This article discusses the effect of temperature field on the Pulse Magneto-Oscillation(PMO) induced solidification refinement of pure aluminium to provide more information for the industrial application of the PMO solidification technology.The temperature field is altered mainly by applied variable cooling conditions and pulse parameters.Experimental results show that the refinement effect in the case of full sand mould applied is weakened with the decreasing of cooling rate,however,in the alternative case,the sand mould whose sand bottom was replaced by a graphite block is favorable to the survival of equiaxed nucleus.The refinement mechanism is discussed in terms of the relationship between temperature field and the formation process of solidified structure.The formation or survival of nucleus depends on both temperature field and Joule heat produced by PMO,both low pulse frequency and high pulse current were experimentally confirmed to be effective;and PMO was demonstrated high potential in industrial application.
Li BoYin ZhenxingGong YongyongLJ KefengZheng HongxingLi RenxingZhai Qijie
Pulse magneto-oscillation (PMO) was developed as a novel technique to refine the solidification structure of pure aluminium.Its grain refining mechanism was proposed.The PMO refinement mechanism is that the nucleus falls off from the mould wall and drifts into the melt under the action of PMO.The solidification structure of Al melt depends on the linear electric current density,and also the discharge and oscillation frequencies.The radial pressure of PMO sound wave is the major factor that contributes to the migration of nucleus into the melt.
Pulsed magneto-oscillation （PMO） as a new electromagnetic technology to generate the grain refinement in metals and alloys was significantly developed in recent years. The influence of electromagnetic parameters on the grain size reduction in pure AI was investigated under the application of PMO with a constant inputting power. The experimental results show that the grain refinement degree could be improved with the increase in the current intensity in the case of the identical power. Moreover, through analysing the electromagnetic force and resistance force applied on the nucleus, a criterion of the nucleus detached from the mould wall was constructed. Based on the criterion, the detachment of nuclei with finer radius could cause better effect of the grain refinement, when applying a higher current peak. The movement of the detached grains was considered by analysing the influence of electromagnetic force and forced flow.
