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

A serious SHTB tests and related SEM characterization were conducted regarding to Ni-based single crystal superalloys with various microstructures, and the influences different factors, including volume fraction of precipitation particles, phase coarsening, loading angle and loading rate, etc., on the dynamic tensile properties of superalloys were investigated systematically, then the relationships between these factors and fracture morphology of alloys were explored in detail. The results indicated that the microstructure features and loading rate have significant effect on the dynamic tensile properties of Ni-based single crystal superalloys, and complex anisotropic characteristics occur in the dynamic tensile properties after phase coarsening. In general, the yielding strength displays a positive relationship with the tensile strength. Along with the volume fraction of precipitation particles or the loading rate increases, the alloy specimen gradually exhibits a brittle fracture characteristic, with an increase in strength and a decrease in elongation. Besides, phase coarsening derived from aging treatment significantly weakens the strength of alloys while enhances their elongation, i.e., the specimens progressively show mixed fracture characteristics after phase coarsening, and both the yielding strength and the tensile strength gradually decrease while the elongation increases along with the degree of phase coarsening. Furthermore, the strength and the elongation of alloys usually decrease along with the increase of loading angle, however, for the alloys with high volume fraction of precipitation particle and high degree of phase coarsening, the elongation gradually increases along with the loading angle in the condition of high loading rate, achieving maximum value at the loading angle of 55°. The corresponding variation characteristics are firmly related to the fibrous zone and the cleavage plane on the fracture surface; meanwhile, the variations in material microstructure and loading conditions will 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 can provide theoretical guidance and data support for improving the mechanical performance of Ni-based single crystal superalloys and optimizing the structure of hot-end components.