Mechanism of Electromagnetic Field in the Sub-RapidSolidification of High-Strength Al-Cu-Li Alloy Produced by Twin-Roll Casting

Shiju Li,Chen He,Zhaodong Wang,Yong Li,Guangming Xu,Bowen Wei,Wei Yu

doi:10.3390/met11060952

Abstract

In this work, a Al-Cu-Li alloy plate with outstanding mechanical properties was successfully prepared with electromagnetic twin-roll casting (TRC) technology. The microstructure of Al-Cu-Li alloy manufactured by conventional mold casting, TRC, and electromagnetic TRC was studied in detail. The action mechanism of electromagnetic oscillation field (EOF) in the TRC process was studied by systematic experimental characterization and numerical simulation. The results show that the EOF will enlarge the circumfluence area in the cast-rolling zone, accelerate the mass transfer and heat transfer in the molten pool, and make the solute field and flow field in the liquid cavity tend to be evenly distributed. Further, the introduction of the EOF will produce the electromagnetic body force F with the maximum strength of 14 N/m3. The F acting on the solidification front will eliminate the accumulation and deposition of Cu2+, Li+, Mg2+, Zn2+, Mn2+ at the dendrite tip and inhibit the growth of dendrites. At the same time, the F can refine the microstructure of the TRC plate, promote the formation of equiaxed crystals, improve the supersaturated solid solubility of solute elements in the α(Al) matrix, and avoid the appearance of obvious solute segregation area or the formation of excessive solute enrichment area. Therefore, the macro-segregation in TRC plate was significantly reduced, the solidification structure was dramatically refined, and the comprehensive properties of the alloy were remarkably improved.

Highlights

The macrosegregation band made the comprehensive properties of the alloy plate worse, and it cannot be removed by a subsequent heat treatment process, so it is important and significant to solve macro-segregation at the source area [20,21,22]
After the electromagnetic oscillation field (EOF) was introduced in the twin-roll casting (TRC) process, the macro-segregation zone in the plate was effectively eliminated, and the solidification structure of the alloy was further refined, and the average secondary dendrite arm spacing (SDAS) was reduced to 6.90 μm
Where Cs and CL is the solute concentration in solid phase and liquid phase, respectively; K

Summary

Introduction

Compared with conventional Al alloys, Al-Li alloys have the advantages of low density, high specific strength, and high specific stiffness, which make them extensively used in the aerospace and military fields [1,2,3,4]. Al-Cu-Li alloys have the above excellent properties of Al-Li alloys, and excellent fracture toughness, weldability, and corrosion resistance [5,6]. Al-Cu-Li alloys have become the most potential alloy series in the 3rd generation of Al-Li alloys. These alloys have been widely used in industry. Al-Cu-Li alloy AA2195-T83 extrusion replaced 7050-T7451 in the internal fuselage structure of the Airbus A380 [8]

Methods

Results

Conclusion