In-situ EBSD study of deformation behavior of nickel-based superalloys during uniaxial tensile tests

Abstract

In this paper, we study the deformation behavior of nickel-based superalloys by in-situ EBSD and uniaxial tensile tests. This study mainly focuses on the microstructure evolution in the same area of the sample during deformation, including the evolution of various types of grain boundaries, geometrically necessary dislocations, grain orientations and texture, and their effect on the mechanical properties. The results show that the rotation of grains is closely related to their initial orientation during deformation. The lattice of grain is rotated to a certain extent to accommodate the more favorable orientation under low strain, leading to higher Schmid factors for the sample. Under large stresses, the grains occur deformation, multiple slip systems start simultaneously or alternately and the Schmid factors value gradually tends to stabilize at a lower level. Meanwhile, the texture orientation density of the initial Rotating cubic {001} < 110 > texture, α-fiber (RD//<110 >) texture, and γ-fiber (ND // <111 >) gradually decrease or even disappears, while the texture orientation density of Copper {112} < 111 > and Goss {011} < 100 > increases during uniaxial tensile deformation for Cr20Ni80 alloy. Grain rotation may be a result of large strain due to stress triaxiality and resulting plane stress condition owing to specimen dimension, which is beneficial to improve the plastic deformability of the alloy. Interestingly, with the increase of strain, the average misorientation angle first decreases and then increases, which is associated with the dislocation density. In addition, serious torsion occurs in the grains during this process, forming a large number of substructures. These substructures result in grain refinement and the Hall-Petch effect. In fact, during the deformation process, multiple strengthening mechanisms act in coordination, leading to an increase in the strength of the alloy.