Liquid phase separation in immiscible Ag–Ni–Nb alloy and formation of crystalline/amorphous composite

Phase decomposition in liquid miscibility gap presents a unique opportunity for designing amorphous/crystalline composites with a multilayer structure. One of typical monotectic systems, Ag-Ni alloy, is selected, and element Nb is added in the Ag-Ni alloy. The new ternary Ag-Ni-Nb monotectic alloys are rapidly quenched by using melt spinning technique. It is revealed that the ternary alloy undergoes a liquid-liquid phase decomposition and forms two immiscible Ag-rich and NiNb-rich liquids. Subsequently, the immiscible liquids solidify into Ag-rich crystalline and NiNb-based amorphous phases, respectively. Self-assembled amorphous/crystalline composites with double layer and sandwich type structures have been developed. The structure of the alloy ribbons with a dependence on the composition changes from a particle-dispersed structure to double layer structure and to sandwich type structure. The phase formation and thermal property of the quenched alloys are investigated. The formation mechanism of the crystalline/amorphous composite structures has been discussed. (C) 2011 Elsevier B.V. All rights reserved.