Abstract: Relaxation behavior of Ca60Mg20Zn20, Ca60Mg20Cu20, Ca65Mg15Zn20, Ca50Mg20Cu30, and Ca55Mg18Zn11Cu16 bulk metallic glasses was determined in the glass transition region using DSC with the heating rates from 1 to 160 K/min. The activation enthalpy of structural relaxation and the fragility index m were found to be smaller in the glassy state (onset of the glass transition) than in the supercooled liquid state (end of glass transition). The Ca-based glass-forming liquids showed strong behavior of the relaxation time, with the fragility indexes m in the range of 33 to 40. The strong liquid behavior implies sluggish kinetics of crystallization in the supercooled liquid region and explain the very good glass forming ability of these alloys. The critical cooling rate for amorphization Rc of the Ca-based bulk metallic glasses was estimated to be in the range of 0.3 to 10 K/s, which is similar to Rc values for the best Pd and Zr based metallic glass forming alloys discovered so far.
| Limitations: |
 APPROVED FOR PUBLIC RELEASE |
| Description: |
Journal article preprint |
| Pages: |
29 |
| Report Date: |
Apr-2009 |
| Contract Number: |
FA8650-04-D-5235 FA865004D5235 |
| Report Number: |
A101205 |
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