籽晶成分对单晶高温合金定向凝固起始界面形态和取向的影响

Effect of Seed Compositions on the Morphology of Initial Interface and Crystal Orientation during the Directional Solidification of Single Crystal Superalloy

研究了纯Ni、Ni-12%Cr和DD483合金分别作为籽晶定向生长镍基单晶高温合金的凝固过程。结果表明,纯Ni和Ni-12%Cr籽晶的凝固界面历经平界面—胞状界面—枝晶界面的转变过程,采用树枝晶的DD483籽晶时,凝固界面直接由籽晶重熔区进入枝晶生长阶段。单晶高温合金的晶体取向延续了籽晶的晶体取向,但纯Ni籽晶/高温合金界面处的晶体取向发生小角度偏转。分析认为,这是由于成分突变引起γ相的晶格常数发生变化所造成的。

Directional solidification of single crystal superalloy by using seeds of pure Ni, Ni- 12% Cr and DD483 alloys were investigated, respectively. The experimental results showed that the solid/liquid interface changed from planar to cellular, and then to dendrite during the directional solidification process by using the pure Ni and Ni-12% Cr seeds, separately. When the DD483 alloy seed was used, the solidification interface transformed from seed melt-back zone into dendrite directly. The single crystal castings kept the orientation of bottom seeds in the dendrite growth stage. There was a small angle deviation from the seed orientation near pure Ni seed/DD483 superalloy interface. This may be due to the change of lattice constant of γ phase caused by compositions variation.