Effect of Temperature on the Low-Cycle Fatigue Characteristics of Single Crystals Made of an Ni₃Al-Based Rhenium-Containing Intermetallic Alloy

Abstract—The low-cycle fatigue (LCF) of the single crystals made of a γ'-Ni₃Al-based VKNA-25 γ' + γ nickel superalloy is studied at 10⁴ cycles and a temperature of 20, 750, and 900°C. A temperature anomaly in the LCF fatigue limit of the VKNA alloy, namely, its increase with temperature in the range from 20 to 750°C, is detected. This anomaly is related to a change from octahedral to cubic slip at the temperature of the peak in L1₂-ordered alloys and to a change in the properties of the γ' and γ phases. At normal temperature, the static tensile strength and the LCF characteristics of the [111] single crystals are higher than those of the single crystals with other crystallographic orientations (CGOs). The static tensile strengths of the [001] and [111] single crystals at 900°C and the strengths of the single crystals with all CGOs at 1000°C are almost the same, and the LCF fatigue limit of the [001] single crystals at 900°C is slightly higher than that of the [111] single crystals.