The solid-liquid (S/L) interfacial morphology of a single crystal superalloy DD8 has been investigated. The evolutionary behavior of cellular morphology with tilted preferred crystallographic orientation near cell-de...The solid-liquid (S/L) interfacial morphology of a single crystal superalloy DD8 has been investigated. The evolutionary behavior of cellular morphology with tilted preferred crystallographic orientation near cell-dendrite transition was dynamically observed, and the effect of crystallographic orientation on primary dendritic arm spacing has been examined. The experimental results show that for planar and cellular morphology, no any S/L interfacial anisotropy exists, but near cell-dendrite transition, the S/L interfacial anisotropy appears and gives rise to the cellular crystal fingers tilted from thermal flow direction to preferred crystallographic orientation. The crystal fingers with their preferred orientation parallel to DS growth direction are more stable than that with tilted orientation. For the tilted fingers, the surface on the side facing DS growth direction is less stable than that on the reverse side,the different stability on the two sides will lead to forming unsymmetrical dendritic microstructure. With this increase of tilted angle of preferred crystallographic orientation, the primary dendrite arm spacing decreases. (Edited author abstract) 7 Refs.展开更多
文摘The solid-liquid (S/L) interfacial morphology of a single crystal superalloy DD8 has been investigated. The evolutionary behavior of cellular morphology with tilted preferred crystallographic orientation near cell-dendrite transition was dynamically observed, and the effect of crystallographic orientation on primary dendritic arm spacing has been examined. The experimental results show that for planar and cellular morphology, no any S/L interfacial anisotropy exists, but near cell-dendrite transition, the S/L interfacial anisotropy appears and gives rise to the cellular crystal fingers tilted from thermal flow direction to preferred crystallographic orientation. The crystal fingers with their preferred orientation parallel to DS growth direction are more stable than that with tilted orientation. For the tilted fingers, the surface on the side facing DS growth direction is less stable than that on the reverse side,the different stability on the two sides will lead to forming unsymmetrical dendritic microstructure. With this increase of tilted angle of preferred crystallographic orientation, the primary dendrite arm spacing decreases. (Edited author abstract) 7 Refs.
