Characteristics and evolution of microstructure in Cu-based bulk amorphous alloys

Bulk Cu₅₀Zr₄₂Al₈ amorphous coniform shape samples (10mm in diameter at bottom and 80mm in length) were successfully prepared by the arc-melting master alloy in the water-cooled copper crucible and then suck cast in the copper mold. Using the techniques of X-ray diffraction, Optical microscope, SEM and TEM analysis. The experimental investigation of the samples research of axial and radial characteristics and evolution of microstructure were conducted. Results indicated that along the temperature gradual direction, the cooling rate varied and the microstructure of coniform shape samples was composed of three portions as follows: the amorphous external region, which in the surface of the samples contact copper mold and the central crystal region, which in center of sample and the transition region, which locate between the amorphous region and the crystal region, which was composed of amorphous structure and crystal structure. The crystal size and volume fraction increase gradually inward from the surface.