Effect of Ag micro-alloying on the microstructure and properties of Cu–14Fe in situ composite

Abstract

This paper studied Ag micro-alloying in the deformation-processed Cu–14Fe in situ composite, by a comparison of Cu–14Fe and Cu–14Fe–0.06Ag. Each alloy was prepared by casting and processed into an in situ composite by hot and cold working. The microstructures were documented using light microscopy and scanning electron microscopy (SEM). The mechanical properties were measured with a tensile-testing machine. The electrical conductivity was measured with a micro-ohmmeter. For both alloys, the as-cast microstructure consisted of a Cu matrix and Fe dendrites; after hot and cold working the microstructure consisted of a Cu matrix containing Fe fibres elongated in the working direction. The as-cast Ag-containing alloy contained finer Fe dendrites. The Ag-containing in situ composite had thinner Fe fibres, higher tensile strength, higher ductility, and higher conductivity. The cold worked Cu–14Fe–0.06Ag in situ composite with cumulative cold deformation strain η=7.8 (where η=ln(A0/A) and A0 and A are the original and final cross-section areas, respectively), achieved a tensile strength of 930MPa and a conductivity of 56%IACS (International Annealed Copper Standard; 17.241nΩm is defined as 100%IACS). The Ag micro-alloyed in situ composite had a combination of properties comparable to that of a much more expensive alloy containing much more Ag. After 1h heat treatment at 300°C, the tensile strength was increased to 950MPa and the conductivity was increased to 56.4%IACS.