Dresden 2003 – scientific programme

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M: Metallphysik

M 39: Flüssige und amorphe Metalle IV

M 39.2: Talk

Thursday, March 27, 2003, 12:00–12:15, IFW D

Crystallization Behaviour of Mechanically Alloyed Zr-Cu-Al-Ni Glass Composites Containing Second-Phase ZrC Particles — •Stefano Deledda, Jürgen Eckert, and Ludwig Schultz — IFW Dresden, Institute of Metallic Materials, P.O. Box 270016, 01171 Dresden

Glassy Zr₅₅Cu₃₀Al₁₀Ni₅ composite powders containing up to 30 vol.% of nanometer-size ZrC particles were prepared by mechanical alloying. Isothermal differential scanning calorimetry was carried out and the Johnson-Mehl-Avrami model was applied to investigate the crystallization behaviour for increasing ZrC volume fractions. An overall slow down of the crystallization was observed and changes in the Avrami exponent from n = 4 to n = 3 imply that the nucleation rate approaches zero after the early stages of crystallization. It is suggested that, for large ZrC volume fraction, carbide particles/glassy matrix interfaces may promote nucleation of crystalline phases. Comparison with results for single-phase mechanically alloyed Zr-Cu-Al-Ni-C glassy powders also point out a contribution from carbon atoms present in the glassy phase, as slight deviations from the starting composition of the glassy matrix result from non-negligible ZrC-dissolution processes during mechanical alloying.