Method of improving toughness of sintered RE-Fe-B-type, rare earth permanent magnets
AssigneesElectron Energy Corporation, University of Dayton
InventorsShiqiang Liu, Jinfang Liu
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Abstract
Disclosed are methods for producing compositionally modified sintered RE—Fe—B-based rare earth permanent magnets, by the addition of small amounts of Nd, Cu, Ti, Nb, or other transition metals, and mixtures thereof, to maximize fracture toughness with corresponding improved machinability, while maintaining maximum energy product, said method comprising the steps of: (a) prepare a magnetic composition; (b) melt the composition and form powders with an average particle size smaller than 5 microns from the same; (c) press the powder under a magnetic field to obtain green compacts, which are then sintered at from about 1030° C. to 1130° C., and heat treating the sintered material at from about 570° C. to 900° C.
Claims17
A method of improving the room temperature toughness of sintered RE—Fe—B-type permanent magnets comprising the step of modifying the magnet compositions by adding elements selected from the group consisting of Nb, Cu, Ti, and Nd to the composition before alloying.
A method of improving the fracture toughness of sintered RE—Fe—B-type rare earth permanent magnets comprising varying the Nd content in the magnet composition prior to powder metallurgy processing.
A method of improving the fracture toughness of sintered RE—Fe—B-type rare earth permanent magnets comprising varying the Nd content in the magnet composition prior to powder metallurgy processing.
A method of improving the fracture toughness of sintered RE—Fe—B-type rare earth permanent magnets comprising varying the Nb content in the magnet composition prior to powder metallurgy processing.
A method of improving the fracture toughness of sintered RE—Fe—B-type rare earth permanent magnets comprising varying the Cu content in the magnet composition prior to powder metallurgy processing.
A method of imparting improved fracture toughness to a class of sintered rare earth permanent magnets comprising modifying the composition of an RE—Fe—B-type permanent magnet to produce a formula selected from the group consisting of:
- (a) NdwFe94-wB6, wherein:
- w has a value between about 17 and about 22;
- (b) Nd16Fe78-xTixB6, wherein:
- x has a value between about 0.78 and about 2.34;
- (c) Nd16Fe78-yNbyB6, wherein:
- y has a value between about 1.56 and about 2.34;
- and
- (d) Nd16Fe78-zCuzB6, wherein:
- z has a value between about 0.78 and about 1.56;
- wherein said rare earth permanent magnet maintains high energy product of at least about 30MGOe, while showing an improved fracture toughness over conventional sintered Nd—Fe—B rare earth permanent magnets from between about 6% and about 74%.
A method of improving machinability of sintered rare earth permanent magnets represented by the general formula, Fe—Fe—B, while maintaining maximum energy product, and improving fracture toughness from between about 6 and 74%;
- comprising modifying the composition of said magnet, by the addition of substances selected from the group consisting of Nd, Ti, Nb, Cu and mixtures thereof, wherein said addition yields a magnet having a formulation selected from the group consisting of:
- (a) NdwFe94-wB6, wherein:
- w has a value between about 14 and about 25;
- (b) Nd16Fe78-xTixB6, wherein:
- x has a value between about 0.02 and about 3.00;
- (c) Nd16Fe78-yNbyB6, wherein:
- y has a value between about 0.02 and about 3.00;
- (d) Nd16Fe78-zCuzB6, wherein:
- z has a value between about 0.02 and about 3.00;
- and mixtures thereof.
A method for producing of rare earth permanent magnets having the formula:
- R100-xTMxAy
- with a grain size smaller than 25 microns, wherein R is one or a mixture of rare earths or yttrium, TM is one or a mixture of transition metals, A is one or a mixture of the following elements:
- Be, B, C, Mg, Al, Si, P, Ga, Ge, As, Se, In, Sn, Sb, Te, I, Pb, and Bi, and x=80-92, y=0-20;
- said method comprising the steps of:
- (a) prepare a magnetic composition;
- (b) melt the composition and form a powder with an average particle size smaller than 5 microns;
- (c) press the powder under a magnetic field to obtain green compacts, which are then sintered at from about 1030° C. to 1130° C. and thereafter heat treated at from about 570° C. to 900° C.
A method for producing rare earth permanent magnets that are consisted of a main phase and one or more minor phases. The composition of the main phase is expressed as:
- R100-mTMmAn,
- where R is one or a mixture of rare earths or yttrium, TM is one or a mixture of transition metals, A is one or a mixture of the following elements:
- Be, B, C, Mg, Al, Si, P, Ga, Ge, As, Se, In, Sn, Sb, Te, I, Pb, and Bi, and m=75-90, n=0-20;
- and
- the minor phase or phases are rich in transition metal(s) and their composition is expressed as:
- R100-fTMfAv,
- where R is one or a mixture of rare earths or yttrium, TM is one or a mixture of transition metals, A is one or a mixture of the following elements:
- Be, B, C, Mg, Al, Si, P, Ga, Ge, As, Se, In, Sn, Sb, Te, I, Pb, and Bi, and f=85-100, v=0-20;
- the total atomic percentage of transition metals, TM, in the minor soft phases is more than 85%;
- said method comprising the steps of:
- (a) prepare a magnetic composition;
- (b) melt the composition to prepare ingots, which are then crushed and milled to powders with an average particle size smaller than 5 microns;
- (c) press the powder under a magnetic field to obtain green compacts, which are then sintered at from about 1030° C. to 1130° C., followed by post-sintering heat treatment at from about 570° C. to 900° C.
A method of producing rare earth permanent magnets that possess improved fracture toughness from a compositional change selected from the group consisting of:
- (1) the presence of one or more minor phases;
- (2) the refinement of grain size;
- (3) a combination of both (a) and (b);
- said method comprising the steps of:
- (a) prepare a magnetic composition;
- (b) melt the composition, cool the molten composition and form a powder with an average particle size smaller than 5 microns;
- (c) press the powder a magnetic field to obtain green compacts, sinter the green compacts at a temperature of from about 1030° C. to 1130° C., followed by heat treat of the sintered material at a temperature of from about 570° C. to 900° C.
A method of producing rare earth permanent magnets that possess fracture toughness equal to or above 15 ft-lbs/in2 at room temperature (20° C.), said method comprising the steps of:
- (a) prepare a base magnetic composition;
- (b) melt the magnetic composition to form ingots, cool and crush the ingots and mill the crushed ingots into powders with an average particle size smaller than 5 microns;
- (c) pressed the powder under a magnetic field to obtain green compacts, and sinter the green compacts at temperature of from about 1030° C. to 1130° C., followed by heat treatment of the sintered material at from about 570° C. to 900° C.
Dependencies are inferred from the claim text.