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

The ferromagnetic metallic glass Fe₄₀Ni₄₀P₁₄B₆, available only as 30-50 μm thick ribbons, has been extensively studied over the last three decades. We 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 average value of Curie temperatures reported for the rapidly quenched ribbons. The glass-transition temperature and the crystallization temperature of the bulk glasses are lower and higher, respectively, than the average values reported for rapidly quenched ribbons, making the supercooled-liquid region as wide as 42 K. The bulk glasses crystallize by a homogeneous nucleation followed by a growth at a constant rate. The nucleation rate in the bulk glasses 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 Metallurgica Inc.