DEVICES COMPRISING A BODY OF FE-NI MAGNETIC ALLOY

DEVICES COMPRISING A BODY OF A Fe-Ni MAGNETIC ALLOY This invention relates to magnetically soft Fe-Ni alloys having a Ni content in the range of about 4 to about 15 weight percent, and devices comprising a body comprising such alloys. Appropriate heat treatment of the alloys, typically comprising a low-temperature anneal in the twophase (.alpha.+.gamma.) region of the Fe-Ni phase diagram, can yield improved magnetic properties. In particular, alloys according to the invention having x weight percent of Ni have a maximum permeability .mu.m at least as large as 1.5¢25(16-x)2!G/Oe. The alloys typically also have a coercive field Hc at most as large as 0.7¢0.65(1+0.6x)!0e, a saturation induction Bs of at least about 20 kG, a maximum incremental permeability .DELTA..mu., measured with an applied a.c. field of about 0.005 Oe, of at least about 150 G/Oe, and a yield strength to 0.2 percent offset of at least about 40x103psi, with all the material properties measured at room temperature. Alloys according to the invention can advantageously be used in devices comprising a magnetically soft body, for instance in electro-acoustic transducers, e.g., in telephone receivers.