Silver Matrix Composite Reinforced by Aluminium-Silver Intermetallic Phases

Abstract

Silver and aluminum powders (82 mass % Ag and 18 mass % Al) were mixed and hot extruded at 673 K with extrusion ratio λ = 25. Performed X-ray diffraction analysis of as extruded rod revealed the development of Ag 3 Al and Ag 2 Al-type intermetallic phases. Structural observations and both chemical and diffraction analysis of structural components confirmed the growth of mentioned phases in the vicinity of elementary Al and Ag granules. No pores or voids were observed in the material. Mechanical properties of the composite, UTS = 490MPa, YS = 440 MPa, HV2 = 136, were relatively high if compared to commercial Ag and Cu products. Hot compression tests pointed to the good hot workability of the composite at deformation temperature range 473 K -773 K.The differential scanning calorimetry tests were performed in order to estimate structural processes during heating of Ag/ Al composite that lead to thermodynamically stable liquid state. It was found that characteristic temperature of three endothermic peaks correspond to (1) peritectoid transformation μ-Ag 3 Al → ζ-Ag 2 Al + (Ag), (2) the eutectic melting ζ-Ag 2 Al + (Al) → L, (3) melting of the ζ-Ag 2 Al phase.The Vickers hardness of the samples annealed at 673 K, for the time range up to 6900 minutes, was also determined. It was concluded that mutual diffusion of elements between Ag and Al granules and the growth of μ-Ag 3 Al and ζ-Ag 2 Al grains during annealing at 673 K result in a slight hardening of the composite.