Gm Global Technolgoy Operations, Inc.

Earl G Brewer

Robert W Lee

Carlton D Fuerst

Frederick E Pinkerton

Jan F Herbst

Tenneille Weston Capehart

Charles Bernard Murphy

John J Croat

Composite bodies of magnetostrictive materials of the type RE-Fe.sub.2, where RE is one or more of the rare earth elements, preferably samarium or terbium, can be suitably hot pressed with a matrix metal selected from the group consisting of aluminum, copper, iron, magnesium or nickel to form durable and machinable magnetostrictive composites still displaying appreciable magnetostrictive strains.

Magnetostrictive composites

In a preferred method, a magnetically hard composition is prepared by intermingling rare earth (RE) metal, transition metal (TM) and boron (B) alloy powders of the general formula RE-(Fe.sub.(1-x) Co.sub.x)-B. The value of x ranges from 0 to 1 and is different for each of the powders, thus providing a blend of alloy powders with diverse Curie temperature (T.sub.c) and a less abrupt rate of change of thermal expansion and/or specific heat with temperature, as compared to a single alloy powder. The magnetically hard compositions with improved thermomechanical properties are formed from two or more alloy powders. Preferably, two alloy powders are used and the value of x for the first alloy is less than about 0.1. The value of x for the second alloy is in a range of about 0.1 to about 0.6, and preferably 0.3 to 0.5. When the intermingled alloy powders of the invention are hot pressed with or without subsequent hot working, a magnetically hard body is formed and it is characterized by a lesser rate of change of specific heat and/or thermal expansion with temperature as compared to any one of the single alloy powders similarly hot pressed or hot worked.

Method to enhance the thermomechanical properties of hot-formed magnets

Anisotropic permanent magnets consisting essentially of RE.sub.2 TM.sub.14 C are prepared by hot working suitable iron-neodymium/praseodymium-carbon containing alloys so as to produce deformed fine grains of the above essential magnetic phase.

Hot worked rare earth-iron-carbon magnets

Diffusion alloying techniques are used to introduce low level additives into hot-worked Nd-Fe-B magnets. The powdered metal is added to the rapidly solidifed ribbons of the magnetic alloy prior to hot working. Diffusion alloying during hot-working permits the final chemistry of the magnet and more specifically the grain boundaries to be determined during the final processing steps. Elements which diffuse into the matrix, such as zinc, copper and nickel, enhance the coercivity by as much as 100 percent in die-upset magnets. At optimum levels, approximately 0.5-0.8 weight percent, the additives did not diminish the remanence or energy product of the magnet.

Alloying low-level additives into hot-worked Nd-Fe-B magnets

The coercivity of fine grain, hot worked RE.sub.2 TM.sub.14 B type permanent magnets is improved by quenching the material from a temperature greater than about 500.degree. C. to below about 100.degree. C.

Coercivity in hot worked iron-neodymium boron type permanent magnets

Magnetically isotropic, fine grain, RE.sub.2 Fe.sub.4 B phase containing particulate material is hot pressed to full density and bonded to a metal backing layer of desired shape and composition. Additionally, if desired, the fully dense isotropic material can be further deformed in a direction lateral to the press direction so as to strain the particles to align the preferred magnetic axes of the crystal grains therein and thus form a laminate of a magnetically anisotropic magnet layer bonded to a metal backing layer.

Method for producing laminated bodies comprising an RE-FE-B type

A method to produce rare earth (RE), iron, boron type anisotropic permanently magnetic material includes forming magnetically isotropic coarse powder particles of melt-spun alloy with a very fine grain RE.sub.2 FE.sub.14 B phase. The particles are mixed with inert particles of a size and of a weight percentage of the mixture to separate the powder particles for preventing hot work bonding therebetween. The mixture is hot pressed to cause the magnetically isotropic particles to be compressed in a direction parallel to the press direction so as to strain the particles to cause crystallites to be oriented along a crystallographically preferred magnetic axis resulting in particles of anisotropic permanently magnetic material.

Method for producing anisotropic RE-FE-B type magnetically aligned

A method to increase the volume fraction of magnetically aligned material in rare earth (RE), iron, boron type anisotropic permanently magnetic material includes forming an adaptively shaped fully dense substantially magnetically isotropic preform from relatively coarse powder particles of melt spun alloy with a very fine grain Re.sub.2 Fe.sub.14 B phase. The preform is heated and die upset to provide uniformity of strain in the perform as it is conformed to the die thereby to cause an increased percentage of the crystallites to be oriented along a crystallographically preferred magnetic axis which increases the energy product of a resultant magnet.

Die-upset manufacture to produce high volume fractions of RE-Fe-B type

An improved grid for computer-aided strain analysis of a deformed metal sheet comprises a preferred grid pattern of noncontacting uniform solid circles formed of thin plated copper and surrounded by exposed sheet surface. The copper circles are applied to the sheet surface and the sheet is deformed, whereupon the circles are stretched into ellipses. After sheet deformation, the ellipse pattern is oxidized to enhance contrast between the copper ellipses and the surrounding sheet metal and thereby enable the pattern to be reliably photographed for computer analysis.

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Warren, MI, United States of America

Earl G Brewer