Abstract
As material for key parts applied in the aerospace field, the Cu-Be-Co-Ni alloy sustains cyclic plastic deformation in service, resulting in the low cycle fatigue (LCF) failure. The LCF behaviors are closely related to the precipitation states of the alloy, but the specific relevance is still unknown. To provide reasonable regulation of the LCF properties for various service conditions, the effect of precipitation states on the LCF behaviors of the alloy was investigated. It is found that the alloy composed fully of non-shearable γ′ precipitates has higher fatigue crack initiation resistance, resulting in a longer fatigue life under LCF process with low total strain amplitude. The alloy with fine shearable γ′I precipitates presents higher fatigue crack propagation resistance, leading to a longer fatigue life under LCF process with high total strain amplitude. The cyclic stress response behavior of the alloy depends on the competition between the kinematic hardening and isotropic softening. The fine shearable γ′I precipitates retard the decrease of effective stress during cyclic loading, causing cyclic hardening of the alloy. The present work would help to design reasonable precipitation states of the alloy for various cyclic loading conditions to guarantee its safety in service.
Highlights
The Cu-Be-Co-Ni alloy possesses a strength similar to ultra high strength steel and superior elastic properties benefited from the significant precipitation strengthening effect [1]
Could be be observed in in thethecorresponding (SADP), The could observed correspondingselected selectedarea areadiffraction diffraction pattern pattern (SADP), which was considered as the sign of a change in habit planes from the former metastable phase which was considered as the sign of a change in habit planes from the former metastable phase [21]
The cyclic hardening and cyclic softening behaviors of the alloy were well explained by the evolution of effective stress and internal stress during the low cycle fatigue (LCF) process
Summary
The Cu-Be-Co-Ni alloy possesses a strength similar to ultra high strength steel and superior elastic properties benefited from the significant precipitation strengthening effect [1]. It possesses high fatigue strength, thermal conductivity and wear resistance [2]. Owing to these remarkable properties, Cu-Be-Co-Ni alloy is widely applied in the mechanical components of aviation, aerospace, military industry and other fields, such as the axle sleeves and pivots on the landing gear of large aircraft [3]. The LCF behaviors, especially the cyclic hardening and softening behaviors, of the Cu-Be-Co-Ni alloy need to be further investigated for the safety and reliability requirements
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