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M: Metallphysik

M 9: Flüssige und amorphe Metalle III

M 9.3: Vortrag

Montag, 8. März 2004, 17:00–17:15, H16

Crystallization Behavior of Zr-Ti-Ni-Cu-Be type glasses — •s. Mechler, N. Wanderka, and M.-P. Macht — Hahn-Meitner-Institut Berlin, Glienicker Strasse 100, 14109 Berlin

The Zr-Ti-Ni-Cu-Be bulk metallic glasses belong to the best glassformers and most stable glasses. However, the stability of the individual glasses of this family depends on their composition. Accordingly their crystallization behavior differs with composition and temperature . To investigate these dependencies the crystallization behavior of Zr₄₁Ti₁₄Ni₁₀Cu_12.5Be_22.5 (V1), Zr_46.8Ti_8.2Ni₁₀Cu_7.5Be_27.5 (V4) and Zr₅₀Ti₅Ni₁₀Cu₁₀Be₂₅ (V12) is studied by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Samples of the glasses were annealed isothermally at 643 K, as well as after constant heating in the DSC with a rate of 4K/min. The phase characterization from the XRD patterns is performed by use of a Rietveld–Refining Procedure. During isothermal annealing icosahedral quasicrystals form in V1 and V4. The quasicrystals are depleted of Be and enriched in Ti. Mainly one crystalline phase, but no quasicrystals, crystallizes in V12. After constant heating of the glasses up to higher temperatures in the DSC only in V1 the first phase was quasicrystalline. During further heating, these quasicrystals transform into a Laves phase, whereas the remaining amorphous phase crystallizes into several phases, like Be₂Zr. During constant heating of the V4 and V12 glass mainly a tetragonal phase crystallizes.The lattice constants of this tetragonal phase alter systematically with increasing temperature. Simultaneously to this alterations intermetallic phases appear in the microstructure.