Quasiperiodic and Frank-Kasper phases formation during primary crystallization of Fe-base amorphous alloys

Initial stages of devitrification were investigated for iron based amorphous alloys: Fe-P-C-(Cr, Mn, Mo); Fe-B-Si-Nb with 67 - 80 at.% of Fe and 15-25 at.% of P+B+Si+C. Primary precipitated phases of α-Mn or related tetrahedrally close packed structure types, in particular aperiodic structures, were observed. They are characterized by fast nucleation and formation of nanostructures. In some cases specific precrystallization state is formed for which diffraction patterns are consistent with the existence of nano-clusters with local TCP structure. Structure of the liquid or amorphous state can be presented as composition of the same clusters but with the different, noncrystallographic long range order