THE EFFECT OF SILICON ON THE GLASS-FORMING ABILITY OF THE CU47TI34ZR11NI8 BULK METALLIC-GLASS FORMING ALLOY DURING PROCESSING OF COMPOSITES

Composites of the Cu47Ti34Zr11Ni8 bulk metallic glass, reinforced with up to 30 vol % SiC particles are synthesized and characterized. Resul ts based on x-ray diffraction, optical microscopy, scanning Auger micr oscopy, and differential scanning calorimetry (DSC) are presented. Dur ing processing of the composites, a TiC layer forms around the SiC par ticles and Si diffuses into the Cu47Ti34Zr11Ni8 matrix stabilizing the supercooled liquid against crystallization. The small Si addition bet ween 0.5 and 1 at. % increases the attainable maximum thickness of gla ssy ingots from 4 mm for Cu-Ti-Zr-Ni alloys to 7 mm for Cu-Ti-Zr-Ni-Si alloys. DSC analyses show that neither the thermodynamics nor the kin etics of the alloy are affected significantly by the Si addition. This suggests that Si enhances the glass forming ability by chemically pas sivating impurities such as oxygen and carbon that cause heterogeneous nucleation in the melt. (C) 1988 American Institute of Physics.