Microstructural Evolution and Performance of In-situ Ag-Ni Composite after Solidification under Electromagnetic Stirring and Deformation

The effect of electromagnetic stirring (EMS) on microstructure and performance of Ag-8 mass% Ni composite was investigated under both solidified and deformed conditions. Without EMS, the Ag matrix formed short, thick dendrites in the ingot; whereas with EMS, dendrites were long and slim. Ni phase mainly formed particles or ribbons, distributed along boundaries between dendrite arms. Cold drawing of the solidified Ag-Ni ingots, both with and without EMS, produced high strength in-situ metal-matrix composite (MMC) consisting of Ag matrix reinforced by Ni ribbons. EMS improved the ductility of the composite, consequently enhancing its drawability and strength. EMS also increased the electrical conductivity in both solidified ingots and deformed in-situ composite wires. In both cases, hardness and tensile strength remained high. A model based on a combination of the modified linear rule of mixtures and the Hall-Petch relationship was used to rationalize the tensile strength and hardness with respect to its fabrication parameters and the microstructure of Ag-Ni in-situ composite.