Effect Of Electromagnetic Stirring On Microstructure Of Al-5Ti-1B Master Alloy

With the extensive application of aluminum alloys,the requirements for the performance of aluminum alloys are also increasing.Fine and uniform grain is the guarantee for good comprehensive performance of metal materials.Grain refiner is an effective and convenient way to achieve this goal.At present,Al-5Ti-1B master alloy is the most widely used aluminum alloy refiner.The second phase TiAl₃ particles are too coarse and the TiB₂ aggregate into clusters,these problems seriously affect the performance of the Al-5Ti-1B master alloy.Electromagnetic stirring is expected to improve the performance of Al-5Ti-1B master alloy.The influence of electromagnetic stirring on Al-5Ti-1B master alloy is studied in this paper.In order to improve the performance of Al-5Ti-1B alloy,the electromagnetic stirring device was designed on the basis of the principle of rotating magnetic field electromagnetic stirring.The parameters of electromagnetic stirring were determined.The rotating magnetic field was simulated by Ansoft Maxwell software.The distribution of magnetic force line and electromagnetic induction intensity with stirring frequency were obtained.The movement of the melt in the magnetic field was analyzed.The flow speed of melt from the inside to the outside increases first and then decreases.Subsequently,the effect of electromagnetic stirring frequency on the microstructure of master alloy was studied.The main phase composition of Al-5Ti-1B master alloy prepared by fluoride salts method was examined.There are TiAl₃ and TiB₂except aluminum matrix.Electromagnetic stirring can effectively control the size and distribution of TiAl₃ in the master alloy,and improve the aggregation of TiB₂.Compared with the Al-5Ti-1B master alloys prepared without electromagnetic stirring,the average diameter of TiAl₃ decreases significantly.The phenomenon of local aggregation of TiAl₃ disappears and it is evenly distributed on the aluminum matrix.The aggregation chain of TiB₂ becomes shorter at the grain boundaries of?-Al,and the diameter of condensed clusters on aluminum matrix decreases.With the increase of electromagnetic stirring frequency,the TiAl₃ particles become smaller and the distribution is more uniform.The aggregation chain at the?-Al grain boundary and the aggregation group average diameter of TiB₂ also becomes shorter.However,with the increase of electromagnetic stirring frequency,the size of the second phases in the core of the Al-5Ti-1B alloy first decreases and then increases,and it is the smallest at 5Hz.Under the experimental conditions of this paper,the optimal electromagnetic stirring frequency is 5Hz.The main reason of electromagnetic stirring refining TiAl₃ is that TiAl₃ particles are broken by electromagnetic force,and is distributed uniformly by melt flow.The improvement of TiB₂ aggregation is mainly due to the increase of energy,so that some TiB₂ can be separated from the original agglomerate.Therefore,electromagnetic stirring can reduce the agglomeration size of TiB₂.