International Scholarly Research Network ISRN Metallurgy Volume 2012, Article ID 602108, 5 pages doi:10.5402/2012/602108 Research Article Study of Amorphous-Crystalline Phase Transformations by DSC and Dilatometer in the Case of Al-Based Amorphous Alloys ´ Eva Fazakas, 1 B´ ela Varga, 2 and Lajos K ´ aroly Varga 1 1 Wigner Research Centre for Physics, Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, Budapest 1525, Hungary 2 Faculty of Materials Science and Engineering, Transylvania University, Bulevardul Eroilor, No. 29, 500036 Brasov, Romania Correspondence should be addressed to ´ Eva Fazakas, efazakas@szfki.hu Received 21 August 2012; Accepted 11 September 2012 Academic Editors: R. Hebert and A. Tuissi Copyright © 2012 ´ Eva Fazakas et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The amorphous-crystalline transformation is studied by DSC and dilatometer. From the DSC signal the characteristic temperatures and the heat evolved during each transformation step can be determined. The dilatometer depicts the thermal contractions accompanying the changes in topological short range order. Although the characteristics temperatures determined by DSC and dilatometer, two methods are slightly different their dependences on the heating rate are very similar, where from the activation energies of each transformation steps can be determined using the Kissinger plots. As an example, two aluminum-based amorphous ribbon samples (Al 88 Mm 5 Ni 5 Co 2 and Al 85 Y 8 Ni 5 Co 2 ) will be measured and compared. 1. Introduction 20 years have been passed since the discovery of the first ductile Al-based amorphous alloy ribbons with superior mechanical properties compared to the conventional alu- minum alloys [1, 2]. These ribbons have been obtained by melt spinning technique starting from a multicomponent ingot contained as a rule rare earth (RE) metal and one or two late transition metals (TMs) [3]. It has been found that alloys with high glass forming ability (low critical cooling rate for glass formation or large critical thickness) are the so- called strong metallic glasses in the Angell plot [4]. Unfor- tunately, the Al-based glasses belong to the fragile glasses with low glass forming ability and consequently no bulk metallic glass (BMG) exits on Al-base. The bulk amorphous samples can be obtained only by hot consolidation of the amorphous ribbon flakes, which should be performed below the transformation temperature. Therefore, the thermal stability of these ribbons (in amorphous or nanocrystalline state) marks a limit of their applicability, and the study of the kinetics of crystallization of Al-based alloys is an important task to which several studies have been devoted so far (for a review, see [5]). In order to reduce the price of the alloy in this paper we have studied a composition containing Mischmetal instead of pure RE element. Mischmetal (Mm) is a natural mixture of rare earth metals; typical composition contains 48% cerium, 25% lanthanum, 17% neodymium, and 5% praseodymium, with the balance being the other lanthanides. Many studies were devoted to compare the behavior of Mm-substituted alloys with those with pure rare earth elements [5–7]. In the present paper the kinetics of crystallization are studied for two alloys of nominal compositions Al 85 Y 8 Ni 5 Co 2 and Al 88 Mm 5 Ni 5 Co 2 by DSC and dilatometer. We have chosen these two compositions because they show big differences during dilatometer investigations although both show three transformation steps in their DSC patterns. The dilatome- ter is sensitive to the volume changes accompanying the amorphous-crystalline transformation, that is, to the change in topological short range order (TSRO). In contrast with dilatometer, the DSC is sensitive to the heat evolved during the formation of new phases, that is, to the changes in