Bulk ferromagnetic glasses in the Fe-Ni-P-B system

The ferromagnetic metallic glass Fe40Ni40P14B6. available only as 30-50 mum thick ribbons, has been extensively studied over the last three decades. W e used a flux-melting and water-quenching technique to prepare bulk glassy Fe40Ni40P14B6 alloys in the form of 2-mm diameter spheres and 1-mm diameter rods. The Curie temperature for the bulk glasses is higher than the averag e value of Curie temperatures reported for the rapidly quenched ribbons. Th e glass-transition temperature and the crystallization temperature of the b ulk glasses are lower and higher, respectively. than the average values rep orted for rapidly quenched ribbons, making the supercooled-liquid region as wide as 42 K. The bulk glasses crystallize by a homogeneous nucleation fol lowed by a growth at a constant rate. The nucleation rate in the bulk glass es is four orders of magnitude lower than in the rapidly quenched ribbons, suggesting that the previous thickness limitation was due to impurities in the melt (heterogeneous nucleation). Published by Elsevier Science Ltd. on behalf of Acta Materialia Inc.