Crystallization evolution and relaxation behavior of high entropy bulk metallic glasses using microalloying process

Abstract

The role of the microalloying process in relaxation behavior and crystallization evolution of Zr20Cu20Ni20Ti20Hf20 high entropy bulk metallic glass (HEBMG) was investigated. We selected Al and Nb elements as minor elements, which led to the negative and positive effects on the heat of mixing in the master HEBMG composition, respectively. According to the results, both elements intensified β relaxation in the structure; however, α relaxation remained stable. By using different frequencies in dynamic mechanical analysis, it was revealed that the activation energy of β relaxation for the Nb-added sample was much higher, which was due to the creation of significant structural heterogeneity under the microalloying process. Moreover, it was found that Nb addition led to a diversity in crystallization stages at the supercooled liquid region. It was suggested that the severe structural heterogeneity in the Nb-added sample provided multiple energy-level sites in the structure for enhancing the crystallization stages.