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 resistance without coating or surface treatment. By the addition of elements to form intermetallic phases the intergranular region of this new material consists mainly of intermetallic phases and the corrosible Nd-rich phase is avoided as far as possible. Same additives which guarantee excellent corrosion properties comparable to SmCo permanent magnets are used to get better temperature coefficients of the remanence and the coercivity. A reduction of the temperature influence by 20 to 30% is achieved. Magnetic properties can be adjusted for the operation temperatures. By variation of the chemical composition high temperature applications up to 250°C can be accommodated