单晶镍基合金拉伸蠕变期间γ′相定向粗化的特征及影响因素

Features and effect factors of directional coarsening for γ′ phase during creep of single crystal nickel base superalloys

对 [0 0 1 ]取向单晶镍基合金恒载拉伸蠕变的组织形貌进行 SEM观察和 EDAX成分分析 ,研究了 γ′相定向粗化特征及影响因素。结果表明 ,由于应力场和温度场的差别 ,蠕变样品不同位置处筏状 γ′相粗化尺寸及特征不同 ,近断口处筏状 γ′相扭曲且粗化加剧 ,随离断口距离增加 ,γ′相粗化程度减弱 ;在γ′相定向粗化的扩散场中 ,分配比值较小且相对稳定的元素 W可成为其他元素的扩散障碍 ,使合金 2中 γ′相的形筏时间明显延长。

The microstructures of [001] single crystal nickel base superalloys under the constant loading tensile creep were observed by means of SEM, and the chemical composition of γ and γ′ phases were analyzed by EDAX in order to investigate the features and effect factors of the directional coarsening of γ′ phase. Results showed that the various features display at different locations of the sample. Due to the difference of the stress and temperature fields, the γ′ rafts near the fracture surface possessed a twisted feature and coarsened remarkably, which became less pronounced with the increase of the distance far from the fracture. The element W of the higher concentration in alloy 2, having the smaller diffusivity and partitioning ratio between the γ′/γ phases, may obstruct the diffusion of the other elements in the diffusion field of γ′ phase directional coarsening, which reduced the γ′ rafting rate in alloy 2.