Al-Mg合金による鋳塊のチャンネル型偏析の生成に関する実験的研究

抄録

Effects of solidification condition and morphology of growing crystals on the formation of channel-type segregation were investigated by using unidirectionally solidified Al-Mg alloys, in which denstiy change in interdendritic liquid is similar to that in steel.
Under any casting condition, channels formed at any growth rates less than a critical value R^*=(2.0±0.2)×10⁻⁴ (m·s⁻¹). Channels were mainly generated from a mixed zone of branched columnar and equiaxed crystals near equiaxed sedimental zone, and did not form in a sedimental zone. In the vicinity of the boundary region, the distribution of dendrite crystals were not uniform, and larger liquid pools existed at an early stage of solidification. The channel-type segregation was considered to originate from the stronger fluid flow through the pools. The segregation took the form of channel at fraction of solid f_s=0.2-0.3.