A structural steel which possess both high strength and high toughness and has particular application of cryogenic uses. The steel is produced by the utilization of thermally induced phase transformation following heating in a three-phase field in iron-rich alloys of the Fe-Ni-Ti system, with a preferred composition of 12% nickel, 0.5% titanium, the remainder being iron.
This is a continuation of application Ser. No. 466,346, filed May 2, 1974, now abandoned, which constituted a division of application Ser. No. 249,585, filed May 2, 1972, now U.S. Pat. No. 3,836,407 issued Sept. 17, 1974.
Magnetically actuated devices such as, e.g., switches and synchronizers typically comprise a magnetically semihard component having a square B-H hysteresis loop and high remanent induction. Among alloys having such properties are Co-Fe-V, Co-Fe-Nb, and Co-Fe-Ni-Al-Ti alloys which, however, contain undesirably large amounts of cobalt. According to the invention, devices are equipped with a magnetically semihard, high-remanence Fe-Ni or Fe-Ni-Mn alloy which contains Ni in a preferred amount in the range of 6-20 weight percent and Ni in an amount which is less than or equal to 8 weight percent. Remanence B.sub.r (gauss) is greater than or equal to 15,000 gauss; squareness B.sub.r /B.sub.s typically is greater than 0.95. Magnets made from alloys of the invention may be shaped, e.g., by cold drawing, rolling, bending, or flattening and may be used in devices such as, e.g., electrical contact switches, hysteresis motors, and other magnetically actuated devices. Preparation of alloys of the invention may be by a treatment of producing fine-scale, essentially isotropic, two-phase structure, subsequent uniaxial deformation, and aging to achieve a fine-scale, elongated, and aligned two-phase or multiphase structure.
