%0 Journal Article
%T Spheroidization behavior of dendritic b.c.c. phase in Zr-based モ-phase composite
%A Sun Guoyuan
%A Li Ping
%A Chen Wei
%J China Foundry
%D 2013
%I Foundry Journal Agency
%X The spheroidization behavior of the dendritic b.c.c. phase dispersed in a bulk metallic glass (BMG) matrix was investigated through applying semi-solid isothermal processing and a subsequent rapid quenching procedure to a Zr-based モ-phase composite. The Zr-based composite with the composition of Zr56.2Ti13.8Nb5.0Cu6.9Ni5.6Be12.5 was prefabricated by a water-cooled copper mold-casting method and characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that the composite consists of a glassy matrix and uniformly distributed fine dendrites of the モ-Zr solid solution with the body-centered-cubic (b.c.c.) structure. Based on the differential scanning calorimeter (DSC) examination results, and in view of the b.c.c. モ-Zr to h.c.p. メ-Zr phase transition temperature, a semi-solid holding temperature of 900 ━C was determined. After reheating the prefabricated composite to the semi-solid temperature, followed by an isothermal holding process at this temperature for 5 min, and then quenching the semi-solid mixture into iced-water; the two-phase microstructure composed of a BMG matrix and uniformly dispersed spherical b.c.c. モ-Zr particles with a high degree of sphericity was achieved. The present spheroidization transition is a thermodynamically autonomic behavior, and essentially a diffusion process controlled by kinetic factors; and the formation of the BMG matrix should be attributed to the rapid quenching of the semi-solid mixture as well as the large glass-forming ability of the remaining melt in the semi-solid mixture.
%K bulk metallic glass composite
%K semi-solid isothermal processing
%K spheroidized microstructure
%U http://www.foundryworld.com/uploadfile/2013040254336233.pdf