A novel and simple method is proposed for investigating the complex microstructure of a Sm(Co/Fe/Cu/Zr)7.3 permanent magnet alloy. It makes use of potentiostatic etching in concentrated orthophosphoric acid at specific potentials to reveal the platelet, zonal, and/or grain boundary phases so that they can be viewed by conventional scanning electron microscopy. The whole procedure can be accomplished within a short period of time, no sophisticated techniques are involved, and bulk specimens up to several cm in diameter can be examined. Details of the etching technique are described and scanning electron micrographs are compared with transmission electron micrographs from the same specimen.
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