Medium range ordering and its effect on plasticity of Fe-Mn-B-Y-Nb bulk metallic glass

Glass formation, thermal properties and mechanical behavior were investigated in a series of Fe65-xMn13B17Y5Nbx (x = 0, 3, 5 and 7) alloys. Appropriate partial substitution of Fe by Nb in a Fe65Mn13B17Y5 bulk glassy alloy simultaneously enhances the glass-forming ability and the mechanical properties of the alloys. The Nb-containing glassy alloys exhibit an additional exothermic event in the supercooled liquid region. This exothermic reaction is correlated with the formation of medium range ordered (MRO) clusters originated from the large difference in mixing enthalpy between constituent elements such as Nb-Y (+30 kJ/mol) and Nb-B (-39 kJ/mol). The presence of MRO clusters in the as-cast state is dependent on the cooling condition from the liquid state, and plays a crucial role in providing plasticity in as-cast Fe-Mn-B-Y-Nb bulk metallic glass.