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M: Metallphysik
M 9: Amorphe und metastabile Metalle
M 9.6: Vortrag
Dienstag, 28. März 2000, 16:30–16:45, H6
Pressure Effect on Crystallization Kinetics in Amorphous Solids — •F. Ye1,2,3, K. Lu1, R. Würschum2, and H.-E. Schaefer3 — 1State Key Laboratory for RSA, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, People’s Republic of China — 2Forschunggszenntrum Karlsruhe, Institut für Nanotechnologie, D-76021 Karlsruhe, Germany — 3Institut für Theoretische und Angewandte Physik, Universität Stuttgart, D-70550 Stuttgart, Germany
In many amorphous alloys, it was found that an external pressure suppresses the crystallization process. An interpretation for the enhanced thermal stability of the amorphous solids under pressure is that the applied pressure impedes the atomic diffusion during the crystallization process. To verify this consideration, we investigated the pressure effect on two types of crystallization process: polymorphous (a-Se) and primary (Al89La6Ni5) crystallization. It was found that although no long-range atomic diffusion occurs in the polymorphous crystallization, the applied pressure suppresses the crystallization of amorphous Se. The crystallization temperature is increased by 49 K/GPa. For the crystallization of the amorphous Al89La6Ni5 alloy, the precipitation temperature of fcc-Al decreases from 495 to 440 K, when the applied pressure increases from ambient pressure to 0.9 GPa. Meanwhile, the thermal stability of the residual amorphous phase with Al dispersions is elevated at higher pressures. A model was developed to describe the nucleation process under pressure, which affects the nucleation barrier and the critical nucleus diameter according to the volume change involved in the nucleus formation.