The effect of dispersed Ni particles on the microstructure and performance evolution of 3D Ni network reinforced Ag-based contact materials during hot extrusion

Abstract

A microstructure-controllable Ag-Ni composite in plastic deformation is of great significance to its mechanical and electrical performance. In this study, AgNi sintered ingots reinforced with 10 wt% of a continuous three-dimensional (3D) Ni network and different quantities of dispersed Ni particles were prepared. Subsequently, AgNi composites were obtained by hot extrusion at 800 °C. The 3D Ni network was initially elongated in the axial direction and then fragmented in the radial direction, accompanied by the formation of Ni belts with {110}<111> texture and the development of a Ag/<100> texture. However, at high true strains, the Ni belts were recrystallized into spindle/tadpole shapes. The Ni particles dispersed in Ag-rich matrix improved the elastic modulus of the Ag-rich matrix via the mixing rule, grain refinement, and dislocation pile-up, resulting in enhanced load transfer and cooperative deformation between the Ag-rich matrix and the Ni network. Therefore, the addition of a small quantity (0.5 wt%) of dispersed Ni particles is beneficial for obtaining Ag-based electrical contact materials reinforced with long Ni belts (1200–1800 μm in length and ∼20 μm in thickness), which exhibit a low mass loss (2.02 mg) after 100,000 contacts at 24 V/10 A of direct current.