Dynamic mechanical analysis of copper-containing magnetic Pr-Fe-B alloys

The mechanical properties of magnetic alloys with compositions Pr17Fe76.5B5Cu1.5 and Pr17Fe73.5B8Cu1.5 were studied with the aid of a dynamic mechanical analyzer. The elastic modulus of the annealed Pr17Fe76.5B5Cu1.5 alloy varied substantially (∼24%) and irreversibly when it was heated to 450 °C and cooled to room temperature. Conversely, the elastic modulus of the annealed Pr17Fe73.5B8Cu1.5 alloy varied only slightly upon heating to 450 °C and cooling to room temperature. This behavior has been attributed to the precipitation of excess rare earth from the lattice of the matrix phase and to the Pr6Fe13Cu and Pr1+εFe4B4 phases.