Rapid solidification of silver-rich Ag-Cu-Zr alloys

In this work we explored the possibility of obtaining amorphous/crystalline composites in the Ag-rich side of the Ag-Cu-Zr ternary system exploiting the presence of a miscibility gap in the liquid. Four alloys with nominal composition (at.%) Ag 75Cu 11Zr 14 (alloy A), Ag 73Cu 17Zr 10 (alloy B), Ag 47.5Cu 22.5Zr 30 (alloy C), Ag 47.5Cu 30Zr 22.5 (alloy D) were investigated. The effect of the cooling rate and the composition on phase selection and microstructures was evaluated by comparing slowly cooled master ingots and rapidly quenched ribbons. Evidence of the liquid miscibility gap was observed only in alloys B and D, either in the master ingots and the ribbons. After rapid solidification, partial amorphisation was achieved for alloys C and D, where precipitates of the Ag-rich solid solution, showing various sizes, are dispersed in the amorphous matrix. A significant increase in hardness was achieved in the case of partially amorphous ribbons of alloys C and D (442 HV and 533 HV, respectively). Experimental results are discussed on the basis of the recently reassessed ternary Ag-Cu-Zr phase diagram. © 2011 Elsevier B.V. All rights reserved.