Abstract
The internal coupled electromagnetic melt treatment (ICEMT) method is firstly proposed to produce high-quality and large-sized aluminum alloy billets. A three-dimensional model was established to describe the ICEMT process of direct chill casting (DC casting). The effect of ICEMT on the fluid flow patterns and temperature field in the DC casting of ϕ880 mm AA2219 billets is numerically analyzed. Moreover, the mechanisms of the ICEMT process on grain refinement and macrosegregation were discussed. The calculated results indicate that the electromagnetic field appears to be coupled circinate at the cross section of the melt, the fluid flow becomes unstable accompanied by the bias flow, and the temperature profiles are significantly more uniform. An experimental verification was conducted and the results prove that compared with traditional direct chill casting, the microstructures of the AA2219 large-scale billet under the ICEMT process are uniform and fine.
Highlights
DC casting is an efficient way to produce large-sized Al-alloy billets but there remain a few problems to be considered
Waheed [16] analyzed the effects of billet diameters on flow pattern under the thermal convention in DC casting by using the low Reynolds numbers velocity variance-elliptic relaxation (Re ν2 -f) turbulence model and the results showed that the increase in billet diameter deepened the flow penetration, weakened the recirculating vortex, and deepened the sump depth, which means that the larger the Al-alloy billet, the more the defects in the billet
Frequency changes from 5 Hz to 20 Hz at a height of 100 mm below the inlet of melt at a given time. It differs from normal distributions of magnetic induction intensity induced by electromagnetic stirring (EMS) outside the melt
Summary
AA2219 has many advantages including high specific strength, high fracture toughness, high corrosion resistance, and excellent weldability, which has been broadly applied in many fields such as aerospace, defense, and military [1,2]. AA2219 itself has a few shortcomings such as high copper content and wide temperature range of solidification, from approximately 913 K to 816 K, resulting in worse problems such as coarser and inhomogeneous structures, more serious macrosegregation, and coarser second phases in the large-sized billets. Those defects that cannot be improved in subsequent processing such as forging and rolling, are very harmful to mechanical property in service [3]. Those unrecoverable defects usually become much worse with the increase in billet diameter in the DC casting process [4]
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