Effect of low frequency electromagnetic field on as casting structure and surface quality of horizontal direct chill casting 7075 alloy

摘要

Horizontal direct chill (HDC) casting is a well established production route for aluminium alloy ingots; however, the ingots may suffer from inhomogeneous microstructures and serious macrosegregation due to the unbalanced cooling condition and gravitational effect. The present study considers the HDC casting of 7075 aluminium alloy ingot under the influence of a low frequency electromagnetic field (LFEF). Temperature measurement is employed to analyse the effect of LFEF on the HDC casting process. Surface topography and structure observation are conducted to analyse the effect of LFEF on the surface and interior quality of the HDC ingot. The results show that the LFEF can effectively uniformalise the thermal distribution, flatten the sump shape, improve the ingot surface quality, promote a transition from columnar/feathery to equiaxed dendritic growth and has a distinct grain refining effect.