Compositional dependence of crystallization kinetics in Zr-Ni-Al metallic glasses

Crystallization kinetics of the Zr70-xNi14+xAl16 (x = 0, 5, 10, 15, and 20 at.%) metallic glasses (MGs) was investigated using the non-isothermal and isothermal methods, respectively. The crystallization of the Zr70-xNi14+xAl16 (x = 15 and 20 at.%) MGs proceeds by the nucleation and growth of Zr2Ni3Al5 and Zr6NiAl2 crystals. The crystallization sequence of the Zr70-xNi14+xAl16 (x = 0, 5, and 10 at.%) MGs can be concluded as follows: amorphous phase → amorphous phase + Zr2Ni3Al5 + ZrNiAl crystals → Zr6NiAl2 crystals. The crystallization kinetics of the initial and intermediate stages for the present system changes from the diffusion-controlled one-dimensional growth to two- and three-dimensional growth. Compared with the Zr70-xNi14+xAl16 (x = 15 and 20 at.%) MGs, the nucleation and growth during the initial crystallization of the Zr70-xNi14+xAl16 (x = 0, 5, and 10 at.%) MGs are relatively faster, which should be contributed to their lower activation energies for initial crystallization. The subsequent crystallization proceeds by a slower nucleation and growth compared with the Zr70-xNi14+xAl16 (x = 15 and 20 at.%) MGs, which should be suppressed by the endothermic phase transition from Zr2Ni3Al5 and ZrNiAl crystals to Zr6NiAl2 crystals. The present studies could give a complementary understanding on crystallization behaviors of metastable alloys.