Cyclic deformation and fracture of pure aluminium polycrystals

Videm, Marianne; Ryum, N.

doi:10.1016/s0921-5093(96)10262-8

Cited by 21 publications

(9 citation statements)

References 18 publications

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“…The observed cyclic stress response (csr-curve) in a typical test on a nonannealed sample is shown in Fig. 2; it is in close agreement with earlier experiments [45,46]. To associate different stages of cyclic behavior with dislocation patterning, we relied on: (i) scanning electron microscopy (SEM) observations of the surface of a sample during a test performed under the same loading conditions but interrupted at various stages of fatigue life; (ii) previously published TEM observations for pure aluminum samples subjected to similar loading protocols ( ε p between 0.48 and 0.64%) [45].…”

Section: Cyclic Deformation Stages and Dislocation Patternssupporting

confidence: 89%

Plastic intermittency during cyclic loading: From dislocation patterning to microcrack initiation

Weiss

Rhouma

Deschanel

et al. 2019

Phys. Rev. Materials

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In metallic materials subjected to cyclic loading, strain hardening as well as fatigue crack initiation have been linked for a long time with the evolution of dislocation patterns and structures. In particular, the development of low-energy dislocation configurations such as persistent slip bands (PSBs) is considered as a precursor to crack initiation. However, the associated scenarios have been elaborated mainly from postmortem observations capturing only static pictures of dislocation patterns, while the dynamics of the problem has been somewhat overlooked. Here we analyze collective dislocation dynamics during cycling loading of aluminum using acoustic emission (AE). A strong link is revealed between dislocation patterning, cyclic hardening/softening, and the intermittency of plasticity: Plastic intermittency and dislocation avalanches rapidly decay during the initial hardening stage, in conjunction with the reduction of an internal length scale characterizing the dislocation structure. However, in nonannealed samples, a transient softening stage ensues, associated with a brutal reorganization of this structure. These initial stages of cyclic deformation illustrate the competition between two phenomena: collective dislocation dynamics, governed by long-ranged elastic interactions among dislocations, and the emergence of a self-organizing network controlled by short-range interactions and progressively inhibiting collective effects. Later on, the emergence of PSBs is accompanied by a reincrease of the AE intermittent activity. We propose that the associated AE bursts may be the signature of collective and coordinated dislocation motions along PSBs leading to the formation of incipient microcracks.

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Section: Cyclic Deformation Stages and Dislocation Patternssupporting

confidence: 89%

Plastic intermittency during cyclic loading: From dislocation patterning to microcrack initiation

Weiss

Rhouma

Deschanel

et al. 2019

Phys. Rev. Materials

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“…According to the current investigations, the formation of the twist will contribute to the occurrence of secondary cyclic hardening in fatigued Al single crystals, leading to the obvious fluctuation of a cyclic hardening curve (see Figure 3(d)). Videm and Ryum [15,16] observed the similar slip morphologies in ½001 Al single crystals at low strain amplitudes and referred to them as the cord-like structures. As shown in Figures 3(b), (d), and (f), cord-like structures are one of the classic morphologies in fatigued Al single crystals.…”

Section: Resultsmentioning

confidence: 87%

“…Based on plenty of previous results and the current research, the cell structure is seen most commonly in Al single crystals with various orientations, including single-slip orientations ½ " 123, ½ " 125, and ½ " 579 [9,10,12,20,21,24,25] ; double-slip orientations ½ " 112, ½ " 114, and ½ " 1120 [26] ; and even multiple-slip orientations ½001 and ½011. [15][16][17] In other words, whether the cell forms is not dominated by the orientation of Al single crystals but is determined by the characteristic of Al itself.…”

Section: Resultsmentioning

confidence: 99%

“…However, at 77 K (-196°C), Charsley and Harris [13] and Charsley et al [14] found that wall structures including PSB-ladder structures appeared in pure polycrystalline Al. Thereafter, Videm and Ryum [15,16] systematically summarized the cyclic deformation behavior of ½001 Al single crystals and compared it with the results of polycrystalline Al. They found that highly characteristic deformation patterns with a cord-like appearance at low strain amplitudes and a tweed-like appearance at higher strain amplitudes were developed.…”

Section: Introductionmentioning

confidence: 99%

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Cyclic Deformation Behaviors of $$ [\bar{5}79] $$-Oriented Al Single Crystals

Zhongguang

Zhang

2010

Metall Mater Trans A

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During the cyclic deformation of ½ " 579, Al single crystals with a high stacking fault energy produced slip bands that were characterized by wavy slip. Its cyclic stress response curve demonstrated that the specimen experienced hardening-softening-secondary hardening in sequence with repeated fluctuation stresses usually less than 10 MPa, which is far lower than those of Cu, Ni, and Ag single crystals. Finally, the whole surface of the Al single crystals was covered with intense intrusion and extrusion, and the cell structure is the most typical dislocation arrangement. These cells mainly comprise loose clusters of dislocations, which move more freely. In the center of the cell, the dislocation density is relatively low, and most dislocations concentrate in the cell wall. At room temperature, compared with cyclically deformed Cu, Ni, and Ag single crystals, the cyclic deformation behaviors of Al single crystals show significant differences, which are highlighted in this study.

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“…Influence of grain size and defect sizeBased on the experimental results, the influence of grain size and/or defect size on the HCF behavior of pure aluminium is firstly discussed.According to Figures 4 and 5, for both the small and large grain microstructures, the cyclic behavior is composed of three successive stages: primary hardening, softening and secondary hardening. This specific behavior, which is explained by the formation and evolution of dislocation structures[24,25,26,27], has already been highlighted by Giese et al[28] and Videm et al[29]. In the following, the plastic strain range, determined at the transition between the softening and secondary hardening stages, is arbitrarily chosen as a macroscopic plastic activity indicator for given grain size and stress amplitude.…”

mentioning

confidence: 76%

Experimental study of the impact of geometrical defects on the high cycle fatigue behavior of polycrystalline aluminium with different grain sizes

Bracquart

Mareau

Saintier

et al. 2018

International Journal of Fatigue

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Geometrical defects are known to have a detrimental influence on the high cycle fatigue resistance of metallic alloys, smaller defects being less harmful. In this experimental work, the influence of the defect size on the high cycle fatigue behavior of polycrystalline aluminium with different grain sizes is investigated, to better understand the role of internal length scales. Firstly, different thermomechanical treatments are applied to obtain aluminium samples with either small (100 µm) or large (1000 µm) grains. The samples are used for preparing fatigue specimens, with either small (100 µm) or large (1000 µm) hemispherical defects. Fully reversed stress-controlled fatigue tests are then carried out.

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Cyclic deformation and fracture of pure aluminium polycrystals

Cited by 21 publications

References 18 publications

Plastic intermittency during cyclic loading: From dislocation patterning to microcrack initiation

Plastic intermittency during cyclic loading: From dislocation patterning to microcrack initiation

Cyclic Deformation Behaviors of $$ [\bar{5}79] $$-Oriented Al Single Crystals

Experimental study of the impact of geometrical defects on the high cycle fatigue behavior of polycrystalline aluminium with different grain sizes

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