Zhenyuan Lu

Effect of a weak transverse magnetic field on the microstructure in directionally solidified peritectic alloys

Effect of a weak transverse magnetic field on the microstructures in directionally solidified Fe-Ni and Pb-Bi peritectic alloys has been investigated experimentally. The results indicate that the magnetic field can induce the formation of banded and island-like structures and refine the primary phase in peritectic alloys. The above results are enhanced with increasing magnetic field. Furthermore, electron probe micro analyzer (EPMA) analysis reveals that the magnetic field increases the Ni solute content on one side and enhances the solid solubility in the primary phase in the Fe-Ni alloy. The thermoelectric (TE) power difference at the liquid/solid interface of the Pb-Bi peritectic alloy is measured in situ, and the results show that a TE power difference exists at the liquid/solid interface. 3 D numerical simulations for the TE magnetic convection in the liquid are performed, and the results show that a unidirectional TE magnetic convection forms in the liquid near the liquid/solid interface during directional solidification under a transverse magnetic field and that the amplitude of the TE magnetic convection at different scales is different. The TE magnetic convections on the macroscopic interface and the cell/dendrite scales are responsible for the modification of microstructures during directional solidification under a magnetic field.

Influence of a transverse static magnetic field on the orientation and peritectic reaction of Cu-10.5 at.% Sn peritectic alloy

Peritectic alloy Cu-10.5 at.% Sn was directionally solidified at various growth speeds under a transverse static magnetic field. The experimental results indicated that the magnetic field caused the deformation of macroscopic interface morphology, the crystal orientation of primary phase along solidification direction, and the occurrence of peritectic reaction. The numerical simulations showed that the application of the magnetic field induced the formation of a unidirectional thermoelectric magnetic convection (TEMC), which modified solute transport in the liquid phase thereby enriching the solute concentration both at the sample and tri-junction scales. The modification of solidification structures under the magnetic field should be attributed to TEMC driven heat transfer and solute transport.

Thermoelectric–Magnetic-Convection-Induced Band-Structure Growth in Peritectic Alloys Directionally Solidified Under Static Magnetic Fields

AbstractThe formation of band structures in different peritectic alloys directionally solidified under transverse static magnetic fields was observed. Unidirectional thermoelectric–magnetic convection (TEMC), which modified solute transport in the liquid phase, was principally responsible for band-structure formation. A simple TEMC-regime-based model for predicting the compositional ranges in which band structures could form in alloys directionally solidified under transverse static magnetic fields was developed. The theoretical predictions agreed well with the experimental results.

Magnetic field induced band formation and crystal orientation in directionally solidified Cu-20 wt.% Sn peritectic alloys

The influence of a weak transverse magnetic field on the microstructure in directionally solidified Cu-20 wt.% Sn peritectic alloys at low speeds was investigated. Experimental results indicated that the magnetic field caused the evolution of the two-phase microstructure from coupled growth to band. Moreover, it was also found that the magnetic field induced the crystal orientation of the primary phase. The above results may be attributed to the effect of the magnetic field on the mass and heat transfer during directional solidification.