Synthesis of Fe Based Metallic Glass–Pd Based Metallic Glass Composite by Slightly Pressured Liquid Phase Sintering

Abstract

To consolidate [(Fe_0.5Co_0.5)_0.75Si_0.05B_0.2]₉₆Nb₄ metallic glass powder to full density, a pressurized liquid phase sintering was employed, which was intended to promote densification by an enhanced wetting of a liquid phase with solid particles. Pd_42.5Ni_7.5P₂₀Cu₃₀ metallic glass powder, which has been reported to have a high glass forming ability and the lowest critical cooling rate of glass formation of 0.067 K/s, was chosen as a liquid phase component. The melting point of the Pd_42.5Ni_7.5P₂₀Cu₃₀ metallic glass alloy of 763 K is lower than the glass transition temperature of the [(Fe_0.5Co_0.5)_0.75Si_0.05B_0.2]₉₆Nb₄ metallic glass alloy of 808 K. However, the wettability of this alloy with the Pd_42.5Ni_7.5P₂₀Cu₃₀ alloy was revealed to be poor. Therefore, sintering pressure was applied to the compacts to promote a viscous flow deformation of solid particles and also to enhance the intergranular permeation of the liquid phase. A specially designed micro-hot press was devised for the pressure-sintering experiment. A pseudo-wettability was observed during pressure-sintering, and the liquid phase was found to fill completely the intergranular space of the powder compact. The relative density of 64–95%, as well as the sintering structure, could be controlled by the punch displacement to squeeze out a part of the liquid phase from the compact. The compressive fracture strength of the obtained metallic glass composite was found to be as high as 2051 MPa, and the fracture was observed to be intragranular type, suggesting a good bonding in the particle-binding phase interface.