喷射沉积过程中显微组织的形成机制

通过对沉积还纵剖面的组织分析，发现沉积坯在进缘、上下表面及中心部位的显微组织明显不同。边缘及上下表面区试样的退火试验研究表明，细小的枝晶碎块在高温退火过程中发生凝共和粗化，并导致近球状晶粒组织的形成。试验确定其生长服从：D2-D02=6.37×1020e(-70036.1/T)·τ，晶界迁移激活能Qg=582KJ／mol。并依赖于两种机制：（1）在喷射沉积过程中无强烈变形枝晶的均匀化；（2）变形及断裂枝晶的生长和粗化。

MICROSTRUCTURE EVOLUTION MECHANISM DURING THE SPRAY DEPOSITION OF IC6 SUPERALLOY

By analyzing the microstructure along the longitudinal section of deposited preform, it is observed that there are evidently different microstructures among the periphery part, near top/bottom surface and the central part of the pre form. Annealing of the specimen taken from the periphery part and near top/bottom surface of the deposited pre form, revealed that fine dendrite fragments merge and coarse to lead to form near spheric grains. According to the experiment, its growth obeys the following function as:and the activated energy of boundary migration is equal to 582KJ/mol. The formation of non-dendrite spheric grain structure is finally completed in the process of high temperature annealing and relies on two mechanisms: (1) the homogenization of dendrites which did not experience severe de formation during spray atomization codeposition; (2) growth and coarsing of the deformed and fractured dendrite.