| Transformations in rapidly quenched ribbons Fe91-xMo8Cu1Bx for x=12-20 were investigated by diverse methods of kinetic and structure analysis. The importance of Cu as nanocrystal former was shown on the case of Fe80Mo8B12. It was shown that a change of mechanism from a two-stage process to a single stage transformation takes place with increasing boron content. The crystallization products were identified as bcc-Fe(Mo) with the degree of supersaturation decreasing with increasing boron content, B2Mo2Fe, Fe23B6 and small amounts of Fe3B. Special effects related to the appearance of crystalline phases at the surface layers of as-quenched ribbons were observed which contradict the usual pattern of surface crystallinity formation due to insufficient quenching rates or glass forming ability. These effects were correlated with changes of alloy composition and with addition of another element. Possible micromechanisms leading to this behavior were discussed in terms of quenched-in cluster structure. |
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