The glass-forming ability of Pr–Ni–Al bulk metallic glasses

A series of Pr–Ni–Al bulk metallic glasses (BMGs) was prepared by a copper mold casting method. The effect of the alloy composition on the glass transition temperatures (Tg) and supercooled liquid regions (ΔTx) was studied. It showed that the increase in Pr content to a certain degree, though at which the alloy remained fully amorphous, caused the disappearance of Tg and ΔTx. Continuous and isothermal annealing methods were used to investigate the disappearance mechanism of Tg and ΔTx on the representative Pr55Ni25Al20 and Pr65Ni25Al10 BMGs. X-ray diffraction (XRD) analysis on crystallization products showed that the disappearance of Tg and ΔTx for Pr65Ni25Al10 was not due to the precipitation of different kinds of crystalline products but due to the decrease in glass stability (GS) resulted from the larger quantities of the first precipitating Pr7Ni3 phase at relative lower temperatures. As a whole, the alloy composition dependence of Tg and ΔTx was also discussed in the framework of the three empirical rules for achievement of high glass-forming ability glasses.