Glass-forming ability and I-phase formation in Y-doped Zr-Nb-Cu-Ni-Al glassy alloys

摘要

The effect of yttrium addition on the Glass-Forming Ability (GFA) and thermal stability of Zr_(58)Nb_3Cu_(16)Ni_(13)Al_(10) alloy has been investigated. (Zr_(0.58)Nb_(0.03)Cu_(0.16)6Ni_(0.13)Al_(0.10))_(100-x)Y_x (x = 0-3 at. percent) metallic glasses were formed by melt-spinning and copper-mould casting methods. By adding 1.5 at. percent Y, the GFA of Zr_(58)Nb_3Cu_(16)Ni_(13)Al_(10) alloy is dramatically enhanced, and the critical diameter for glass formation increased from 7 mm to as large as 15 mm. The crystallization processes of the Y-free and Y-doped glassy alloys were studied by differential scanning calorimetry, X-ray diffraction and transmission electron microscopy. It was found that the initial precipitates are face-centred-cubic Zr_2Ni and tetragonal Zr_2Ni phases for the Y-free Zr_(58)Nb_3Cu_(16)Ni_(13)Al_(10) alloy, but a single icosahedral quasi-crystalline phase for the Y-doped (Zr_(0.58)Nb_(0.03)Cu_(0.16)6Ni_(0.13)Al_(0.10))_(98.5)Y_(1.5) alloy. This suggests that the yttrium greatly affects the local atomic configuration, which may be the origin for the enhanced GFA of the Y-doped alloys.