Zhu Zhengwang

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

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.

EFFECT OF W FIBER DIAMETER ON THE COMPRESSIVE MECHANICAL PROPERTIES OF THE Zr-BASED METALLIC GLASS COMPOSITES

The Zr-based metallic glass composite containing four kinds of W fibers with different diameters are prepared by infiltration casting method.The diameters of the W fibers are 1000,700,500 and 200μm,respectively.The effect of fiber diameter on the quasi-static and dynamic compressive mechanical properties and deformation behaviors of the composites was investigated.The results show that the quasi-static compressive properties improve with the decrease of the W fiber diameters,which is attributed to the increasing interface area and the size effect of the metallic glass matrix.Under dynamic compressive loading,the strain rate changes with the variation of the W fiber diameter at the same bullet firing pressure.The dynamic compressive strength and strain rate sensitivity exponent of the metallic glass composite with a fiber diameter of 500 μm is the highest among the four W fiber/Zr-based metallic glass composites.