Exploring low cycle fatigue anisotropy and the failure mechanism of the DD412 single crystal alloy for aeroengines. (April 2023)

• Record Type: Journal Article
• Authors: Dou, Xuezheng; Jiang, Liwu; Song, Jinxia; Wang, Dinggang
• Is Part Of: International journal of fatigue. Volume 169(2023)
• Publication Date: 2023-04
• Subjects: Nickel-based single crystal superalloy -- Low cycle fatigue properties -- Anisotropy -- Crystal orientation -- Failure mechanism; Materials -- Fatigue -- Periodicals; Materials -- Fatigue; Periodicals; 620.1122
• DOI: 10.1016/j.ijfatigue.2022.107487
• Languages: English
• ISSNs: 0142-1123

Abstract

Highlights: The low cycle fatigue properties of DD412 alloy with different orientations have significant anisotropy at 760℃. The anisotropy of low cycle fatigue properties of DD412 alloy with different orientations at 760℃ is mainly related to the difference of elastic modulus. The dislocation configurations of DD412 alloy with different orientations after low cycle fatigue at 760℃ are different. Single crystal alloys DD412 with different orientations have different low cycle fatigue properties and fatigue damage mechanism. Abstract: In this paper, the low cycle fatigue properties of the DD412 single crystal alloy with [0 0 1], [0 1 1] and [1 1 1] orientation at 760℃ were studied. A correlation between low cycle fatigue properties and orientation was found, and the microstructure evolution and fatigue failure mechanism were studied, which lays a solid theoretical foundation for the engineering application of the DD412 single crystal alloy. The fatigue testing was uniaxial. The experimental results show that the low cycle fatigue properties of the DD412 alloy with different orientations have significant anisotropy at 760℃. The single crystal alloy with a [0 0 1] orientation parallel to the loading axis exhibited the longest fatigue life at high strains, and the alloy with [1 1 1] orientation exhibited the shortest fatigue life at high strains, while the alloy with [0 1 1] orientation was located between these two durations, which is mainly related to the difference of elastic modulus. For the alloy with [0 0 1] orientation, elastic deformation is the main fatigue damage mechanism, and cleavage-like fracture occurs along a specific crystallographic plane. For the alloy with [0 1 1] orientation, under high strain amplitude, the fatigue fracture is caused by the joint action of plastic deformation and elastic deformation, and cleavage tear mixed fracture occurs. For the alloy with [1 1 1] orientation, under high strain amplitude, plastic deformation is the main fatigue damage mechanism. The dislocation configurations of the DD412 alloy with different orientations after low cycle fatigue at 760℃ are different. The main observation in the alloy with [0 0 1] orientation is the dislocations cross-slip in the γ channel to form serrated dislocations; while in the alloy with [0 1 1] orientation, there are a large number of dislocations entangled in the γ channel; and in the alloy with [1 1 1] orientation, there are two high density parallel dislocation bands in the γ channel.