Preparation of mono-sized fe-based metallic glass micro particles by pulsated orifice ejection method and evaluation of the particles

The mono-sized [(Fe_0.5Co_0.5)_0.75B _0.2Si_0.05]₉₆Nb₄ metallic glass micro spherical particles with narrow size distribution and high sphericity have been successfully prepared by Pulsated Orifice Ejection Method (POEM). The desired size of particles can be formed by adjusting process parameters, such as the rod displacement, the time for reaching the pulse voltage from zero voltage, the applied pressure and so on. The glassy fraction determined by enthalpy released for the particles during continuous heating in DSC, based on 70.23 J · g"1 as the enthalpy released of a fully amorphous particle (as proved by X-ray diffraction), shows that the changes of phase in one particle from single amorphous phase to amorphous crystalline mixed phase and then overall crystalline occur within the range of 350 mm and 400 mm in diameters. The critical cooling rate for the occurrence of crystalline in single amorphous phase is estimated to be within the range of 700 and 800 K · sec"1, which is slightly lower than that measured by time-temperature transformation diagram of the bulk metallic alloy, and supposed to be affected by the initial temperature of the melt.