Study On Growth Behaviours Of Intermetallic Compounds In Binary Sn And Al Alloys Under A High Magnetic Field

In this work,Sn-1.5wt.%Mn,Sn-1.3wt%Co and Al-6wt.%Sr alloys were solidified in non-directional ways without and with high magnetic fields.The morphologies and crystallographic characteristics of tetragonal primary MnSn2,CoSn2 and Al4Sr phases were studied in detail by EBSD technique.The mechanism of high magnetic fields on the orientation and alignment of these primary phases was analyzed.The morphologies and crystallographic characteristics of primary phases:1)the primary MnSn2 phase has shapes of octagonal and quadrangular prisms.They prefer growing in the direction of<001>and their ends are coronal.The crystallographic planes on the sides of the octagonal MnSn2 phase are {110} and {100},while those on the sides of the quadrangular MnSn2 phase are {110}.The high growth rate caused by the low atomic density at the atomic scale is the main kinetic reason of the disappearance of the {100} planes of the MnSn2 phase;2)the primary CoSn2 phase of the tetragonal structure is quadrangular,and the crystallographic planes of the lateral and bottom sides of CoSn2 are {110} and {001},respectively.Due to the nonequilibrium peritectic reaction(L+CoSn2?CoSn4),with the primary CoSn2 phase as the core,a metastable CoSn4 phase with an orthogonal structure is formed around the phase({001}CoSn4//{001}CoSn2;[100]CoSn4//{110}CoSn2).The peritectic CoSn4 phase has a tabular shape.Its large facets correspond to {001} and the side facets{111?.Since the {001} crystal plane produces a large number of steps,the CoSn4 phase grows in a spiral manner;3)The tetragonal Al4Sr phase has a large three-dimensional shape.The crystal plane corresponding to the large surface is {001},and the crystal plane enclosing the side surface is {011}.The morphologies of the primary MnSn2 phase,the primary CoSn2 phase,the peritectic CoSn4 phase and the primary Al4Sr phase are all related to the difference in crystal growth rates induced by the reticular(atomic)density in the atomic scale.The influence of high magnetic fields on the alignment and orientation of the primary phases:1)the paramagnetic primary phase MnSn2 align regularly in the direction perpendicular to the magnetic field along the long axis,and its<110>direction tends to orient preferentially in the the magnetic field direction;2)the paramagnetic primary phase CoSn2 align regularly with the long axes parallel to the magnetic fields,and its<001>direction tends to orient preferentially in the the magnetic field direction.At the same time,the magnetic viscosity resistance induced by the high magnetic fields alleviates the gravity segregation of the primary CoSn2 phase and peritectic CoSn4 phase;3)the large plane of the diamagnetic primary Al4Sr phase tends to align in the magnetic field direction,and its<001>direction tends to orient preferentially in the direction perpendicular to the magnetic field.At the same time,the magnetic viscosity resistance induced by high magnetic field tends to eliminate the gravitational segregation of the primary Al4Sr phase.The alignments and preferential orientations of the primary MnSn2,CoSn2 and Al4Sr phases are all related to the magnetization energy and the magnetic torque induced by high magnetic fields.The research of this subject enriches the law of solid-phase transformation of binary alloys under high magnetic fields,and provides a new research idea for study of the growth behaviors on intermetallic compound phases to some extent.