TEM study and magnetic measurements of precipitates formed in Cu-Fe-Ni alloys.

The precipitation behavior of Cu-Fe alloys with Ni addition on isothermal annealing at 878 K was investigated by means of transmission electron microscopy (TEM), electron dispersive X-ray spectroscopy (EDS), and field-emission scanning electron microscopy (FE-SEM). Magnetic element atoms were segregated from the solid solution in supersaturated state, and nano-scale magnetic particles were randomly formed in the copper matrix at the initial stage of annealing at 873 K. With increasing the isothermal annealing time, however, the striking feature that two or more nano-scale magnetic particles with a cubic shape aligned linearly along (100) directions were observed upon the isothermal annealing at 873 K. To investigate the relationship between micro-structures and magnetic properties of the heterogeneous Cu-Fe-Ni alloys, magnetic measurements such as M-H measurements were also carried out, using a superconducting quantum interference device (SQUID) magnetometer. In this study, it was revealed that the magnetic properties of the specimen presented the ferromagnetic behavior, during the precipitation process in a Cu-Fe-Ni alloy.