Unidirectional solidified Al-Fe alloy wires, 6 mm in diameter, were produced by Ohno Continuous Casting (OCC). The alloy composition used was 0.7 to 3.0% Fe and the casting speeds were 0.83 to 8.3 mm/s. The effect of the cooling rates on the solidification structures of the Al-Fe alloy OCC wires was studied. The cooling rate of the cast wires increased proportionally with the casting speed. In all the Al- (0.7 to 1.6%) Fe hypoeutectic alloy wires, the cast structures consisted of unidirectional solidified α-aluminum dendrites and eutectic structures. In the Al-1.9%Fe hypereutectic alloy wires, the cast structures were similar with primary crystals of hypoeutectic compositions. However, in the Al-3.0%Fe hypereutectic alloy wires cooled at the low rate of 4.62K/s, the cast structures consisted of unidirectional solidified eutectic cells. At cooling rates above 44.4K/s, the cast structures exhibited α-aluminum dendrites and eutectic structures. In the Al-1.9, 3.0%Fe hypereutectic alloys, primary intermetallic compounds (primary crystals of hypereutectic composition) were not observed. The shape of the solid-liquid interface of the wires was almost perpendicular to the casting direction.

  Vertical-type high-speed twin-roll casting can continuously produce aluminum alloy strips, and have excellent cooling capacity and high productivity. Al-Mg alloy is a typical non-heat treatment type aluminum alloy, and its main strengthening mechanism is solid solution strengthening by magnesium. Periodic patterns consisting of shiny region and un-shiny region with cracks are observed in the casting direction on the surface of the AC7A aluminum alloy fabricated by this method. Deterioration of surface quality, that is, increase in un-shiny region, is anticipated when magnesium content is increased for higher solid solution strengthening effect. In this study, Al-Mg alloy strips with magnesium content varied from 1 % to 12 % was fabricated, and the effect of magnesium composition on the periodic patterns was investigated. On the surface of the strips with the magnesium content of 2 % or more, periodic patterns were observed. As the magnesium content increased, the contrast of the patterns became clear. Magnesium segregation along the grain boundaries was observed in the vicinity of the strip surface in the un-shiny region. That residual liquid in the inter-dendrites and grain boundaries is thought to have been squeezed out to the surface by the solidification shrinkage at the region with locally lowered cooling rate. This resulted in the un-shiny region. The amount of magnesium squeezed out to the surface also increased with the increase in the magnesium content, resulting in, the contrast of the patterns became clear. The spacing of periodic patterns decreased with increasing magnesium content. Since the viscosity of the molten alloy decreases as the magnesium content increases, the vibration of the molten metal meniscus in the vicinity of the nozzle tip may occur more easily. This may be why the spacing of periodic patterns becomes small.

  The evaluation parameter of skin formation-type solidification tendency based on the numerical simulation of plate castings for alloys and pure metals was developed, and its applicability and influential factors were investigated. The skin formation index S/T (S : skin formation range, T : plate thickness, 0≤S/T<1) was defined based on the solidification time distribution of the castings, where S/T ≳ 0.8 for steel or pure metal and/or metal mold, and S/T ＝ 0 for aluminum or copper alloy and sand mold. The higher the mold temperature and/or superheat, or the greater the interfacial heat resistance between the casting and mold, the smaller was S/T. These S/T values were also consistent with conventional dimensionless numbers capable of partly evaluating the skin formation-type solidification tendency, thus confirming the applicability of S/T as the unified evaluation parameter. For alloys under ΔT*>0.01 (ΔT* : dimensionless solidification temperature range), the casting surface temperature was the dominant factor influencing S/T. On the other hand, for alloys under ΔT* <0.01 or pure metals, ΔT* significantly affected S/T despite the surface temperature, where S/T ≳ 0.7. Use of S/T enables the evaluation of behavior not reflected in the dimensionless numbers. In addition, the combined use of S/T with end or riser effects allows the evaluation of solidification characteristics.

  The effects of melting conditions on the chill formation of spheroidal graphite iron cast into metal mold were investigated. The influence of melting conditions on chill formation became apparent at 1400 ℃ or lower at which the reaction of magnesium contained in the spheroidizing additives during the spheroidizing treatment became mild. Chill formation tendency was changed by the melting conditions of the parent iron alloy used for sample melting, melting temperature and atmosphere and addition of iron oxide at the time of sample preparation. All chills in this experiment were reverse chill. Chill formation was suppressed by setting the amount of oxygen of the base molton iron before the spheroidizing treatment to 20 to 30 ppm, and even when the amount of oxygen of the base molten iron was too high or too low, chill was generated.