METHOD OF MANUFACTURE OF AMORPHOUS TRANSDUCER ELEMENTS

Abstract: The present invention relates to a method for manufacturing amorphous transducer elements with a high magnetomechanical coupling and with various non-planar cross-sectional shapes. According to the invention the amorphous strip or ribbon is arranged in a shaping fixture and is annealed in a two-step process with an intermediate cooling step, the annealing process during the first step being carried out with the strip or ribbon firmly fixed in the fixture but with no influence from any magnetic field, and the annealing process during the second step being carried out at a higher temperature with the strip or ribbon no longer being fixed in the fixture and under the influence of a transverse magnetic field.

Description: Method of manufacture of amorphous transducer elements The present invention relates to a method for manu¬ facturing amorphous transducer elements with a high magnetomechanical coupling and with various non-planar cross-sectional shapes. A well known fact is that amorphous magnetic strips, such as ribbons, wires, etc., can be made into transducer elements with a high magnetomechanical coupling by heat- treating or annealing the strip or the ribbon in a trans¬ verse magnetic field. For instance, see IEEE Transactions on Magnetics, Vol. MAG-17, NO. 6 , November 1981: "Magneto¬ mechanical Coupling and Permeability in Transversely An¬ nealed Metglas 2605 Alloys" . The accepted procedure is to place the un-annealed strip in a vacuum or argon-filled furnace and anneal the strip at a temperature of 380°C to 430°C. In this temperature range an atomic motion occurs, but the material maintains its non-crystalline structure. During the annealing process a magnetic field is applied, which is sufficiently strong to develop magnetic domains, and the axes of which are perpendicular to the strip. A difficulty arises when it is desired to give the magnetic strip a particular cross-sectional shape and at the same time achieve a high magnetomechanical coupling. The ideal design is a thin ribbon with an arched cross- sectional shape. If the ribbon for this purpose is placed in a two- part fixture forming the strip to the desired shape, the fixture inevitably generates undesired forces in portions of the strip, generally along the edges. The stresses caused by the fixture unfortunately prevents the develop- ment of domain configurations with a high coupling factor during the annealing process. The result is a substantially reduced coupling factor. Until now, the difficulties described above have lim¬ ited amorphous magnetoelastical strips or ribbons to planar thin strips or ribbons, which due to their flexibility and lack of stiffness have caused difficulties when the strips are being used in certain applications. According to the present invention a method is pro¬ vided that renders it possible to manufacture amorphous magnetic strips or ribbons with any desired non-planar cross-sectional shape, while achieving a high magneto¬ mechanical coupling. In the method according to the invention the strip annealing process is divided into two steps, fixture tension being released between the two steps. An application of the method according to the inven¬ tion, which has proved successful, comprises the following steps : a) The strip or ribbon is arranged in a two-part fix- ture adapted to give the strip the desired cross-sectional shape, the fixture then being closed and the strip, firmly fixed inside the fixture, being exposed to an annealing process at a temperature of around 360°C, without influence from any magnetic field during the annealing process. b) After the annealing process has been completed ac¬ cording to step a) , the fixture and the strip are cooled. c) After the cooling the upper part of the fixture is removed, and the strip, now resting on the lower part of the fixture, is exposed to a second annealing process in the temperature range between 380°C and 430°C, a transverse magnetic field sufficiently strong to develop a domain structure with a high coupling factor being applied in a manner known per se during the annealing process. The resulting product is a transducer element with a high magnetic coupling and with the desired shape.

Claims: CLAIMS 1. Method for manufacturing amorphous transducer elements with a high magnetomechanical coupling and with various cross-sectional shapes, c h a r a c t e r i z e d in that the amorphous strip or ribbon is arranged in a shaping fixture and is annealed in a two-step process with an intermediate cooling step, the annealing process of the first step being carried out with the strip or ribbon firmly fixed in the fixture but with no influence from any magnetic field, and the annealing process of the second step being carried out at a higher temperature with the strip or ribbon no longer being fixed in the fixture and under the influence of a transverse magnetic field. 2 . Method according to claim 1 , c h a r a c t e r ¬ i z e d in a) that the strip or ribbon is put into a two-part fixture adapted to give the strip or ribbon a desired cross-sectional shape, the fixture then being closed and the strip, firmly fixed inside the fixture, being exposed to an annealing process at a temperature of approximately 360°C, b) that the fixture and the strip are cooled down af- ter the annealing process of a) having been completed, and c) that after the cooling, the upper part of the fix¬ ture is removed, and the strip or ribbon, now resting upon the lower part of the fixture, is exposed to a second annealing process in a temperature range between 380°C and 430°C, a transverse magnetic field sufficiently strong to develop a domain structure with a high coupling factor being applied in a manner known per se during the annealing process.

Inventors: CLARK ARTHUR E, LUU THU-VAN T, TYREN CARL, WUN-FOGLE MARILYN, CLARK, ARTHUR, E., LUU, THU-VAN, T., TYREN, CARL, WUN-FOGLE, MARILYN
Applicants: CLARK ARTHUR E, LUU THU VAN T, RSO CORP, TYREN CARL, WUN FOGLE MARILYN, CLARK, ARTHUR, E., LUU, THU-VAN, T., RSO CORPORATION N.V., TYREN, CARL, WUN-FOGLE, MARILYN
Application year: 1995
Main classification: C22C45
IPC codes: C22F1, G08B13, H01F1, H01F41, H01L41