No abstract

Zr 65 Al 7:5 Ni 10 Cu 12:5 Ag 5 ingots with different microstructures are obtained by changing the number of the repeated arc melting times. Differential scanning calorimetry (DSC) traces show that when the microstructure of the mother ingot becomes finer, the thermal stability of the glassy alloy improves during the crystallization of the glass. Because of the structure heredity, the finer the mother ingot microstructure is, the smaller the average size of the (Zr,Ag)-rich short-range orders in the glassy alloy is. The decrease of the size of the short-range orders makes the rearrangement of the elements more difficult in the glassy alloy. As a result, the activation energy for precipitation and decomposition of the Iphase becomes higher.

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This paper investigates the crystallization kinetics of Zr 60 Al 15 Ni 25 bulk glassy alloy under isothermal annealing by differential scanning calorimetry (DSC). The results show that the incubation time is very small even at low annealing temperature (743 K) and increases slightly with the annealing temperature decreasing, which suggests a growth-controlled crystallization process. However, the exothermic peak width, reflecting the time for the actual crystallization process, increases greatly when annealing temperature decreases. The Avrami exponents indicate that the crystallization mechanism changes at different annealing temperatures. The change of the crystallization mechanism is attributed to the great difference of the mobility ability of atoms at different temperatures.