The strain field near the γ/γ′ interface in Ni-Al binary model single crystal superalloy

Abstract

The strain field near the γ/γ′ interface has a significant influence on the morphology evolution and the mechanical properties of Ni-based single crystal superalloys. The present work precisely determines the strain field near the γ/γ′ interface in a Ni-Al binary model single crystal superalloy by a combined usage of convergent beam electron diffraction (CBED) and high-resolution transmission electron microscopy (HRTEM) method. At positions slightly away from the γ/γ′ interface, the variation of lattice is sensitively measured by using standard CBED method. Within the range of about 10 nm close to the γ/γ′ interface, which is difficult to obtain a clear HOLZ pattern through traditional CBED solely, by using the CBED-calibrated HRTEM results, the complete lattice distortion and strain field are obtained. There is compressive strain in the γ′ phase and tensile strain in the γ phase, and the lattice strain affects a range as long as 80 nm near γ/γ′ interface. The strain distribution in the two phases is asymmetric, with the strain field in the γ phase obviously larger than in the γ′ phase. Our results provide important fundamental data for understands on the relationship between microstructure evolution and properties of Ni-based single crystal superalloys.