Microstructure Evolution of Cu_xNi₃Fe₁(x=4~12) Alloys

In order to study the effect of the microstructure on the properties of Cu-Ni-Fe alloy, in the present paper, the Cu_xNi₃Fe₁ (x=4, 7, 9, 12) alloys with the fixed Ni:Fe atom ratio and varying Cu content were prepared.Then the composition and evolution of the phase were characterized by XRD and SEM.The results show that the spinodal decomposition is the main strengthening mechanism in these alloys.With the increase of Cu content, tensile strength, yield strength and hardness decreased due to the decreased of Ni-Fe riched phase.The lath-shaped precipitation showed better corrosion resistance owing to its high packing density.During the aging process of the Cu_xNi₃Fe₁ (x=4, 7, 9) alloys, a small amount of γ'-Ni₃Fe was precipitated, which had no obviously effect on the properties of the alloy.The γ'-Ni₃Fe phase decompose at about 500℃, resulting in a slight decrease in the resistivity.In addition, a large number of-Fe were precipitated in the grain boundaries when x=12.