2019 Volume 4 Pages 109-114
Solidification structures and casting soundness of multilayer Al-Si alloy pipes produced by a two-step centrifugal casting process have been investigated. Two kinds of molten metals, i.e., the first melt (Al-12mass%Si or Al-14mass%Si alloy) and the second melt (Al-32mass%Si-0.1mass%P alloy) having a higher liquidus temperature were cast in sequence into a vertical centrifugal caster. The second melt was cast after the solidified shell of the first melt had grown partway from the contact surface with the mold. The cast pipe specimens were typically composed of three layers. The outer layer was the surviving part of the solidified shell of the first melt after contact with the second melt cast at a high temperature. The intermediate layer was derived from the molten or partially-molten part of the first melt. The inner layer had a hypereutectic structure containing fine primary silicon crystals originated in the second melt. The integrated length of crack-like defects at the boundary between the intermediate and inner layers varied depending on the growth degree and structure of the solidified shell of the first melt.
