Structure Evolution of Bulk Metallic Glass Zr52.5Ni14.6Al10Cu17.9Ti5 during Annealing

Bulk metallic glass Zr52.5Ni14.6Al10Cu17.9Ti5 was prepared by melt injection casting method. Its glass transition and crystallization temperatures were determined by differential scanning calorimetry (DSC) to be 631 K and 710 K respectively. By analysis of X-ray diffractometry (XRD) and transmission electron microscopy (TEM), the predominant crystallized phase of Zr2Ni0.67O0.33 distributed an glass state matrix was detected after annealing at 673 K for 600 s. The transformation to Zr2Ni0.67O0.33 and a small amount of ZrAl and Zr2Cu took place after annealing for 600 s at temperature from 703 K to 723 K. With increasing annealing temperature from 753 K to 823 K, the amounts of ZrAl and Zr2Cu increased, but the size of the crystals did not significantly change. The transformation to Zr2Ni0.67O0.33 is interface-controlled, but is diffusion-controlled to Zr2Cu and ZrAl. With increasing annealing temperature up to 200 K above T-x, the nanometer grains became very fine because of the increase of nucleation rate for Zr2Cu and ZrAl.