Physical-and-chemical processes at the interfaces of (Cu–Ni–Mn–Fe)/ (W–C) composites
The spontaneous infiltration method for fabricating composites was used, in which molten Cu–Ni–Mn–Fe binders penetrated W–C filler particles due to capillary forces. The metal matrix composites thus obtained were characterized for phase composition, microstructure, porosity and microhardness. All composites were studied in their as-prepared condition with further annealing at 900°С for 60 and 750 h. It was shown that the mechanism based on the dissolution/diffusion bonding of the particulate/matrix interface was in agreement with the results of this study. The interfacial reactions provided a driving force for wetting but did not give rise to unwanted phases that could degrade the properties of the composite materials. From the EDX measurements it was concluded that mainly Fe atoms diffused from the Cu–Ni–Mn–Fe binders into the WC phase of the eutectic (WC+W2C) filler. Dissolution of this phase resulted in the appearance of W2C layer at the interface. Annealing at 900°С significantly promoted the interfacial reaction especially during the first 60 h of heat treatment. The degree of the reaction between the molten Cu–Ni–Mn–Fe alloys and W–C particulate could be limited by controlling the iron content of the binders to obtain an optimal interface.