Atomic diffusion in liquid Al–Cu melt under static magnetic fields

Abstract

Atomic diffusion is a natural phenomenon in liquid melt. Avoiding the melt convection is the most challenging when accuracy in measuring the diffusion coefficient of atoms is desired. The diffusion in liquid Al–Cu melts is studied under various static magnetic fields (SMFs). Thermoelectric magnetic convection is induced during the diffusion in the conductive crucible. It is suppressed by increasing the magnetic flux density or eliminated by using an insulated crucible. The interdiffusion coefficient can be accurately measured in the SMF greater than 3 T. The present work provides a new view to study the solidification of alloys under the SMF.

Review on Eutectic-Type Alloys Solidified under Static Magnetic Field

“…The details of the GAAD apparatus can be found in Refs. [55,56]. Results demonstrated that the diffusionlimited condition as measured in microgravity was achieved when the MFD was greater than about 3 T. To further reveal the influence of this diffusive condition on crystal growth, Al-20wt.%Cu hypoeutectic alloy was solidified under a 24 T high SMF (Figure 3d-f) [61].…”

“…Studies have shown that the diffusion coefficient value decreases with the increase in MFD, which provides a simulated diffusive condition [52][53][54]. Recently, a novel gravityassisted automatic docking (GAAD) device was independently developed to measure the interdiffusion coefficient of an Al-Cu alloy (D AlCu ) from 0 T to 22 T and the critical MFD for achieving the diffusion-limited condition [55,56], as shown in Figure 3a-c. The details of the GAAD apparatus can be found in Refs.…”

“…Recently, magnetic dipole-dipole interactions (or magnetic interaction force) have been successfully used to affect grain growth, resulting in elongated grain and chainlike microstructures [40], and control the agglomeration and dispersion of primary crystals [51]. Therefore, the aforementioned forces, which have significant effects on the kinetic processes of solidification, are effective in controlling atom diffusion [52][53][54][55][56], nucleation events [42,57], melt convection [19,34], solute distribution [32,58,59], crystal migration [21,43,60], and morphology evolution [61][62][63] during solidification. Apart from kinetic processes, magnetic energy can also modify thermodynamic events, such as phase transformation and crystal orientation, even in a non-ferromagnetic system [12,64,65].…”

“…Indeed, the crystal orientation is considered to be influenced by the SMF in both thermodynamic and kinetic ways. In the past decade, our group has systematically investigated the role of SMFs in the solidification process, including atomic diffusion [55,56,66,67], dendrite growth [61,68], homogenization of the secondary phase in immiscible alloy [69][70][71], and electroslag remelting in steel [72][73][74]. Based on these studies, we suggested that ETA materials processing under an SMF holds promise for both fundamental scientific research and industrial applications.…”