Soft Magnetic Cu-Co-Ni Composite Materials Produced byMechanical Alloying, Cold Compaction, and Sintering

摘要

Nanostructured Cu-(90)Co-(10) and Cu-(85)Co-(10)Ni-5 soft magnetic alloys were obtained by mechanical alloying in a planetary mill. Ultrafine Co and (Co.Ni) particles were obtained and dispersed in the copper powder matrix, thus affecting the magnetic properties of the as-milled powder obtained from the non-equilibrium phases synthesis. The powder alloys were characterized by means of X-ray diffraction, SEM, HRTEM, and EPMA. The magnetic properties of the powder alloys measured at 300K as a function of milling time reveal that the Cu-Co-Ni alloys show a superparamagnetic behavior. The hardness and magnetic properties of Cu-Co and Cu-Co-Ni alloyed powders reached their optimum values after milling for 60h. Both of the alloy powder blends milled for 60h were cold compacted and sintered at 973K for 1h. The effect of nickel on the Ni-5Co-xCu-(95-x) system can be explained as Ni content inhibits the two-solid (Cu-Co) phases segregation in the alloys when annealed at high temperature, leading to a structure with less Co particles precipitation into an homogeneous Cu-Ni strengthened solid solution matrix, as evidenced by the 441 MPa hardness. The variation of magnetic properties and its dependence on the structure/ precipitation change with milling time for each alloy are discussed.