Berlin 2008 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 27: Liquid and Amorphous Metals II
MM 27.5: Talk
Wednesday, February 27, 2008, 16:45–17:00, H 0107
Strain- and Temperature-induced Glass-to-Crystal Transformations in Al-Ni-La Glass — •Jens Vierke1, Gerhard Schumacher1, Ingwer A. Denks1, Nelia Wanderka1, Markus Wollgarten1, John Banhart1, Ivo Zizak2, Vitaly P. Pilyugin3, Martin Balog4, Juray Nagy4, and František Simančik4 — 1Hahn-Meitner-Institute Berlin, Germany — 2BESSY Berlin, Germany — 3Ural Branch of the Russian Academy of Sciences, Yekaterinburg, Russia — 4Slovak Academy of Sciences, Bratislava, Slovakia
Helium-atomized amorphous Al85Ni10La5 powders were consolidated using uni-axial pressing, equal channel angular pressing (ECAP) and high pressure torsion (HPT) at temperatures ranging from room temperature to 400°C. The samples were investigated by scanning electron microscopy (SEM), in-situ angle-dispersive (AD) and ex-situ energy-dispersive (ED) X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). As-atomized powders show a glass transition and a subsequent simultaneous crystallization of fcc-Al and intermetallic phases upon continuous and isothermal heating. Samples consolidated below the crystallization temperature show only fcc-Al nanocrystals and a residual amorphous phase. They exhibit no glass transition upon continuous heating. The amount of fcc-Al nanocrystals increases with strain and processing temperature as revealed by ED XRD measurements along the disc radius of a HPT-sample and by AD XRD along the pressing direction of ECAP-samples stopped halfway in the ECAP-die. The results indicate that the primary precipitation of fcc-Al is strain-induced and possibly athermal.