Metallurgy and magnetism of soft magnetic iron-aluminum alloys
Abstract
Soft magnetic materials are important engineering materials especially in energy generation, electromechanical devices and automotive applications. Soft magnetic materials generally have poor mechanical properties particularly at elevated temperatures. However, in many applications, soft magnetic materials with higher strength at elevated temperatures are needed. Iron-aluminum alloys have potential as soft magnetic materials for applications requiring high strength and/or elevated temperature stability. In this investigation, iron-aluminum alloys with 0-18wt%Al were prepared by high temperature sintering of elemental powders. The AC and DC soft magnetic properties were studied at room temperature and ambient atmosphere. The influence of aluminum concentration and microstructure on the soft magnetic properties of the alloys were investigated. The effect of magnetic annealing on the soft magnetic properties was also examined. The P/M Fe-(1-18wt%)Al alloys were single phase, disordered α-FeAl. Magnetic induction, residual induction, coercivity, maximum permeability and hysteresis losses were correlated with alloy composition, porosity, pore morphology and grain size. Magnetic induction and density decreased linearly with increasing aluminum. Magnetic induction, density and pore morphology were related by a power law equation. Coercivity and maximum permeability also showed strong dependence on aluminum concentration. Fe-1wt%Al, with large grain diameter (D∼155μm) and low porosity (<2%) had room temperature AC and DC magnetic properties superior to pure iron processed under the same conditions. The critical temperature for grain growth in Fe-1wt%Al was 2400°F (1316°C). Fe-5wt%Al had intermediate grain size (D∼100μm), the highest hardness and the lowest AC power loss. While Fe10wt%Al had smaller grain size (D∼85μm) and higher porosity, the DC magnetic properties showed the largest response after magnetic annealing. Experiments demonstrated that Fe-18wt%Al was a weak ferromagnetic material but can be strengthened by precipitating second phase Fe3 Al particles in the alloy by heat treatment. Iron-aluminum alloys are versatile soft magnetic alloys for applications requiring strong magnetic properties with low energy losses and/or high strength at room and elevated temperatures.
Recommended Citation
Elizabeth Carie Buc,
"Metallurgy and magnetism of soft magnetic iron-aluminum alloys"
(January 1, 2004).
ETD Collection for Wayne State University.
Paper AAI3130330.
http://digitalcommons.wayne.edu/dissertations/AAI3130330
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