Effect of microstructure on the magnetic properties of mold-cast and melt-spun Nd-Fe-Co-Al amorphous alloys

In this paper, we discuss the role of quenched-in crystallites and amorphous matrix for the large coercivity of Nd-Fe-Co-Al bulk cylinders. The present investigations of mold-cast and melt-spun Nd60FexCo30-Al-10 (0 less than or equal to x less than or equal to10) samples show that the Fe-rich as-cast (x = 7.5, 10) bulk cylinders exhibit a partially crystalline structure, whereas the meltspun ribbons and Co-rich as-cast (x less than or equal to 55) bulk cylinders are amorphous. Spheruite-like regions consisting of Nd-rich and metastable (approximate toNd(36),Fe31Co28,Al-4) crystallites along with an amorphous matrix were observed in the as-cast Fe-rich bulk cylinders. The Co-rich ribbons and bulk cylinders with x less than or equal to 5 show a distinct endothermic peak in the DSC traces due to a glass transition in the range of 477-489 K. With further increasing Fe content the glass transition is masked by the crystallization. The effect of the Fe/Co ratio on the magnetic properties and the glass transition is discussed. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.