Grain Refinement of Tough Pitch Copper by Electromagnetic Vibrations during Solidification

Abstract

Electromagnetic vibrations, which are generated by simultaneous imposition of a static magnetic field and an alternating electric field, were applied to the refinement of crystal grains of tough pitch copper. The electromagnetic vibrations of the frequency range from 100 Hz to 10 kHz were imposed during solidification of the copper rod. Within this frequency range, the vibration frequency of about 100 Hz was found to be the most effective in refining the copper crystal grains and the average grain size was refined up to 200 mm, which otherwise was around 600 mm in a nonvibrated specimen. It was concluded that by the electromagnetic vibration process tough pitch copper could also be refined as well as Al-Si alloys and AZ91D alloys.

Effect of Electromagnetic Vibration Frequency and Temperature Gradient on Grain Refinement of Pure Aluminum

“…It was supposed that grain refinement by the electromagnetic vibrations is hardly effective at the frequencies over 1 kHz. This effect of vibration frequency on the grain size is similar in tendency to the previous results on several alloy systems [24][25][26][27][28][29][30] and pure metals, 31,32) although the optimum frequency for refinement is different.…”

“…So there is possibility of application for refinement of pure metal. Indeed, it was reported that grain refinement of pure magnesium 31) and pure copper 32) was attained by using this process. However, it was considered that solidification parameters are severe for structural refinement of pure metals since there is hardly semi-solid state in the case of solidification of pure metals.…”

“…The effective frequency range for structural refinement of metallic materials was almost below the frequency of 1 kHz. [24][25][26][27][28][29][30][31][32] On the other hand, it was also reported that apparent glass-forming ability was enhanced by imposition of the electromagnetic vibrations with frequency of 5 kHz.…”

“…In the casting process accompanied solidification phenomenon, rapid cooling, [3][4][5][6] addition of refiners, [7][8][9][10][11][12] application of vibrations, [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] etc. are considered as a structural refinement method.…”

“…In contrast, the application of vibrations is able to refine microstructure even in bulk materials without a refiner. Mechanical vibration, such as mechanical mold vibration 13,14) or ultrasonic vibration, [15][16][17][18][19] and electromagnetic vibrations [20][21][22][23][24][25][26][27][28][29][30][31][32] are considered as an imposition method of vibrations. The application of mechanical vibrations such as ultrasonic ones enables not only refinement of the crystal grain, but also uniform dispersion of inclusion materials, degassing, improvement of metal feeding, etc.…”