A comparison of the crystallization behavior of liquid-quenched and vapor-quenched amorphous Cu60Ti40

The crystallization behavior of two Cu60Ti40 amorphous alloys, one prepared by a vapor-quench (VQ) process and one by a liquid-quench (LQ) process, has been studied using differential scanning calorimetry, X-ray diffraction, and transmission electron microscopy. Microstructural studies show that the two alloys have the same transformation sequence under similar annealing conditions. However DSC measurements of the crystallization temperature during isochronal annealing and of the incubation time for crystallization during isothermal annealing show that the LQ alloy is more thermally stable and therefore more structurally relaxed. TEM analysis of the partially annealed microstructures gives some insight into the mode of crystal nucleation and growth as a function of temperature. During isothermal annealing significant differences are observed for the two alloys in the shape and orientation of the crystals and in the crystal structure formed. Whereas the VQ alloy transforms polymorphicaly into the intermetallic Cu3Ti2, the LQ alloy forms the Ti-rich phase, Cu4Ti3. The two phases are closely related in structure and composition. The differences observed for the two alloys are discussed in terms of greater structural relaxation and short range order in the LQ alloy resulting from the mode of synthesis.