Effect of Trace Cerium on the As-Cast Microstructure of Ag-Cu-Ni Alloy

Abstract

It is well known that the rare-earth elements (RE) have exhibited favorable microalloying effects on the microstructure and properties of silver alloys. In the present investigation, a detailed description of the microstructure of a Silver-4wt.%Copper-0.3wt.% Nickle as–cast alloy containing 0.2wt. % of a cerium element was presented. Particles types occurring and their distribution in the microstructure, as well as the distribution of elements in the phases were described. The result show that the second phase in Ag-Cu-Ni Alloy is Cu-Ni-rich solution phase, some of which forms interdendritic segregation in Ag matrix as eutectic colonies. Trace additions of cerium to the alloy decrease eutectic proportion and size of the Cu-Ni-rich phase, result in finer and more uniform secondary phases distributed in the α-Ag matrix. Besides Cu-Ni-rich phase, the Ni-Cu-Ce-rich and Ag-Cu-Ce-rich phases were found in the alloy. The Ni-Cu-Ce-rich should be the (NiCu)5Ce, which is distributed as dispersive particle in the Ag matrix, and Ag-Cu-Ce-rich phases should be (AgCu)4Ce, which is distributed as fibrous particle of eutectic colonies. Some of (AgCu)4Ce phases are located at the interface between α-Ag matrix and Cu-Ni-rich phases, which indicate that Ce could be segregated at the frontier of Cu-Ni-rich phases during the growth, causing Cu-Ni-rich phase refinement.