Regensburg 2007 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 9: Liquid and amorphous materials III

MM 9.3: Vortrag

Montag, 26. März 2007, 15:15–15:30, H4

Primary crystallization reaction in Al-Y-Fe glasses containing low melting point nanoparticles — •Nancy Boucharat¹, Harald Rösner², and Gerhard Wilde¹ — ¹Institut für Materialphysik, Universität Münster, Wilhelm-Klemm-Strasse 10, 48149 Münster, Germany — ²Institut für Nanotechnologie, Forschungszentrum Karlsruhe, P.O.B. 3640, 76021 Karlsruhe, Germany

Many rapidly quenched Al-rich alloys partially devitrify via a primary crystallization reaction, which results in the development of a high num-ber density of homogeneously dispersed Al-nanocrystals. Although sev-eral experimental results are consistent with the formation of nucleation sites during rapid quenching via homophase catalysis, the nature and the origin of the nucleation sites is not yet completely resolved. To assess the role of the as-quenched state in the nanocrystallization process, 1at.% Pb or 1at.% In, respectively were substituted for Al in an Al-Y-Fe glass prior to rapid quenching. The microstructure of the respective products consists of a homogeneous dispersion of nanocrystalline Pb particles or In-enriched regions within an amorphous Al-Y-Fe matrix. In both cases, the primary crystallization is strongly shifted to lower temperatures compared to the reaction in the inclusion-free sample. While likely mechanisms have been proposed to explain the catalytic effect of Pb inclusions on the nanocrystallization process, the analyses on the In-containing sample give new evidence that the inclusions generate a modification of the local structural arrangement of the amorphous matrix promoting the retention of quenched-in nuclei during the quenching process.