Highly variable chemical short-range order in a high-entropy metallic glass

作者：Zhang, X.; Luan, H.; Lou, H.; Liang, T.; Chen, S.; Xu, D.; Yin, Z.; Wang, L.; Zeng, J.; Ren, Y.; Zeng, Z.; Shao, Y.; Yao, K. -f.^*; Zeng, Q.^*

来源：Materials Today Physics, 2022, 27: 100799.

DOI：10.1016/j.mtphys.2022.100799

• High-entropy
• Metallic glass
• Chemical short-range order
• Synchrotron radiation

High-entropy metallic glasses (HE-MGs) recently joined the high-entropy materials and metallic glasses families as a novel class of alloys. The high-entropy effect that is believed to be crucial to HE-MGs, however, has not been well explored yet in amorphous forms. In this work, we chose a Zr20Nb20Cu20Ni20Ti20 quinary HE-MG as a model system and studied its structural evolution as a function of temperature by in situ synchrotron high-energy x-ray diffraction (XRD) and extended x-ray absorption fine structure spectroscopy (EXAFS) techniques. The HE-MG exhibits irreversible structural crossover upon heating, specifically, from a relatively disordered high-energy glass state to a more ordered low-energy glass state in the supercooled liquid region but below its crystallization temperature. The pair distribution PDF) derived from XRD and EXAFS data suggests that the highly variable chemical short-range order (CSRO) is the underlying mechanism of the structural ordering crossover in the HE-MG. The initial ribbon sample obtained by melt-quenching has a relatively high chemical disorder with nearly random nearest atomic neighbors due to the high-entropy effect. However, the high chemical disorder is metastable upon post-fabrication heating at medium temperatures, which gradually degrades driven by enthalpy with the random neighbors replaced by more energy-favored ones. The chemical complexity of the HE-MG prevents further development of the ordering into typical crystallizations. In contrast, a conventional quinary MG with a close composition but lower entropy (Vit106, Zr57Nb5Cu15middot4Ni12middot6Al10) does not show similar variable CSRO during heating. These findings demonstrate that the high-entropy effect does play an essential and unique role in HE-MGs. Competitions between entropy, enthalpy, and atomic-level stress could result in high variability in CSRO and properties, which may provide us another unexplored dimension for effectively tuning structures and tailoring properties for various applications.

• 单位
  中国科学院; 北京理工大学; 清华大学