Processing and Characterization of Rare Earth Transition Metal Powders Produced by Reduction Diffusion Process

Abstract

Rare earth-transition metal intermetallics, especially those containing the abundant light rare earth elements, have established themselves as the most important materials for high performance permanent magnets. The important permanent magnetic newlineproperties, such as coercivity, remanence and temperature stability are influenced by the microstructure and phase chemistry. The processing route used to fabricate the permanent magnet has a bearing on the said properties and is critical in determining the final magnetic performance. The rare earth permanent magnets are commercially produced either by conventional powder metallurgy route or by rapid quenching newlinefollowed by hot-pressing and die-upsetting. A few other techniques, tried at a smaller scale, include mechanical alloying, melt spraying and liquid dynamic compaction and extrusion. The powder metallurgy route has, however, taken precedence over other manufacturing processes as it has yielded the optimum microstructure resulting in translation of the intrinsic properties of a rare earth-transition metal compound into the characteristic parameters of a permanent magnet in the best possible manner. The demand for various rare earth permanent magnet materials for applications in the aerospace, defence, electronics and automotive industries continues to grow as the need for smaller, more powerful and light weight magnets prominently figures in the newlinelist of materials available to design engineers. newlineThe rare earth permanent magnets, abbreviated as REPM, are metal magnets consisting of alloys of one or more of 3d-transition metals, e.g. Fe and Co, with the newlineelements of the rare earth group. In these materials, the transition metals provide for a high saturation magnetization, whereas the rare earth elements contribute largely towards the high magnetocrystalline anisotropy, which is innate to the high coercivity. newline newline