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利用垂直Bridgman法结合液态金属冷却法在恒定的液相温度梯度,凝固速率由2μm/s到490μm/s之间对Al-40%Cu合金进行定向凝固实验,凝固速率由5μm/s到100μm/s之间对Ni-11%NbC合金定向凝固。结果表明:Al-38%Cu合金定向凝固下的组织为耦合的片层共晶和少量的领先相的混合结构,随着凝固速率的逐步提高,共晶界面形态由平界面向胞界面转化,且领先相为非小晶面方式生长。Ni-11%NbC合金定向凝固下的组织为全耦合生长的棒状共晶,当凝固速率有一定幅度的提高时,平界面将会失稳。且初生相为典型的小平面生长方式。采用成分过冷理论计算这两种合金系的临界平界面速度,理论和实验较为符合。
The vertical Bridgman method and the liquid metal cooling method were used to conduct the directional solidification experiment of Al-40% Cu alloy at a constant liquidus temperature gradient and solidification rate from 2μm / s to 490μm / s. The solidification rate was from 5μm / s to 100μm / s between the directional solidification of Ni-11% NbC alloy. The results show that the microstructure of Al-38% Cu alloy is a combination of lamellar eutectic and a few leading phases. With the increase of solidification rate, the morphology of eutectic interface transforms from the flat interface to the cell interface, And the leading phase for non-small crystal face growth. The microstructure of the Ni-11% NbC alloy under directional solidification is a rod-shaped eutectic with fully coupled growth. When the solidification rate increases to a certain extent, the flat interface will be unstable. The primary phase is a typical facet growth mode. Using the theory of subcooling of components, the critical plane velocity of these two alloys is calculated, which is in good agreement with the theory and experiment.