Bell Telephone Laboratories

At&t Bell Laboratories

At&t Technologies, Inc.

Jack H Wernick

Richard C Sherwood

Gilbert Y Chin

Sungho Jin

Martin L Green

Chester M Bordelon

Chester M Boredelon

Disclosed are magnetically soft ferritic multiphase Fe-Cr-Ni alloys containing at least about 82 weight percent Fe, between about 3 and about 10 weight percent Cr, and between about 2 and about 8 weight percent Ni, a method for producing such alloys, and devices comprising such an alloy body. The method comprises a low-temperature anneal in the (.alpha.+.gamma.) region of the Fe-Cr-Ni phase diagram. Inventive alloys typically have a coercive force H.sub.c no more than about 3.0 Oe, preferably no more than about 2.0 Oe, a maximum permeability .mu..sub.m of at least about 1500 G/Oe, preferably at least about 2500 G/Oe, and contain at least about 5 volume percent non-.alpha.-phase material, typically .alpha.'- and .gamma.-phase material. Inventive alloys typically also have yield strength to 0.2% offset of at least about 26.10.sup.7 Pa (40.10.sup.3 psi), elongation to fracture of at least about 15%, good formability and rust resistance. 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, recording heads, pole pieces, and armatures.

Magnetically soft ferritic Fe-Cr-Ni alloys

Disclosed are magnetically soft ferritic multiphase Fe-Ni alloys having a Ni content in the range of about 4 to about 16 weight percent, devices containing a body fabricated from such alloys, and method for heat treating such body. Appropriate heat treatment comprises a low-temperature anneal in the two-phase (.alpha.+.gamma.) region of the Fe-Ni phase diagram, and typically results in improved magnetic properties. In particular, alloys according to the invention having x weight percent of Ni have a maximum permeability .mu..sub.m at least as large as 1.5[25(16-x).sup.2 ]G/Oe. The alloys typically also have a coercive field H.sub.c at most as large as 0.7[0.65(1+0.6x)]Oe, a saturation induction B.sub.s 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 40 10.sup.3 psi, 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.

Ferritic Fe-Ni magnetic alloys

In view of rising cobalt costs, low-cobalt alloys such as, e.g., Fe-Cr-Co alloys are finding increasing use in the manufacture of permanent magnets. Desired magnetic energy product of such magnets is typically at least 1 million gauss-oersted. In the interest of maximizing magnetic energy product per unit weight cobalt, low-cobalt Fe-Cr-Co alloys are processed by solidifying a bulk object from a melt, annealing, quenching, and aging by cooling at rates in a range of 0.1 to 2 degrees C. per hour in a magnetic field. Cold working prior to aging may be used to further enhance magnetic energy product. Resulting magnets have optimized maximum magnetic energy product (BH).sub.max per unit weight cobalt comprised in an alloy.

Low-cobalt Fe-Cr-Co permanent magnet alloy processing

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Madison, NJ, United States of America

Jack H Wernick