Remarkable effect of Ce base element purity upon glass forming ability in Ce–Ga–Cu bulk metallic glasses

Abstract

Raw Ce element materials of eleven different purities are used to prepare bulk metallic glasses with the same nominal composition of Ce70Ga8Cu22 (at.%). In the high-purity regime of Ce (98.13–99.87wt.%), three distinct peaks are observed in the curve plotting the purity vs. the glassy rod critical diameter (Dc); and with ∼0.11 wt.% decrease in purity, the Dc can increase sharply from 1 to 10 mm. In the relatively low-purity regime of 96.15–98.13 wt.%, the low material purity is found to be beneficial for glass formation; and with a ∼0.61 wt.% decrease in purity, the Dc increases dramatically from 1.5 mm to at least 20 mm. Such a sensitive and systematic purity-dependent glass-forming ability has rarely been reported before in metallic glasses. It is also suggested that the high stability of the competing crystalline phases results from the mixture effect via addition of multiple impurity elements into the matrix glass-forming alloys, and that this addition of impurity elements may be the dominant factor responsible for their intrinsic glass-forming ability of these alloys. The results provide systematic evidence for the strong purity and composition effects that are present in glass formation, and can be used to shed light on scientific research and industrial applications in the field of metallic glasses.