y (4.6≤y≤13.8), and Fe85GazAl15-z (3.75≤z≤11.25). Alloys were studied using EDS (chemistry verification), EBSD (crystallite orientation), and magnetic characterization techniques to determine the effect of aluminum addition on the polycrystalline binary Fe-Ga system. Magnetic properties such as saturation magnetostriction (λsat), piezomagnetic constant (d33), and relative magnetic permeability (μr) of directionally solidified Fe-Ga-Al polycrystalline alloys will be compared to binary Fe-Ga alloys including investigations into the crystal orientation effects on these properties. Results suggest that up to 50% aluminum can be substituted in the alloy while maintaining considerable saturation magnetostriction, > 200 ppm.
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M. D. Brooks, M. D. Brooks, E. Summers, E. Summers, R. Meloy, R. Meloy, J. Mosley, J. Mosley, "Aluminum additions in polycrystalline iron-gallium (Galfenol) alloys", Proc. SPIE 6929, Behavior and Mechanics of Multifunctional and Composite Materials 2008, 69291T (2 April 2008); doi: 10.1117/12.775789; https://doi.org/10.1117/12.775789

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