High magnetic permeability in a Ni-Fe-Cu-Mo alloy made by powder metallurgy

The initial permeability of high-permeability alloy sheet rolled from sintered compacts is substantially increased by sintering for times longer than are currently used. Complete alloying of copper does not take place in a compact using a conventional sintering time; sheet rolled from such a compact has a banded microstructure so that the material is slightly inhomogeneous. An upper limit to the initial permeability of such sheet is probably set by internal strains caused by local variations in the lattice parameter.