Tuning Low Cycle Fatigue Properties of Cu-Be-Co-Ni Alloy by Precipitation Design

Abstract

As material for key parts applied in the aerospace field, the CuBe 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.

Multicomponent intermetallic nanoparticles and superb mechanical behaviors of complex alloys

“…The intensive polyslips of dislocations are helpful for relieving the stress concentration on the {111} primary slip planes. Meanwhile, the progressive accumulation of these in-directional dislocations and their mutual interactions produced a pronounced forest dislocation hardening, i.e., the short-range effective stress hardening (29)(30)(31)(32). We conducted tensile load-unload-reload tests to further quantify the dynamic evolutions of the work-hardening responses and associated flow stress partitioning behaviors (fig.…”

Effects of Cold Rolling and Aging Treatment on the Properties of Cu-Be Alloy

“…Aging after quenching from solution treatment remarkably hardens the alloy [1][2][3][4]. The precipitation sequence in this alloy has been extensively studied and can be summarized as follows [5][6][7][8]: α supersaturated solid-solution→G.P zones →γ΄΄→γ΄→γ (Cu-Be). The G.P zones are monolayer plates that form coherently on {100} matrix and revealed as streaks along 200 〈 〉 α directions, γ΄΄ is a metastable phase with a monoclinic structure appearing as intensity maxima in the streaks along the 200 〈 〉 α directions with aging treatment [9][10][11][12][13].…”