Enhancement of plasticity and the occurrence of liquid-state phase separation have been investigated by partially substituting Zr with Y in Cu46Zr47-xYxAl7 (x = 0, 2, 5, 10, 15, 20, 25, 30, 35) alloys. Since Y has a positive enthalpy of mixing with Zr (+35 kJ/mol) in the liquid state, the alloy composition moves to the metastable miscibility gap of the two amorphous phases with increasing Y content. Phase separation into Y-rich and Zr-rich amorphous phases occurs during cooling from the liquid state when the Y content is above 15 at.%. The bulk amorphous alloys consisting of two phase-separated amorphous phases exhibit extreme brittleness, while the single-phase amorphous alloys containing 2-5 at.% of Y exhibit enhanced plasticity because of the introduction of chemical inhomogeneity in the amorphous matrix. The results indicate that the addition of an element having a positive enthalpy of mixing with the constitutive element in bulk amorphous alloys can increase the plasticity as well as the glass-forming ability, but for a limited composition range.
Bibliographical noteFunding Information:
This work was supported by the Creative Research Initiatives of the Korean Ministry of Science and Technology. The authors acknowledge Dr. B.S. Seong at KAERI for performing the HRND experiment and Ms. H.J. Chang at Yonsei University for performing the HRTEM experiment.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Polymers and Plastics
- Metals and Alloys