Effects of Cooling Rates and Container Walls in Preparation of Spherical Fe and Pd Based Metallic Glassy Particles

Abstract

  Preparation of Fe-based and Pd-based metallic glassy particles with a diameter of around 500 μm were investigated. Firstly, we measured the critical cooling rate of Pd_42.5Cu₃₀Ni_7.5P₂₀ metallic glass and our results showed that its critical cooling rate was about 0.4 K/s. Pd-based metallic glassy spherical particles with fully amorphous structure were successfully prepared by heating the samples on the Al₂O₃ substrate up to their melting points and cooling under the cooling rate of around 3 K/s. In contrast, [(Fe_0.5Co_0.5)_0.75Si_0.05B_0.2]₉₆Nb₄ metallic glassy particles cannot be prepared by the same process. This seemed to be caused by a reaction between the Fe-based metallic glass and the Al₂O₃ substrate around its melting point. This result suggested that containerless solidification method is expected to be used to prepare Fe-based metallic glassy particles. We successfully prepared mono-sized spherical particles of [(Fe_0.5Co_0.5)_0.75Si_0.05B_0.2]₉₆Nb₄ metallic glass by Pulsated Orifice Ejection Method (POEM) as an ideal process for Fe-based metallic glasses.