Effects of Cooling Rates on Glass Formation and Magnetic Behavior for the Fe_73.0C_7.0Si_3.3B_5.0P_8.7Mo_3.0 Bulk Metallic Glass

In this paper, effects of cooling rates on glass formation and magnetic behavior of the Fe_73.0C_7.0Si_3.3B_5.0P_8.7Mo_3.0 (at. pct) alloy were investigated via different purging gases (i.e., helium and argon) during suction casting. X-ray diffraction patterns and transmission electron microscopy characterization confirmed that the maximum attainable diameter for glass formation is increased from 5 to 7 mm with the helium as the purging gas, relative to the argon. Meanwhile, the coercivity value (H _c) of the sample cast in helium is almost 5 times larger than that fabricated in argon, although the magnetization saturation in these two alloys is similar. Our pair distribution function analysis, density, and positron annihilation lifetime spectroscopy measurements indicated that the sample cast in helium possesses more free volume; however, the difference between them is insubstantial. Further, experimental results revealed that the residual stress in the samples cast under helium is much larger than that in those prepared in Argon, which could be responsible for the abrupt change in the coercivity.