In-situ study of FeCoCrMoCBTm high entropy bulk metallic glasses with high thermal stability via high-energy synchrotron X-ray diffraction

Fe-based bulk metallic glasses (BMGs) exhibit good potential application in magnetic-electrical parts and anticorrosion scenarios due to the good soft magnetic and mechanical properties. Despite their good properties, Fe-based BMGs generally suffer from the crystallization from a metastable glass state via structural relaxation, nucleation, and grain growth upon heating. Thus, pursuing high thermal stability is essentially the holy grail of the BMG research community. In this work, we successfully developed a series of FeCoCrMoCBTm high entropy BMGs (HE-BMGs) with superior thermal stability via microalloying and entropy tuning. Among these developed alloys, the Fe33Co15Cr17Mo13C15B6Tm2 HE-BMG exhibits the best thermal stability with crystallization temperature exceeding 900 K (916 K) and activation energy of 510.3 +/- 30 kJ/mol, which is higher than most of the conventional metallic glasses (MGs). The in-situ high energy synchrotron X-ray diffraction of Fe33Co15Cr17Mo13C15B6Tm2 HE-BMG upon heating was carried out to further clarify the phase transformation mechanism and its correlation to thermal stability. This study offers some important insights into the crystallization path and thermal stability of HE-BMGs.