超高温度梯度下凝固速率对一种镍基单晶高温合金定向凝固组织的影响

Directional Solidification of a Ni-Based Single Crystal Superalloy under High Temperature Gradient

摘要:

采用区域熔炼液态金属冷却超高温度梯度定向凝固法 (ZMLMC)，研究凝固速率对一种镍基高温合金微观组织的影响。结果显示：在温度梯度基本不变的条件下，随着凝固速率的提高，枝晶结构逐渐细化，一次枝晶间距λ1与二次枝晶间距λ2减小，且λ1和λ2分别与V-1/4和V-1/2呈线性关系；γ'相尺寸随凝固速率的提高而减小，形貌逐渐趋向于立方状，而在同一速率下，枝晶干的γ'相形状相对较规则，接近立方形，枝晶间的γ'相则趋于无规，其尺寸也较枝晶干区域更为粗大；γ/γ'共晶尺寸随凝固速率的提高而减小，分布趋于弥散，但总的体积分数变化不大

Abstract:

The effects of solidification rate on the microstructure of a Ni-based superalloy were investigated by zoom melting liquid metal cooling (ZMLMC) unidirectional solidification. The temperature gradient was approximately constant. It is revealed that with the increase of solidification rate, the dendrite structure is refined, and both the primary dendrite spacing λ1 and the secondary dendrite spacing λ2 are reduced, they show a linear relationship with v-1/4 and v-1/2, respectively. The sizes of γ' precipitates decrease with increasing of solidification rate, and the shapes turn to be regular. At the same rate, the γ' phase in interdendrite area is larger and more irregular than that in dendrite area. The γ/γ' eutectic also becomes smaller and more dispersed with the increase of solidification rate, but the total volume proportion remains stable