Crystallization characteristics of an amorphous Ti80Si20 alloy at high pressures

Abstract

Amorphous Ti-20 at% Si alloy, prepared by rapid quenching from the molten state, was annealed while being subjected to a pressure of 10GPa. X-ray diffraction investigations on the alloy specimens quenched to ambient conditions have shown that pressure greatly alters the crystallization characteristics and a body-centered cubic solid solution having the same composition as that of the parent amorphous matrix forms preferentially at temperatures in the range from 400 to 550° C. The lattice constant of this supersaturated solid solution suggests that silicon atoms are dissolved substitutionally in the titanium lattice. It is not until the temperature is raised to above 550° C that the amorphous matrix decomposes into a bcc solid solution containing less amount of silicon and a silicon-rich phase. Discussion is given on the mode of crystallization on the basis of the present results and those of previous studies and it has been shown that the crystallization of amorphous alloys can be classified into three types depending on pressure and temperature.