Method of Producing Sintered Magnets with Controlled Structures and Composition Distribution

Abstract

A method of making a permanent magnet includes a step of providing an alloy powder comprising at least one rare earth element. The alloy powder is shaped and then exposed to microwave radiation or a pulsed electric current to form a sintered magnet.

1 . A method of making a rare-earth magnet, the method comprising:
 providing an alloy powder comprising at least one rare earth element;   hydrogen deprecating the alloy powder;   shaping the alloy powder; and   exposing the powder to microwave radiation to form a sintered magnet.   
     
     
         2 . The method of  claim 1  wherein the alloy powder is shaped by placing the alloy powder into a mold under a magnetic field for powder magnetic alignment. 
     
     
         3 . The method of  claim 1  wherein the alloy powder is pressed during or after shaping. 
     
     
         4 . The method of  claim 1  further comprising contacting the alloy powder with a gas prior to or during exposure to the microwave radiation. 
     
     
         5 . The method of  claim 4  wherein the gas comprises a component selected from the group consisting of helium, argon, hydrogen, nitrogen, and combinations thereof. 
     
     
         6 . (canceled) 
     
     
         7 . The method of  claim 1  wherein the microwave radiation has a power output in from about 1 to about 6 kw and a frequency from about 300 MHz to about 300 GHz. 
     
     
         8 . The method of  claim 1  wherein the alloy powder includes neodymium, iron, and boron. 
     
     
         9 . The method of  claim 8  wherein the alloy powder further includes a component selected from the group consisting of dysprosium, terbium, and combinations thereof. 
     
     
         10 . The method of  claim 9  wherein the alloy powder includes dysprosium and/or terbium having a non-uniform distribution. 
     
     
         11 . The method of  claim 10  wherein the dysprosium and/or terbium coat the alloy powder. 
     
     
         12 . The method of  claim 1  wherein the alloy powder includes samarium and iron. 
     
     
         13 . The method of  claim 12  wherein the sintered magnet comprises samarium-iron-nitrogen magnetic domains. 
     
     
         14 . A method of making a neodymium-iron-boron magnet, the method comprising:
 providing an alloy powder comprising neodymium, iron, and boron;   hydrogen deprecating the alloy powder;   shaping and pressing the alloy powder; and   exposing the powder to microwave radiation to form a sintered neodymium-iron-boron magnet.   
     
     
         15 . The method of  claim 14  further comprising contacting the alloy powder with a gas prior to or during exposure to the microwave radiation. 
     
     
         16 . The method of  claim 15  wherein the gas comprises a component selected from the group consisting of helium, argon, hydrogen, nitrogen, and combinations thereof. 
     
     
         17 . The method of  claim 15  wherein the microwave radiation has a frequency from about 300 MHz to about 300 GHz a power output from about 1 to about 6 kw. 
     
     
         18 . The method of  claim 14  wherein the alloy powder further includes a component selected from the group consisting of dysprosium, terbium, and combinations thereof. 
     
     
         19 . A method of making a rare-earth magnet, the method comprising:
 providing an alloy powder comprising at least one rare earth element;   shaping the alloy powder; and   exposing the powder to pulsed electric current.   
     
     
         20 . The method of  claim 19  wherein the pulsed electric current is from about 100 to about 10,000 amps. 
     
     
         21 . The method of  claim 19  wherein the pulsed electric current has a pulsed duration from about 1 ms to about 300 ms and a pause time of 1 to about 50 ms.