EVOLUTION OF FREE VOLUME IN ANNEALED Fe-Mo-Cu-B-TYPE ALLOY STUDIED BY POSITRON ANNIHILATION

Milan Pavúk –Marcel Miglierini

   Positron annihilation lifetime spectroscopy (PALS) has been applied to study the microstructural changes in NANOPERM-type metallic Fe₇₆Mo₈Cu₁B₁₅ alloy after heat treatment. Samples in as-quenched state were isothermally annealed at five chosen temperatures in the range between 330 and 700 °C for 1 hour annealing time. The decrease of excess free volume in the as-quenched structure upon annealing is well observed by a decrease of positron lifetime. The combination of PALS with other experimental methods (in particular magnetic measurements) have shown that minimum of free volume found in sample annealed at 550 °C coincides with the temperature at which superior magnetic properties are observed.

Keywords: PALS, positron annihilation, nanocrystalline alloys, amorphous alloys, excess free volume

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