Abstract
This investigation reports on a scanning electron microscopy (SEM) and transmission electron microscopy (TEM) study of fine particle morphologies formed in Fe–9Al-xMn-y (C, Si) alloys overaged at 823 K from 13 h to 120 d. The results reveal that the fine particle morphologies come from the lamellar structures due to a phase transformation. Two structures are contained in the fine particle morphologies, one is the ordered B2 phase with monoclinic α′Mn structure, the other is the ferromagnetic spinel ordered (B2+D03) structures precipitated from the (γ+κ) matrix. A superparamagnetic behaviour was discovered, as the alloy overaged at 823 K for 120 d. The super soft magnetic property of the specimen is mainly attributable to the fine particle morphologies, which consist of the ferromagnetic spinel ordered (B2+D03) phases and ordered B2 with monoclinic α′Mn structures.
