NEW CORROSION-RESISTANT MATERIALS BASED ON NEODYM-IRON-BORON

The properties of Neodymium-Iron-Boron sintered magnets are optimised to attain high temperature stability and excellent corrosion resistanc e without coating or surface treatment. By the addition of elements to form intermetallic phases the intergranular region of this new materi al consists mainly of intermetallic phases and the corrosible Nd-rich phase is avoided as far as possible. Same additives which guarantee ex cellent corrosion properties comparable to SmCo permanent magnets are used to get better temperature coefficients of the remanence and the c oercivity. A reduction of the temperature influence by 20 to 30 % is a chieved. Magnetic properties can be adjusted for the operation tempera tures. By variation of the chemical composition high temperature appli cations up to 250 degrees C can be accommodated.