Densification mechanism of Zr-based bulk metallic glass prepared by two-step spark plasma sintering

In this work, a two-step spark plasma sintering process for amorphous alloys was proposed. Densification mechanisms and the effects of the pretreatment process on the microstructure and mechanical properties were studied. The results show that the two-step spark plasma sintering process could significantly improve the density and fracture strength of sintered samples and even reduce the final sintering temperature. The lower-temperature pretreatment process resulted in higher density and more uniform density distribution of the powder billets, which reduced the temperature gap between inside of the powder particles and the contacts, as well as reducing the electrical resistivity of the powder billets. Starting from highly homogeneously packed powder billets, more current flowed to the powders, promoting the discharge effect and internal Joule heat generation. The pre-treated high-quality powder billets enhanced the sintering process, which enabled the realization of a high strength and reduced sintering temperature. (C) 2020 Elsevier B.V. All rights reserved.