Ti--BASED AMORPHOUS COMPOSITES WITH QUANTITATIVELY CONTROLLED IN--SITU FORMATION OF DENDRITES

Abstract

A series of (Ti32.8Zr30.2Ni5.3Cu9Be22.7)100−x (Ti61.5Zr36.4Cu2.1)x (x=10—95) bulk amorphous composites with quantitatively controlled in–situ formation of bcc–dendrites were prepared. The microstructures were analyzed by SEM, XRD and TEM. Thermal behaviors were examined using DSC. The results show that the size and volume fraction of dendrites depend on x in the composites. With increasing x, the volume fraction of dendrites rises monotonically from 20% to 90%. The microstructural transition between the matrix and the dendrites is smooth and successive with no phases observed at the interface. Compression tests show the size and volume fraction of dendrites largely influence the mechanical properties of composites. When the volume fraction is larger than the critical value (approximately 30% in the present work), the plasticity of composites cannot be improved. When the volume fraction is over the critical value, the higher the volume fraction of dendrites, the larger the plastic strain, the stronger the work hardening capacity. It implies that the properties of composite can be mediated by the tunable volume fraction of dendrites. These findings are significant to develop the controllable microstructure and performance materials. When x=90, the plastic strain and the compressive strength of the composites reach 14.4% and 1917 MPa, respectively.