Influence of microstructure and loading conditions on the dynamic tensile property of Ni-based single crystal superalloys

To enhance the evaluation and prediction for service performance of hot-end components in equipment under the dynamic loads, a comprehensive study was conducted on Ni-based single crystal superalloys with diverse microstructures. This study involved a series of split Hopkinson tensile bar (SHTB) tests and related scanning electron microscopy (SEM) characterization. The influences of various factors, including the volume fraction of precipitation particles, phase coarsening, loading angle and strain rate, etc., on the dynamic tensile properties of superalloys were systematically investigated. Moreover, the relationships between these factors and the fracture morphology of alloys were thoroughly discussed. The results indicated that the microstructural features and strain rate have significant effect on the dynamic tensile properties of alloys, leading to a complex anisotropic characteristic occur in their dynamic tensile behaviors after phase coarsening. In general, the yielding strength displays a positive relationship with the tensile strength. As the volume fraction of precipitation particles or the strain rate increases, the alloy specimen gradually exhibits brittle fracture characteristics, with an increase in strength and a decrease in elongation. Besides, phase coarsening derived from the aging treatment significantly weakens the strength of alloys while enhancing their elongation, i.e., the specimens progressively show mixed fracture characteristics after phase coarsening, and both yielding strength and tensile ultimate strength gradually decrease while the elongation increases with the degree of phase coarsening. Furthermore, the strength and elongation of alloys at the loading angle of 55° are lower than those at the loading angle of 0°. Comparatively, for alloys with high volume fraction of precipitation particles and high degree of phase coarsening, the elongation achieves the maximum value at the loading angle of 55°. The corresponding variation characteristics are closely related to the fibrous zone and the cleavage plane on the fracture surface. Meanwhile, the variations in microstructure of materials and loading conditions affect the microcrack nucleation and fracture mode within the specimen, leading to various dynamic tensile properties in Ni-based single crystal superalloys. The present research and related results provide theoretical guidance and experimental data support for improving the mechanical performance of Ni-based single crystal superalloys and optimizing the design of hot-end components.