Nucleation and Growth Behaviors of Primary Phase in Al-Cu Hypereutectic Alloy in High Magnetic Fields

Abstract

Abstract-The nucleation and growth of primary Al 2 Cu phase in the Al-34.3wt%Cu hypereutectic alloy without and with magnetic fields have been investigated by differential thermal analysis (DTA). The DTA curves indicated that the nucleation temperature of primary phase was significantly reduced in a magnetic field. The X-ray diffraction (XRD) patterns confirmed that the c-axes of primary Al 2 Cu crystals oriented along the direction parallel to a magnetic field. The microstructures showed that primary crystals aligned along a magnetic field and that their number distinctly increased with increasing a magnetic field as well. The suppression of nucleation in a magnetic field could be caused by the increase of the interfacial energy between the liquid and nucleus and the reduction of atom diffusion rates while the orientation of primary crystals were mainly attributed to both of the magnetic torque and the thermoelectric magnetohydrodynamic (TEMHD) flows.

Thermoelectric properties of crystal aligned higher manganese silicide fabricated by solidification under magnetic field

“…6) On the other hand, solidification under a magnetic field has also been reported to directly yield crystal aligned structures in various alloys. [20][21][22][23][24][25][26][27][28][29][30][31][32] Iwai and Usui 20) showed that the c-axis of the Bi-rich primary phase in Bi-10 mass % Sn alloys can be aligned by simply applying a 8 T magnetic field during solidification. Legrand et al 21) succeeded in forming highly c-axis aligned Sm-Co alloys by applying a 2.5 T magnetic field during rapid solidification.…”

“…The c-axis alignment of primary MnBi in the Bi-Mn system with various Mn contents solidified under a magnetic field has been studied by several groups. [22][23][24][25][26] Li et al 27) solidified a Al-34.3 mass % Cu alloy under 2-12 T magnetic fields and observed a c-axis alignment of Al 2 Cu crystals increasing proportionally to magnetic field intensity. Usui et al 28) reported that crystal alignment of Sn-Pb alloy is possible by directly applying a magnetic field of 7.5 T during solidification when the primary Sn-rich phase was dispersed by electromagnetic oscillation.…”