GH720Li时效态合金γ′相的微观形态和三维EBSD表征

Microstructure and three-dimension EBSD characterization of γ′ phases in aged GH720Li alloy

摘要:

GH720Li合金是航空发动机涡轮盘首选材料。采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、能谱仪(EDS)对GH720Li双时效态合金中三种γ′相的微观形貌、结构和微区成分进行了研究。基于聚焦离子束-电子束双束系统并应用EBSD-EDS联用技术对合金γ相和一次γ′相进行了分析，并应用Avizo软件对一次γ′相进行了三维重构。获得了合金一次γ′相的三维形态以及形态参数，给出了一次γ′相的体积分数，并与二维切片的分析结果进行了对比。结果表明，合金基体相和一次γ′相都存在大量的Σ3孪晶界。一次γ′相在三维尺度上存在多种形态，一些较大尺寸γ′相在二维截面上呈现不连续分布。三维EBSD可更全面反映一次γ′相的真实形态。一次γ′相三维信息的获得为改进合金的热处理工艺提供了依据。

Abstract:

GH720Li alloy is the preferred material for aero-engine turbine disk. The morphology, microstructure and micro-area composition of three kinds of γ′ in GH720Li dual-aged alloy were investigated via combination of scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive spectroscope (EDS). γ phases and primary γ′ phases were analyzed by EBSD-EDS method based on the focused ion beam/ electron microscopic system. 3D reconstruction of primary γ′ phases was done by Avizo software. The shapes, morphometric parameters and volume fraction of primary γ′ phases were given by the software and compared with the analysis results of 2D slice. The results show that there are a large number of Σ3 twin boundaries in both γ phases and primary γ′ phases. The primary γ′ phases have multiple shapes from a three-dimensional perspective. The larger continuous primary γ′ phases in three-dimensional space present discontinuous distribution in 2D slice sometimes. The real morphology of primary γ′ phases can be represented comprehensively by 3D EBSD method instead of 2D method. 3D information of primary γ′ provides the basis for heat treatment’s improvement of GH720Li alloy.