Abstract: 7075 aluminum alloy ingot with the diameter of 100 mm has been produced by horizontal direct chill casting in different casting speed. The effect of the casting speed on the ingot surface and subsurface layer was studied by surface observation and subsurface structure analysis. It was found that increasing the casting speed results in the adding of segregation knots in the ingot surface. The thickness of the dendrite microstructure layer in the subsurface reduces with increasing the casting speed. And the elements of Zn, Cu and Mg enrich in the coarse dendrite microstructure layer of the ingot.

Key words: Horizontal direct chill casting, Casting speed, 7075 aluminum alloy, Surface quality