Abstract A process for preparing novel sintered cobalt-rare earth intermetallic products which can be magnetized to form permanent magnets having stable improved magnetic properties. A particulate mixture is formed of a base CoR alloy and an additive CoR alloy, where R is a rare earth metal. The base CoR alloy is one which, at sintering temperature, exists as a solid Co5R intermetallic single phase. The additive CoR alloy is richer in rare earth metal than the base CoR alloy, and at sintering temperature is at least partly liquid. The base and additive alloys, in particulate form, are each used in an amount to form a mixture which has a cobalt and rare earth metal content substantially corresponding to that of the final desired sintered product. The mixture is pressed into compacts and sintered to the desired sintered product phase composition and density. At sintering temperature, the final sintered product has a phase composition lying outside the Co5R single phase on the rare earth richer side. Specifically, the final sintered product contains a major amount of the Co5R solid intermetallic phase and up to about 35 percent by weight of the product of a second solid CoR intermetallic phase which is richer in rare earth content than the Co5R phase.
A SINTERED PRODUCT HAVING SIGNIFICANTLY ENCHANCED PERMANENT MAGNET PROPERTIES WHICH ARE SUBSTANTIALLY STABLE IN AIR AT ROOM TEMPERATURE CONSISTING ESSENTIALLY OF COMPACTED PARTICULATE COBALT-RARE EARTH ALLOY CONSISTING ESSENTIALLY OF A CO5R INTERMETALLIC PHASE AND A COR INTERMETALLIC PHASE WHICH IS RICHER IN RARE EARTH METAL CONTENT THAN SAID CO5R PHASE, SAID CO5R INTERMETALLIC PHASE BEING PRESENT IN AN AMOUNT OF AT LEAST 65% BY WEIGHT OF SAID SINTERED PRODUCT AND SAID COR INTERMETALLIC PHASE WHICH IS RICHER IN RARE EARTH METAL CONTENT THAN SAID CO5R PHASE BEING PRESENT IN A POSITIVE AMOUNT HAVING A VALUE RANGING UP TO 35% BY WEIGHT OF SAID PRODUCT WHERE R IS A RARE EARTH METAL OR METALS, SAID SINTERED PRODUCT HAVING A DENSITY OF AT LEAST 87 PERCENT OF THEORETICAL AND HAVING PORES WHICH ARE SUBSTANTIALLY NON-INTERCONNECTING AND WHEREIN THE COMPONENT GRAINS HAVE AN AVERAGE SIZE LESS THAN PS 30 MICRONS, SAID SINTERED PRODUCT BEING PRODUCED BY ADMIXING PARTICLES OF A BASE COBALT-RARE EARTH METAL ALLOY AND AN ADDITIVE COBALT-RARE EARTH METAL ALLOY, SAID PARTICLES HAVING AN AVERAGE SIZE RANGING TO ABOUT 10 MICRONS, SAID BASE ALLOY EXISTING AT SINTERING TEMPERATURE AS A SOLID CO5R INTERMETALLIC PHASE AND SAID ADDITIVE ALLOY EXISTING AT SINTERING TEMPERATURE AS AT LEAST A PARTLY PHASE AND BEING RICHER IN RARE EARTH METAL CONTENT THAN SAID BASE ALLOY, SAID BASE ALLOY AND SAID ADDITIVE ALLOY EACH BEING USED TO FORM A MIXTURE WHICH HAS A COBALT AND RARE EARTH METAL CONTENT SUBSTANTIALLY CORRESPONDING TO THAT OF THE FINAL SINSTERED PRODUCT WITH SAID ADDITIVE ALLOY BEING PRESENT IN AN AMOUNT OF AT LEAST 0.5 PERCENT BY WEIGHT OF SAID MIXTURE, PRESSING AND MIXING INTO A GREEN BODY, AND SINSTERING SAID GREEN BODY IN A SUBSTANTIALLY INERT ATMOSPHERE TO PRODUCE SAID SINSTERED PRODUCT.
Claim 2
Dependent Claim
292 words
A SINTERED PRODUCT HAVING SIGNIFICANTLY ENCHANCED PERMANENT MAGNET PROPERTIES WHICH ARE SUBSTANTIALLY STABLE IN AIR AT ROOM TEMPERATURE CONSISTING ESSENTIALLY OF COMPACTED PARTICULATE COBALT-RARE EARTH ALLOY CONSISTING ESSENTIALLY OF A CO5R INTERMETALLIC PHASE AND A COR INTERMETALLIC PHASE WHICH IS RICHER IN RARE EARTH METAL CONTENT THAN SAID CO5R PHASE, SAID CO5R INTERMETALLIC PHASE BEING PRESENT IN AN AMOUNT OF AT LEAST 65% BY WEIGHT OF SAID SINTERED PRODUCT AND SAID COR INTERMETALLIC PHASE WHICH IS RICHER IN RARE EARTH METAL CONTENT THAN SAID CO5R PHASE BEING PRESENT IN A POSITIVE AMOUNT HAVING A VALUE RANGING UP TO 35% BY WEIGHT OF SAID PRODUCT WHERE R IS A RARE EARTH METAL OR METALS, SAID SINTERED PRODUCT HAVING A DENSITY OF AT LEAST 87 PERCENT OF THEORETICAL AND HAVING PORES WHICH ARE SUBSTANTIALLY NON-INTERCONNECTING AND WHEREIN THE COMPONENT GRAINS HAVE AN AVERAGE SIZE LESS THAN PS 30 MICRONS, SAID SINTERED PRODUCT BEING PRODUCED BY ADMIXING PARTICLES OF A BASE COBALT-RARE EARTH METAL ALLOY AND AN ADDITIVE COBALT-RARE EARTH METAL ALLOY, SAID PARTICLES HAVING AN AVERAGE SIZE RANGING TO ABOUT 10 MICRONS, SAID BASE ALLOY EXISTING AT SINTERING TEMPERATURE AS A SOLID CO5R INTERMETALLIC PHASE AND SAID ADDITIVE ALLOY EXISTING AT SINTERING TEMPERATURE AS AT LEAST A PARTLY PHASE AND BEING RICHER IN RARE EARTH METAL CONTENT THAN SAID BASE ALLOY, SAID BASE ALLOY AND SAID ADDITIVE ALLOY EACH BEING USED TO FORM A MIXTURE WHICH HAS A COBALT AND RARE EARTH METAL CONTENT SUBSTANTIALLY CORRESPONDING TO THAT OF THE FINAL SINSTERED PRODUCT WITH SAID ADDITIVE ALLOY BEING PRESENT IN AN AMOUNT OF AT LEAST 0.5 PERCENT BY WEIGHT OF SAID MIXTURE, PRESSING AND MIXING INTO A GREEN BODY, AND SINSTERING SAID GREEN BODY IN A SUBSTANTIALLY INERT ATMOSPHERE TO PRODUCE SAID SINSTERED PRODUCT.