Local Order Changes in Amorphous Zr52.5Hf2Ti7.5Cu20Al10Ni8 Alloy Upon Crystallization

L. C. DAMONTE; M. A. BAB; L. A. MENDOZA-ZELIS; S. DELEDDA; J. ECKERT

JOURNAL OF METASTABLE AND NANOCRYSTALLINE MATERIALS

Trans Tech Publications (ttp)

Año: 2004 vol. 20 p. 499 - 504

1422-6375

The local order in Zr52.5Hf2Ti7.5Cu20Al10Ni8 alloy is investigated by perturbed angular correlation (PAC) in the as-prepared state and after different crystallization steps. The initial amorphous stage was checked by differential scanning calorimetry and x-ray diffraction experiments. PAC results showed that the initial amorphous state is well described by a dense random packing of ions. After the first crystallization step (Ta=723 K) at least two two wide distributions of frequencies are observed. One of them can be associated with a Ti2Ni-type phase that may also be observed in the X-ray diffraction pattern at a trace level. Further heat treatments lead to the precipitation of different intermetallic equilibrium compounds: Zr2Cu, ZrAl2. These results in combination with DSC and X-ray determinations on the annealed alloy may help to identify the mechanisms for phase formation upon each annealing step.