SGER: Development of a Soft Magnetic Material with Enhanced High Temperature Strength

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0100621PutatundaThe focus of the SGER grant is on a new, super-soft magnetic material with high creep strength at elevated temperatures. The alloy, iron with 10-20% aluminum, will use an innovative powder metallurgy processing route by simultaneous hot pressing and sintering. The iron-aluminum phase diagram indicates that iron with more than ten percent Al will not undergo the austenite to ferrite phase transformation. Furthermore, the addition of aluminum to iron allows for significant grain growth during sintering. Thus, it should be possible to produce a large grain size (grain diameters in excess of 1500 mm) in a super-soft magnetic material with extremely low coercivity, very high saturated magnetic induction, and very high permeability. Furthermore, the phase diagram indicates that in iron-aluminum alloys with 10-20% aluminum there is a likelihood of Fe3Al-type precipitates. These precipitates should provide barriers to magnetic domain wall movement, as well as obstacles to dislocation movement, resulting in a material with high creep strength at elevated temperatures. Iron and aluminum powders will be mixed in the requisite proportion and compacted. After compaction, the green product will be sintered at different temperatures and time periods to determine optimum processing conditions for a fully dense product. The magnetic and mechanical properties of the alloy will be characterized and compared with commercially available iron-silicon alloys and iron-phosphorus alloys. The influence of aluminum on grain growth and magnetic properties will be considered. Fine scale precipitates of Fe3Al will be produced in the matrix by a judicious mixture of cold working and annealing and subsequent quenching and aging processes. Successful processing will generate a new super soft magnetic material with excellent high temperature mechanical properties at low cost with very efficient magnetic performance and energy savings. %%%Soft magnetic materials are important engineering materials needed in power generation devices. These materials must have high magnetic permeability, low coercivity and high saturated magnetic induction. Moreover, they must have a narrow hysteresis loop. The soft magnetic materials generally have poor mechanical properties at elevated temperatures. Many industrial applications (e.g., rotors in high-speed generators, magnetic bearings in engines, auxiliary power units, etc.) require soft magnetic materials, which not only can retain their soft magnetism at high temperature but also can withstand high stress at elevated temperatures. ***