Effect of Electromagnetic Vibrations on Fe-Co-B-Si-Nb Bulk Metallic Glasses

Abstract

It is known that cooling rate from the liquid state is an important factor for producing the bulk metallic glasses. However, almost no other factors such as electric and/or magnetic fields were investigated. The present authors have reported that a new method for producing Mg-Cu-Y bulk metallic glasses by using electromagnetic vibrations is effective in forming the metallic glass phase. Moreover, the present authors have reported that the glass-forming ability of Fe-Co-B-Si-Nb alloys also is enhanced with increasing the electromagnetic vibration force. Thus, this study aims to investigate effects of the electromagnetic vibrations on Fe-Co-B-Si-Nb bulk metallic glasses in order to investigate further. Half round lines which consist of fine crystal particles in a glassy phase were observed in the boundary part of the molybdenum electrode for the alloy with the electromagnetic vibrations. It was considered that the reactants of the molybdenum electrode which were solid at 1573 K were moved into the sample by the electromagnetic vibrations and caused the nuclei of crystal particles which composed the half round lines. If tungsten was used as the electrodes, there was no influence of electrodes in the center of the samples. When molybdenum or tungsten was used as the electrodes, the effect of the electromagnetic vibrations was found to be the same, namely the electromagnetic vibrations act on decreasing the number of crystal nuclei.

Production of Zr-Based Metallic Glass Matrix Composites by Semisolid Process

“…This result is the same as the result of XRD. It is considered that heterogeneous crystalline nuclei exist in the liquid region when heat treatment temperature is close to the solidus temperature [16][17][18][19][20][21][22][23][24]. Thus, it is presumed that heterogeneous crystalline nuclei related to unknown crystalline phase decrease the glass forming ability for the samples heat treated at low temperatures.…”

Motion of Crystal Particles by the Electromagnetic Vibrations in Mg-Cu-Y Bulk Metallic Glasses

“…However, this increase in the cooling rate disappears with electromagnetic vibrational frequencies of more than 10 kHz. [15][16][17] It was found that the absence of macroscopic stirring resulted in the disappearance of the increase in the cooling rate because of the nanometer-sized amplitudes at higher frequencies. When particles in the liquid metal have lower electric resistance than the liquid metal, these particles are considered to vibrate vigorously in the liquid metal by Lorentz force, because the electric current concentrates in those.…”

Effect of Purity and Superheating on the Glass-Forming Ability of Mg-Cu-Y Alloys by an Electromagnetic Vibration Method

“…The second effect is the decrease in the number of crystal nuclei. [12][13][14] If it is supposed that only the alloy sample exists in the free space and that the electric current is passed through the sample uniformly, the electromagnetic vibrations are the vibrating motion and not waves like the ultrasonic waves. However, when particles in the sample have lower electric resistance than the molten sample, these particles are considered to vibrate vigorously in the molten sample by Lorentz force because the electric current concentrates in those.…”