Microstructure and strength of Cu–Fe–Ag in situ composites

Three Cu–Fe–Ag in situ composites, i.e. Cu–14 wt.%Fe–1 wt.%Ag, Cu–14 wt.%Fe–3 wt.%Ag and Cu–11 wt.%Fe–6 wt.%Ag were prepared by cast and drawn process. Microstructure evolution and mechanical properties of the composites were investigated. The results show that the presence of Ag can strengthen the composite and the fracture surfaces of Cu–Fe–Ag composites exhibit shear characteristics at lower draw ratio. The ultimate strength of the above three Cu–Fe–Ag composites reached 1119 MPa, 1578 MPa and 1357 MPa in sequence at draw ratio η = 6.1, however that of the same processed Cu–12 wt.%Fe is only 978 MPa. The higher strength of Cu–Fe–Ag results from the strengthening effect of Ag: (1) refining the primary Fe dendrites and reducing the spacing between the filaments; (2) solution and precipitation strengthening the copper matrix and (3) strengthening the composite in the form of aligned Ag filaments if the amount Ag is enough for the formation of Cu–Ag eutectic under certain solidification conditions.