Processing of Neodymium-Iron-Boron melt-spun ribbons to fully dense magnets

Over-quenched melt-spun ribbons of nominal composition Nd0.14(Fe0.91B0.09)0.86can be compacted to fully dense permanent magnets by hot-pressing at 700-750°C to 100 kPa (-15 kpsi). The resulting material is only slightly magnetically aligned with room temperature magnetics: kG/19 kOe. Die-upsetting to a thickness reduction of 50% produces kG/12 kOe and is accompanied by a lateral plastic flow of the ribbons and a corresponding ribbon thickness reduction. The alignment arises from anisotropic grain growth and grain rotation which produces platelet shaped grains oriented perpendicular to the press direction. The temperature dependence of Brfor both hot-pressed (MQ2) and die-upset (MQ3) ribbons corresponds to a temperature coefficient of -0.25%/°C. The Hcitemperature coefficients are -0.35%/°C and -0.45%/°C, respectively. High temperature aging in air produces negligible loss.