Non-equilibrium solidification character of Zr_(56.2)Ti_(13.8)Nb_(5.0)Cu_(6.9)Ni_(5.6)Be_(12.5) bulk metallic glass composites containing ductile dendrite phase

摘要

Bulk metallic glass (BMG) composites containing ductile phase were prepared by rapid water quenching of a homogenous Zr_(56.2)Ti_(13.8)Nb_(5.0)Cu_(6.9)Ni_(5.6)Be_(12.5) melt. The microstructure and composition of the materials were investigated by X-ray diffraction (XRD), optic microscopy (OM), and scanning electrion microscopy (SEM) attached with energy-dispersive spectroscopy (EDS). The secondary dendrite arm spacing (SDAS) in the composites was detected and the solidification parameters of this amorphous composites were obtained. The result shows that the composition of the dendrite phase is depleted in Ni, Cu and enriched in Zr, Nb and Ti, which strongly deviates from the nominal composition. SDAS is gradually increasing from the surface to the centre of the specimen, which inverses proportionally to cooling rate in Newton cooling type. With the increasing diameter of the samples, the secondary arm spacing gradually increases, except the specimen with the diameter of PHI 25 mm. Meanwhile, the relationship between SDAS and sample diameter or thickness is given quantitatively.