The solidification microstructure of the master alloys (MAs) and slowly cooled alloys (SCAs) for Mg-Cu-Gd ternary system and the best glass former in Mg-Cu-Ag-Gd quaternary system were systematically investigated. the best ternary glass former alloy, Mg61Cu28Gd11, with a critical size (D-c) of 12 mm is correlated with a eutectic reaction L -> Mg2Cu + Mg3CuGd in Mg-Cu-Gd equilibrium phase diagram. And a phase diagram was established for the studied compositions in the Mg-Cu-Gd ternary system. The glass forming ability (GFA) was dramatically improved when Cu is substituted by Ag. In Mg-Cu-Ag-Gd quaternary system, the critical size reached 27 mm for Mg59.5Cu22.9Ag6.6Gd11 and this is the largest D-c for all reported Mg-based bulk metallic glasses (BMGs). The reasons why the Mg59.5Cu22.9Ag6.6Gd11 has an extraordinary glass forming ability was explained from two aspects: stabilization of the liquid and frustration of the competing phase.
部门归属
[zheng, qiang] chinese acad sci, shenyang natl lab mat sci, inst met res, shenyang 110016, peoples r china. [zheng, qiang] china acad ordnance sci, ningbo branch, ningbo 315103, zhejiang, peoples r china.;zheng, q (reprint author), chinese acad sci, shenyang natl lab mat sci, inst met res, 72 wenhua rd, shenyang 110016, peoples r china.;qiangzheng616@hotmail.com
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