STRUCTURES AND SUPERPARAMAGNETIC PROPERTIES OF OVERAGED Fe-Al-Mn-C ALLOYS

摘要

Microstructures and superparamagnetic properties in aged-hardened Fe-9Al-30Mn- (x)C,Si alloys, resulting from overaging at a temperature of 823 K for 48 h to 313 days, have been investi- gated by transmission electron microscopy (TEM), X-ray diffraction patterns, and vibrating sample magne- tometry (VSM). The results reveal that the precipitate K-phase [(Fe,Mn)_3AlC] decomposition in this alloy, overaged at 823 K for one week, resulted from two separate mechanisms: (1) wetting of the l/2α_0'(100) antiphase boundary segment (APBs) of D0-3 [(Fe/Mn)_3Al] domains by the B2 [(Fe/Mn)Al] phase, and (2) precipitation of the B2 [(Fe/Mn)Al] phase within the domain. A superparamagnetic behaviour was discov- ered when the alloy was overaged at 823 K for ≈120-313 days. The super-soft magnetic property was mainly attributable to the ferromagnetic spinel-ordered (B2 [(Fe/Mn)Al]+D0_3 [(Fe/Mn)_3Al]) phases and ordered B2 with monoclinic α′Mn structures.