| Eutectic alloys play an important role in metal and alloy systems.The eutectic alloy has a low melting point and excellent flow properties,and has broad prospects in manufacturing and application.As a non-contact extreme physics field,a strong magnetic field can apply energy to the atomic scale without contact.Material science under magnetic field has attracted the attention of researchers as an emerging discipline.The coagulation process of eutectic alloys is studied.The effects of magnetic field on the growth interface stability,eutectic growth and crystal orientation of eutectic alloys are investigated.The role of magnetic field in the solidification process of eutectic alloys are investigated.It is important to study the theory of solidification.Guiding significance.In this paper,the directional solidification technique was used as the research method.The Al-Fe eutectic alloy was used as the object.The solidification rate,the constant magnetic field and the gradient magnetic field were observed by means of optical microscopy,EBSD and scanning electron microscopy.Evolution and stability of solid/liquid interface stability,and analysis of the mechanism of action of strong magnetic fields.The main research results are as follows:(1)Under the condition of no magnetic field,the solidified structure is evenly arranged on the substrate along the direction of directional solidification.With the increase of growth rate,the lamellar structure transforms into a bar shape,and the phase spacing of Al3Fe phase decreases significantly.When the growth rate is 100 ?m/s,the solidified structure consists of eutectic ?-Al and Al-Al3Fe eutectic clusters,which are evenly distributed along the direction of solidification,and the microstructure changes significantly.(2)With the increase of magnetic induction intensity,the stability of solid/liquid interface shows a trend of increasing and then weakening,and the phase distance of Al3Fe phase in the stable growth region decreases gradually.Through the observation of the solidification structure perpendicular to the magnetic field,it is found that the Al3Fe phase is orderly distributed on the matrix after the application of 6 T high magnetic field;when the magnetic induction intensity increase to 12 T,the solidification structure begins to change to cellular structure.The analysis shows that the high magnetic field restrains the convection in the liquid phase and weakens the lateral diffusion of solute atoms.When the magnetic induction intensity reache to 12 T,the solute concentration at the solid/liquid interface increases and the stability of the solid/liquid interface is destroyed under the magnetization force.(3)When the growth rate reache to 100 ?m/s,the solid/liquid interface presents a convex interface.There is no obvious regularity between the change of solid/liquid interface morphology and the change of magnetic induction intensity.Through the observation of solidification structure parallel to and perpendicular to the magnetic field,it is found that the magnetic field inhibits the diffusion of solute.In the direction parallel to the magnetic field,the size of Al3Fe phase at the edge of the cellular eutectic decreases gradually;in the direction perpendicular to the magnetic field,the cellular eutectic has a tendency of "fusion",and the area of the cellular eutectic increases.(4)By observing the solidification structure in the semi-solid region,it is found that the lower the growth rate,the larger the size of Al3Fe phase in the semi-solid region.With the increase of growth rate,the existence time of semi-solid region decreases.In this time interval,Al3Fe phase can not be broken sufficiently,so the aggregation degree of Al3Fe phase at the bottom of the sample decreases.(5)After applying a high gradient magnetic field,the solute atoms move downward due to the magnetization force,which inhibits the solute convection in the liquid phase,making it difficult to migrate the solute atoms.In the solidification process,due to the enrichment of solute atoms at the front of solid/liquid interface,the nucleation number of Al3Fe phase increased,so the size of Al3Fe phase decreased significantly,and the interphase distance decreased.After the application of a high gradient magnetic field,the morphology of the solidified structure showed a cell eutectic?cluster eutectic?lamellar eutectic?dendritic transition. |
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