Mechanical and magnetic characterisation of SiC whisker reinforced Fe–Co alloy composites

SiC whisker reinforced Fe–Co composites containing up to 3 vol% of bare, copper, Ni–P and cobalt plated whiskers were prepared in a spark plasma sintering furnace at 900 °C, applying a pressure of 80 MPa for 5 min. The influences of the bare and the coated whisker additions on the magnetic and mechanical properties of the brittle matrix were assessed and correlated using their microstructural and fractographic observations. The bare whiskers played dual and contradicting roles on the grain growth behaviour of Fe–Co. The insulating fibres, which promoted grain growth of Fe–Co by concentrating the sintering current in the regions away from them, reduced the grain growth kinetics by pinning the boundaries. The grain growth was more pronounced in all the materials with more than 2 vol% of whiskers. Among the coatings investigated, the amorphous Ni–P coating aided to achieve maximum improvements in both strength and ductility by forming nanocrystalline intermetallic compounds with Fe–Co and by promoting dispersion of the whiskers in the matrix alloy. The copper and cobalt coatings were not beneficial in improving the mechanical properties of the composites because of their inability to promote homogeneous dispersion of the whiskers and to form new intermetallic compounds with the matrix alloy, respectively.