Introduction Ferromagnetic iron based alloys can be produced by both rapid quenching (RQ) and mechanical alloying (MA). Fe–Ni based amorphous alloys produced by rapid solidification techniques have excellent soft mag- netic properties. The magnetic properties of mechani- cally attrited materials are inferior [1, 2] to rapidly quenched materials and contamination from the milling tools may be a serious problem. Nevertheless, ribbons not attain a more significant level of applicability be- cause their form limits their technological use [3, 4]. During last decades, several papers were dedi- cated to the thermal stability analysis of powdered al- loys as well as quenched ribbons [5–7]. The use of thermal analysis on materials stability is well estab- lished [8, 9]. One of the main problems is related with the oxidation, especially of the powdered alloys [10, 11]. Furthermore, during annealing partial oxida- tion may be induced [12]. It is well known that oxides presence can modify drastically the thermomag- netization behavior [13]. This paper deals with the analysis of the thermal evaluation of powdered and quenched amorphous alloys and their respective time evolution, interest of the P/M industry. Experimental procedure The compositions analyzed in this work were Fe 40 Ni 40 Si 14 P 6, Fe 40 Ni 40 Si 10 P 10, Fe 40 Ni 40 Si 6 P 14, and Fe 60 Ni 20 Si 10 P 10 , labeled as A, B, C and D respectively. In MA, powders (particle size up to 25 μm) of ele- mental Fe, Ni, P and Si were loaded into hardened steel vial together with steel balls inside an argon filled glove box. The ball millings were performed in a planetary type mill (Frisch Pulverisette 7). The ball-to-powder mass ratio was 5:1 and the milling in- tensity was held at an intensity setting of 7. The final milling time for amorphous materials was 32 h. The amorphous melt-spun alloys A, B and C were pro- duced, in ribbon form, by quenching the molten alloy on the surface of a rapidly spinning (∼35 m s –1 ) cop- per wheel under Ar atmosphere. In this case, the Fe 3 P compound was used to prevent P sublimation. The thickness and width of the resulting ribbons were about 30 μm and 2.5 mm, respectively. The alloys were deposited in a glove-box during two years. The thermal stability of the metastable phases formed was tested, by studying their behavior on heating, in a differential scanning calorimeter (Mett- ler Toledo DSC30), under a pure Ar atmosphere. The thermal characterization was complemented by thermogravimetry (TG) under an argon atmosphere in a TGA851 Mettler Toledo equipment. The contami- nation was analyzed by induction coupled plasma (ICP) in a Liberty ICP–Varian equipment, by flame absorbance atomic spectroscopy (FAAS) in a Varian AA-1275 device and with the energy dispersive X-ray microanalysis (EDX) system coupled to a SEIZZ DSM960 A scanning electron microscope. 1388–6150/$20.00 Akadémiai Kiadó, Budapest, Hungary © 2005 Akadémiai Kiadó, Budapest Springer, Dordrecht, The Netherlands Journal of Thermal Analysis and Calorimetry, Vol. 80 (2005) 253–256 THERMAL BEHAVIOR OF SEVERAL Fe–Ni ALLOYS PREPARED BY MECHANICAL ALLOYING AND RAPID SOLIDIFICATION A. González, J. J. Suñol * , J. Bonastre, L. Escoda and J. Caleya GRMT, Dept. de Física, Universitat de Girona, Santaló s/n, 17071 Girona, Spain Several Fe–Ni–P–Si alloys were produced in an amorphous state by mechanical alloying and rapid solidification. Thermal behavior of the as prepared alloys was analyzed and compared with identical alloys stored during 1 and 2 years. During annealing time, several exothermic processes related to the structural relaxation were detected at low temperature and with further crystallization at high tem- perature. As increasing the storage time, the powdered samples were relaxed at lower temperatures. The activation energy, E, of the main crystallization process varies between 2.7 and 4.7 eV at. –1 . The E values obtained remains similar with the storage time. Small contamination from the milling tools was found. Furthermore, powdered alloys are more sensible to oxidation pro- cesses than as quenched ribbons. Keywords: Fe–Ni based alloys, mechanical alloying, melt spinning, thermal stability * Author for correspondence: joanjosep.sunyol@udg.es