Comparative study of bulk metallic glass composites with high-yolume-fractioned dendritic and spherical b. c. c. phase precipitates

A dendritic beta-phase reinforced bulk metallic glass (BMG) composite named as D2 was prepared by rapid quenching of a homogenous Zr60Ti14.67Nb5.33Cu5.56Ni4.44Be10 melt, and characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) observation and room-temperature compression test. The microstructure and mechanical properties were compared with those of the spherical beta-phase reinforced composite named as composite S2. It was found that the composite D2 contains beta-phase dendrites up to 56% in volume-fraction, and exhibits a ductile compressive behavior with plastic strain of 12.7%. As the high-volume-fractioned beta-phase dendrites transferred to coarse spherical particles of about 20 mu m in diameter in the composite 52, a much improved plastic strain up to 20.4% can be achieved. Micrographs of the fractured samples reveal different interaction modes of the propagating shear bands with the dendritic and spherical beta phase inclusions, resulting in different shear strains in the composite samples. The matrix of composite S2 undergoes a significantly larger shear strain than that of the composite D2 before ultimate failure, which is thought to be mainly responsible for the greatly increased global plastic strain of the S2 relative to D2.