TEMPERATURE COMPENSATION OF BONDED RARE-EARTH MAGNETS BY BLENDING OF ALLOY POWDERS.

THIS PROJECT WILL TRY TO DEMONSTRATE A METHOD OF INTERNAL TEMPERATURE COMPENSATION FOR BONDED RARE-EARTH PERMANENT MAGNETS, PARTICULARLY FOR THOSE BASED ON ND-FE-B. THE STRONG TEMPERATURE DEPENDENCE OF THE SPONTANEOUS MAGNETIZATION (M) OF THE LATTER IN THE TYPICAL USE RANGE, O C TO +150 C, IS A PROBLEM IN MANY APPLICATIONS. (MS DROPS QUICKLY AS T INCREASES.) THIS CANNOT BE REMEDIED BY ALLOYING A HEAVY RARE EARTH INTO THE BASIC MAGNETIC PHASE AS IN SINTERED SM-CO-BASED MAGNETS. OUR APPROACH IS TO BLEND COARSE POWDERS OF THE MAIN MAGNETICCONSTITUENT (ND-FE-B OR SM-CO) AND A SECOND HARDMAGNETIC ALLOY THAT HAS A HIGH POSITIVE TEMPERATURE COEFFICIENT (TC) OF MS, THUS LESSENING THE VARIATION OF M WITH T FOR THE COMPOSITE, OR IN THE EXTREME MAKING MS NEARLY CONSTANT. THIS WOULD PERMIT CREATING A WHOLE FAMILY OF BONDED MAGNETS HAVING A RANGE OF TCS FROM ONLY 2 OR 3 MAGNETIC MASTER ALLOYS. THE METHOD IS EQUALLY APPLICABLE TO MATRIX MAGNETS WITH ANY KIND OF BINDER, POLYMERIC, METALLIC, OR OTHER. IT CAN ALSO BE USED TO COMPENSATE SM-CO-BASED MATRIX MAGNETS. IN PHASE I WE WOULD IDENTIFY SUITABLE COMPONENT ALLOY COMPOSITIONS (WHICH MUST BE AVAILABLE IN PRESINTERED FORM WITH HIGH COERCIVITY), ANALYZE THE PM PROPERTIES AND M VS. TOBTAINABLE FROM DIFFERENT BLENDS, AND DEVISE A MATHEMATICAL MODEL FOR "ENGINEERING" THE TEMPERATURE COEFFICIENT. WE WOULD PREPARE A COMPENSATION ALLOY, LEARN EXPERIMENTALLY HOWTO HARDEN IT, PREPARE SOME BONDED MAGNETS FROM POWDER BLENDSAND MEASURE THE TEMPERATURE DEPENDENCE OF THEIR PM PROPERTIES TO PROVE FEASIBILITY OF THE CONCEPT AND VERIFY THE MATHEMATICAL MODEL.