The use of various external influences to influence metal melts (vibration, ultrasound, etc.) is a known method of changing the structure and properties of metals and alloys. In the overwhelming majority, all methods of external action on melts cause grinding of the metal structure, which leads to an increase in strength characteristics. The paper considers a new method of external physical action on molten metal, namely, electromagnetic pulses. Work on the investigation of the impulse effect on metal melts is conducted in two laboratories: in Chelyabinsk (the laboratory of Professor Krymsky V.V.) and in Khabarovsk (in the laboratory of Ri Josen). If at the beginning only small masses of metal were processed in the laboratory, now the work is at the industrial level. Masses of processed metal reach 2 tons. The article summarizes and structures the results of the conducted studies on the effect on nonferrous metal melts with powerful electromagnetic pulses. General regularities of such influence on the structure and properties of the metal are established. The results of such effects on pure metals (aluminum, zinc) and on aluminum alloys are provided. It is established that impulse processing contributes to a decrease in the porosity of castings, an increase in metal density, and a decrease in electrical resistivity. Also, in pulsed processing, a grinding of the metal grains occurs, an increase in the solubility of the main components in the alpha phase, and changes for the eutectic in the structure. An interesting fact is the simultaneous increase in the properties of the strength and plasticity of the metal.
The results of experiments on the impact of high power electromagnetic pulses (EMP) on the metal alloy melts are discussed. A generator with the following pulse parameters: the amplitude of 10 kV, the duration of 1 ns, the leading edge of 0.1 ns, repetition rate of 1 kHz was used for pulse electric treatment of metal melts. The maximum network input of the generator equals 100 watts. The treatment was carried out in a furnace immediately before casting. The treatment of the melt by electromagnetic pulses is conducted for 10-15 minutes. Comparative analysis of treated and untreated samples showed a change in structure, density, strength, ductility, and toughness of the cast metal. The mechanism of stepping impact on the metal melts was discussed. Analysis of the results of other external physical melt impact methods showed that the overall match is observed with the results of the ultrasonic treatment of metals. Therefore, the hypothesis of the pulse ultrasonic shock wave generation at the front was accepted as the basis-hypothesis for the mechanism of the impact of electromagnetic pulses on the melt. In the theoretical part of the paper a model of electromagnetic pulses conversion in acoustic pulses is proposed.
There are results of industrial experiments in steel 35L treatment with electromagnetic pulses (EMP) available. The results evidentiate significant improvement in the complex of metal mechanical properties after such treatment. The theory, describing impulse action on metals is proposed herein.
High entropy alloys (HEAs) are among the most promising materials, owing to their vast chemical composition window and unique properties. Segregation is a well-known phenomenon during the solidification of HEAs, which negatively affects their properties. The electromagnetic pulse (EMP) is a new technique for the processing of a metal melt that can hinder segregation during solidification. In this study, the effect of an EMP on the microstructure and surface properties of Al0.25CoCrFeNiV HEA is studied. An EMP, with an amplitude of 10 kV, a leading edge of 0.1 ns, a pulse duration of 1 ns, a frequency of 1 kHz, and pulse power of 4.5 MW, was employed for melt treatment. It was found that the microstructure of Al0.25CoCrFeNiV HEA changes significantly from dendritic, for an untreated sample, to lamellar “pearlite-like”, for an EMP treated sample. Moreover, EMPs triggered the formation of a needle-like σ-phase within the solid solution grains. Finally, these microstructural and compositional changes significantly increased the microhardness of Al0.25CoCrFeNiV HEA, from 343 ± 10 HV0.3 (without the EMP) to 553 ± 15 HV0.3 (after the EMP), and improved its resistance against gas-abrasive wear. Finally, an EMP is introduced as an effective route to modify the microstructure and phase formation of cast HEAs, which, in turn, opens up broad horizons for fabricating cast samples with tailorable microstructures and improved properties.
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