Devitrification of Mechanically Alloyed Zr-Ti-Nb-Cu-Ni-Al Glassy Powders Studied by Time-Resolved X-ray Diffraction

摘要

The crystallization of mechanically alloyed Zr₆₇Ti_6.14Nb_1.92Cu_10.67Ni_8.52Al_5.75 glassy powder is investigated by time-resolved X-ray diffraction. The powder displays a multi-step crystallization behavior characterized by the formation of a metastable nanoscale quasicrystalline phase during the first stage of the crystallization process. At higher temperatures, coinciding with the second crystallization event, the amorphous-to-quasicrystalline transformation is followed by the precipitation of the tetragonal Zr₂Cu phase (space group I4/mmm) and the tetragonal Zr₂Ni phase (space group I4 /mcm). The transformations are gradual and the quasicrystals and the subsequent phases coexist over a temperature interval of about 25K.