| The Solidification refers to the phase transition process from liquid to solid state,which is widely used in material processing and preparation.With the development of solidification technology,not only the potential of traditional materials is further excavated,but also the technical means are provided for the development of new materials.Directional solidification technology and high magnetic field control technology both are concerned by more and more researchers because of their unique advantages.However,the systematic study of directional solidification under high magnetic field is less involved.Eutectic alloy tissue is simple,and it is also one of the relatively deep phase transition processes.In this paper,Eutectic Al-Fe alloy was selected as the research object.Alloy samples were obtained by directional solidification equipment under high magnetic field.The morphological evolution of growth rate and magnetic field intensity on eutectic tissue was explored,the growth and transformation mechanism of Al3Fe phase was analyzed,and the following main conclusions were drawn:(1)It is found that with the increase of growth rate,the eutectic tissue morphology is gradually transformed from the regular parallel layer distribution to the needle-like distribution morphology,and after the growth rate increases to a certain extent,the Eutectic region moves to the side of the high melting point phase because of the unbalanced solidification,which leads to the expression of the tissue morphology for the microstructure of the hypoeutectic.The Al3Fe phase of the eutectic tissue has undergone the transition from nonfacet to facet,and with the increase of the growth rate,the Al3Fe phase has experienced the change:flake-square bar-short round bar-spherical,which can be attributed to both internal and external factors.(2)It is found that with the increase of magnetic field intensity,the spacing of eutectic laminates decreases,and on the characteristic scale,the length and width of Al3Fe phase are basically decreasing with the increase of magnetic field strength,which shows that magnetic field has the function of refining grain.When the growth rate is small,the enhanced magnetic field can induce the Al3Fe phase to change from nonfacet to facet.When the growth rate is large,the reinforced magnetic field makes the transform from facet to nonfacet.The results of EBSD analysis show that the Al3Fe in the direction of{010} in the Eutectic Al-Fe alloy and the A1 in the direction of {110} have a parallel growth relationship.The magnetic field prompt the transformation of Al3Fe phase from facet to nonfacet by applying magnetism to the Al3Fe phase of the magnetic crystal anisotropy and the combination of Lorentz force and thermoelectric magnetism generated by the flow of the frontier melt of the Solidification interface(3)The growth rate and magnetic field intensity have similar effects on the growth of Al3Fe,which can be summed up as follows:When the growth rate is small and the magnetic field is not applied as a stable growth stage,the crystal growth mode is mainly influenced by the crystalline properties,and when the growth rate is increased or the magnetic field is strengthened,the increasing supercooling degree of the interface is When the conditions required for the growth of facet are reached,the crystal growth mode changes,and when the growth speed or magnetic field strength is further increased,the system has great energy and the interface is seriously unstable,which makes the Al3Fe aggregation and spheroidization. |
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