Interpretation of densification behavior of spark plasma sintered Fe-based metallic glass powders from the standpoint of internal friction

In this study, Fe-based bulk metallic glass (BMG) was fabricated using spark plasma sintering (SPS) method and compacts with various densities were obtained at different temperature. To better understand the densification process of metallic glass powders, internal friction was employed to study the internal structural evolution as a function of temperature. Three stages were found in the dynamic relaxation spectroscopy, and exhibited mechanical behavior was closely related to the densification process. By further analyzing relaxational dynamics using Quasi Point Defects (QPD) theory, the correlation factor chi which is indicative of atomic mobility was calculated. The results showed that chi increased sharply above T-g, suggesting intensified atomic motion in super-cooled liquid region (SLR). Furthermore, chi reaches peak value at two adjacent crystallization peak respectively, indicating the feasibility of improving compact density at second crystallization temperature range above SLR. The combination of strengthened atomic motion induced activated diffusion and superplastic deformation of MG powders in SLR facilitated densification of MG powders concurrently. (C) 2019 Elsevier B.V. All rights reserved.