Abstract
The effects of grain boundary misorientation angle (θ) on mechanical properties and the mechanism of plastic deformation of the Ni/Ni3Al interface under tensile loading were investigated using molecular dynamics simulations. The results show that the space lattice arrangement at the interface is dependent on grain boundary misorientations, while the interfacial energy is dependent on the arrangement. The interfacial energy varies in a W pattern as the grain boundary misorientation increases from 0° to 90°. Specifically, the interfacial energy first decreases and then increases in both segments of 0–60° and 60–90°. The yield strength, elastic modulus, and mean flow stress decrease as the interfacial energy increases. The mechanism of plastic deformation varies as the grain boundary misorientation angle (θ) increases from 0° to 90°. When θ = 0°, the microscopic plastic deformation mechanisms of the Ni and Ni3Al layers are both dominated by stacking faults induced by Shockley dislocations. When θ = 30°, 60°, and 80°, the mechanisms of plastic deformation of the Ni and Ni3Al layers are the decomposition of stacking faults into twin grain boundaries caused by extended dislocations and the proliferation of stacking faults, respectively. When θ = 90°, the mechanisms of plastic deformation of both the Ni and Ni3Al layers are dominated by twinning area growth resulting from extended dislocations.
Highlights
Ni-based single-crystal superalloys exhibit excellent high-temperature creep strength, fatigue resistance, oxidation resistance, and thermal corrosion resistance due to their special two-phase microstructure, and are commonly used in the manufacturing of aero-engine turbine blades and other key components [1,2]
The reason is that the crystal orientations of the Ni and Ni3 Al layers are different, the models with the same misorientation have the same arrangement of space lattice in the case of α > 0 and α < 0
The proliferation of stacking faults in the Ni3 Al layer and the decomposition of stacking faults caused by extended dislocation in the Ni layer still dominate the plastic deformation of the model with α = 80◦
Summary
Ni-based single-crystal superalloys exhibit excellent high-temperature creep strength, fatigue resistance, oxidation resistance, and thermal corrosion resistance due to their special two-phase microstructure, and are commonly used in the manufacturing of aero-engine turbine blades and other key components [1,2]. During the casting process of Ni-based superalloy blades, the large and low-angle grain boundaries caused by the differences in grain orientations can lead to scrapped castings. The difference in misorientation changes the free energy of the grain surface and the crystal microstructure [3], which results in the differences in mechanical properties and the scrapping of the castings. It is necessary to carry out in-depth research on misorientation. Many scholars have carried out research on misorientation through experiments. Zhao et al [4], Shi et al [5], and Huang et al [6] have studied the effects of misorientation on the tensile properties, Materials 2020, 13, 5715; doi:10.3390/ma13245715 www.mdpi.com/journal/materials
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