Study On Effect Of AC Magnetic Field On Electric Property Of Al-Fe Binary Alloy Melt

The study shows that electromagnetic field can significantly affect the solidification structure of metal materials.Since the structure of materials solidification is determined by nucleation and growth which are closely related to the structure of the metal melt.The study that shows the effect of electromagnetic field on the microstructure of metal melt will be helpful to understand the solidification mechanism in the electromagnetic field.The pre-work of the project group showed that thermoelectric power and electric resistance,as sensitive physical parameters to metal melt structure,are used to study the effect of the AC electromagnetic field on the microstructure of metal melt.So based on this,this paper systematically studies the effect of AC electromagnetic field on the microstructure of Al-Fe alloys by measuring thermoelectric power and electric resistance.It provides basic data to understand the physical mechanism of alloy melt solidification behavior under the AC magnetic field deeply and optimize the effect.The article uses self-designed device that canreal-time synchronously detect thermoelectric power and resistance of molten metal in a variety of electromagnetic field.It focuses on the metal melt temperature,electromagnetic field frequency,excitation current,load time and the content of Fe in AC electromagnetic field.It also researches the effect of metal melt temperature on the quenching microstructure of Al-Fe alloys in AC electromagnetic field.Conclusions are as follows:(1)Compared with resistance,thermoelectric power is more suitable to characterize the structure of the metal melt in electromagnetic field.After closing the AC magnetic field,the thermoelectric power recovers and there are three stages:dramatic recovery,slow recovery and steady stage.(2)Thermoelectric power characterizes the effect of AC magnetic field on the structure of the Al-Fe metal melt and there is three characteristic parameters.The lasting variation Δu(t)is important parameters which characterize metal melt structure persistent change caused by electromagnetic field.The residual volume Δu is important parameters that reflect the residual changes caused by electromagnetic field.The time At takes to reach the stable stage is an important parameter that reflects the stability of melt structural changes caused by electromagnetic field.(3)The effect of AC magnetic field on the thermoelectric power of the Al-Fe alloys relates to the metal melt temperature,electromagnetic field strength,load time,electromagnetic field frequency and the content of Fe.With the increase of the temperature,the variation of thermoelectric power gradually increases,the time increases and then reduces.With the increase of the electromagnetic field strength,both the variation of thermoelectric power and the time gradually increase.With the increase of the load time,both the variation of thermoelectric power and the time increase rapidly and then tend to the stable state.With the increase of the load time,both the variation of thermoelectric power and the time of Al-Fe hypereutectic increase while the residual volume of hypoeutectic increases and then reduces.With the increase of the content of Fe,△U0、Δu(t)and Δt are gradually reduce while Δu slightly increases.(4)The AC magnetic field changed the microstructure of hypereutectic Al-2.45%Fe and Al-2.89%Fe alloy melt,A13Fe phase content was significantly reduced at the bottom of quenched samples of the alloy melt,and refined and homogenizied.However,a large number of appear primary A13Fe phase appeared at the top of the sample,and Fe element mass percent content increased.The more homogeneous distribution of A13Fe primary phase increases with the temperature increases.When the temperature is in the solid-liquid phase region,α-Al primary phase in the top of the specimens decreases with the effect of the AC magnetic field.When it is higher than the liquid temperature,α-Al primary phase in the top of the specimens enlarges with the effect of the AC magnetic field.(5)The effect of AC magnetic field on microstructure and thermoelectric power difference of hypereutectic Al-Fe alloy melt exsit a correspondence relationship,the higher change quantity of the thermoelectric power difference,the greater influence of the magnetic field on the microstructure and the macro distributionof components in the hypereutectic Al-Fe alloy melt.