The present study investigates the effects of a minor addition (MA) of alloying elements to Mg 65Cu 25Gd 10 bulk-forming metallic glass (BMG). First, we show that a MA of Y or Ca that has singular positive enthalpy of mixing relationship (PEMR) with a constituent element in Mg 65Cu 25Gd 10 BMG leads to an improvement in plasticity as well as glass-forming ability (GFA) in a limited composition range. Second, we show that a MA of Co with plural PEMRs and a large negative enthalpy of mixing relationship (NEMR) to Mg 65Cu 25Gd 10 BMG drastically deteriorates both GFA and plasticity due to large variation of matrix composition. Finally, the paper demonstrates that a MA of Be that has unfavorable mixing relationships with all constituent elements has no adverse effect on GFA and precipitates Be-rich secondary nanocrystals in the amorphous matrix, which leads to improved plasticity up to ε f = 3.41 ± 0.10% in (Mg 65Cu 25Gd 10) 95(Be) 5 BMG. Consequently, our results suggest that a MA of a 4th alloying element with PEMR to Mg 65Cu 25Gd 10 BMG can result in different degrees of heterogeneity in the amorphous matrix depending on the overall combination of mixing enthalpies among atomic pairs, which significantly influences the plasticity as well as GFA of the BMGs.
Bibliographical noteFunding Information:
This work was supported by the Global Research Laboratory of the Korean Ministry of Science and Technology. One of the authors (E.S. Park) was supported by Basic Science Research Program through the National Research Foundation funded by the Ministry of Education, Science and Technology ( NRF-2009-0077096 ) and Engineering Research Institute at Seoul National University .
All Science Journal Classification (ASJC) codes
- Mechanics of Materials
- Mechanical Engineering
- Metals and Alloys
- Materials Chemistry