Characterization of as-synthesized and mechanically milled Fe–Al powders produced by the self-disintegration method

Structural evaluation morphologies, chemical-phase compositions, microhardness and ordering transformation of as-disintegrated and mechanically milled Fe–Al powders were studied. The underlying mechanism principles of the self-disintegration process in the powder production, based on a natural phenomenon of the self-disintegration of the high aluminium cast iron, are presented in this work. The self-disintegration process affects diverse morphology and dimensional heterogeneity of the ordered B2 FeAl particles with the size range of 50–125 μm. The particle morphology as well as the crystalline size and long-range order (LRO) of B2 FeAl phase were changed as a result of milling. As-milled particles possess a nanocrystalline structure based on B2 FeAl solid solution with significantly smaller ordering and crystallite size of about 8 nm after 20 h of milling. Even though the disordering of the secondary solution reduced the particle strengthening, it is compensated by the strengthening originating from the crystallite fragmentation, such that microhardness increase is negligible with milling time extension. The formation of nanograins in the self-disintegrating powder particles allows one to assume that this microstructure will be inherited in the Fe–Al type coatings sprayed by a GDS method. The milled self-disintegrating Fe–Al type powders were used in the gas detonation (GDS) process to obtain the nanocrystalline coatings with a composite-like structure containing oxide phases which were formed in-situ during a GDS process.