Effects of grain boundary- and triple junction-character on intergranular fatigue crack nucleation in polycrystalline aluminum

Kobayashi, Shoichi; Inomata, Toshiyuki; Kobayashi, Hiroyuki; Tsurekawa, Sadahiro; Watanabe, Tadao

doi:10.1007/s10853-007-2236-z

Cited by 88 publications

(35 citation statements)

References 24 publications

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“…Note that such a trend is the same as that observed for unalloyed pure Al [27][28][29][30] or 6061 with higher Si content [2]. In contrast, the curve of the new alloy shows clear discontinuity; N f significantly increases at  a between 90…”

Section: S-n Behavior Analysissupporting

confidence: 69%

Effect of additional magnesium on mechanical and high-cycle fatigue properties of 6061-T6 alloy

Takahashi¹,

Shikama²,

Nakamichi³

et al. 2015

Materials Science and Engineering: A

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Abstract:The effect of additional solute magnesium (Mg) on mechanical and high-cycle-fatigue properties of 6061-T6 aluminum alloy is investigated in detail. By adding 0.5% and 0.8% Mg to the 6061-T6 alloy with a normal stoichiometric Mg 2 Si composition (base alloy), the alloy exhibits eminent strain-aging characteristics demonstrated by the emergence of serrated flow, the negative 2 strain-rate-sensitivity and relatively weakened temperature dependency of flow stress. The Mg-added new alloy also shows higher work-hardening rate than the base alloy particularly at initial flow regime and at lower strain rate. The S-N curve of the new alloy shows a clear fatigue limit which is absent in the base alloy. The fatigue limit of the new alloy is shown to be controlled by the threshold against small crack growth. Moreover, the new alloy clearly exhibits a coaxing phenomenon (time-dependent strengthening) which is absent in the base alloy. The coaxing effect is attributed to the existence of a small quasi-non-propagating crack whose growth resistance gradually increases during stress amplitude step-ups.

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Section: S-n Behavior Analysissupporting

confidence: 69%

Effect of additional magnesium on mechanical and high-cycle fatigue properties of 6061-T6 alloy

Takahashi¹,

Shikama²,

Nakamichi³

et al. 2015

Materials Science and Engineering: A

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“…Concerning the interaction between dislocations and grain boundaries during the cyclic test, detailed studies on Cu polycrystal, 17,23) Cu bicrystal 24) and Al polycrystal 25) were carried out taking into account the grain boundary characteristics. Winter et al.…”

Section: Fig 14 Tem Micrographs Of Ti-if3mentioning

confidence: 99%

“…2) Low dislocation-density regions were found along all of the adjacent initial grain boundaries with a distance of ap-proximately 0.5 mm in the Si-bearing steels. Concerning the interaction between dislocations and grain boundaries during the cyclic test, detailed studies on Cu polycrystal, 17,23) Cu bicrystal 24) and Al polycrystal 25) were carried out taking into account the grain boundary characteristics. Winter et al 17) and Luoh et al 23) reported that dislocation free zones (DFZ) along grain boundaries were formed when the vein structures developed within grains, whereas DFZ were not formed in the case of cell structures, which is very similar to the results of the present study using Fe-Si alloy.…”

Section: Evolution Of Dislocation Structure During Fatiguementioning

confidence: 99%

Evolution of Dislocation Structure and Fatigue Crack Behavior in Fe–Si Alloys during Cyclic Bending Test

et al. 2009

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Fig. 14. TEM micrographs of Ti-IF3(1 % Si) tested under a high stress amplitude showing development of the periodically arranged dislocation wall structure near the top surface (sϭ380.9 MPa, Nϭ8 500).proximately 0.5 mm in the Si-bearing steels. Concerning the interaction between dislocations and grain boundaries during the cyclic test, detailed studies on Cu polycrystal, 17,23) Cu bicrystal 24) and Al polycrystal 25) were carried out taking into account the grain boundary characteristics. Winter et al. 17) and Luoh et al. 23) reported that dislocation free zones (DFZ) along grain boundaries were formed when the vein structures developed within grains, whereas DFZ were not formed in the case of cell structures, which is very similar to the results of the present study using Fe-Si alloy. Although further study is required, Luoh et al. 23) concluded that the multipolar dislocation loop patches (MLPs) and walls (MLWs) are built up due to grain boundary incompatible stresses providing secondary glides, which are thought to cause annihilation of dipole loops by intersecting MLPs or MLWs. Referring to this model, it is inferred that in the Si-bearing steels the difficulty of cross slip leads to the annihilation of dislocation dipole loops in the vicinity of grain boundaries by intersecting MLPs and MLWs, or dislocations simply sinks into grain boundaries. In the case of pure iron after the deformation of cold rolling, localized softening near the initial grain boundaries has been reported. 26)Further systematic quantitative study in bcc metals is necessary to clearly understand the mechanism.The present study shows that the saturated dislocation structure varies with the cyclic stress amplitude. As shown in Fig. 17, the cell width and vein width varied with the ISIJ International, Vol. 49 (2009) stress amplitude, respectively. More specifically, the cell width remained comparatively large, although varying from approximately 5 to 8 mm under low to middle-stress amplitude, and clear cell structures developed under high-stress amplitude with comparatively homogenous and fine cell sizes of 2 to 3 mm. On the other hand, the vein width varied largely under low-stress amplitude, bundled dislocations started to appear under middle-stress amplitude, and the vein width converged to 0.5 to 1 mm dimension homogeneously with further increasing stress amplitude with a channel width of about 0.5 mm. The relationship between the development of dislocation structures and stress amplitude during cyclic deformation has already been investigated from both experimental and theoretical points of view mainly on Cu. 27,28) The cyclic stress (t) of materials with periodically arranged dislocation walls is expressed by the sum of the stress necessary for dislocation to bow out into the channel (t bowing ) and interaction stress (t dip ) of screw dislocation dipoles within the channel. t bowing is expressed by Gb/d c andt dip is by Gb/4ph, where G, b, d c and h are shear modulus, Burgers vector, channel width and interval of slip plane...

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“…The GBCD and its mechanistic origin are of interest because the grain boundary network can affect bulk properties such as the mechanical response, transport kinetics or corrosion resistance [21,[26][27][28][29][30][31][32][33][34][35][36][37]. This point is exemplified by the widespread interest in grain boundary engineering [26][27][28][29]31,[34][35][36][37][38][39][40][41][42][43]. Although the GBCD is thought to be a sensitive indicator of materials properties and that it is possible to engineer a polycrystal by controlling the GBCD, little is known about the mechanism of how anisotropic distributions develop.…”

Section: Introductionmentioning

confidence: 99%

Mechanism for the development of anisotropic grain boundary character distributions during normal grain growth

Dillon

Rohrer

2009

Acta Materialia

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Grain boundaries in polycrystalline magnesia-doped alumina and yttrium aluminum garnet were classified as growing in area or shrinking in area on the basis of topology and curvature considerations. Measurements of dihedral angles at grain boundary thermal grooves were used to determine that the energies of the growing boundaries are, on average, lower than the energies of the shrinking boundaries. The observations also show that the length of a boundary is inversely correlated to its energy. The findings suggest that anisotropic grain boundary character distributions, which influence the properties of polycrystals, develop because higher-energy grain boundaries are preferentially eliminated from the network during grain growth.

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Effects of grain boundary- and triple junction-character on intergranular fatigue crack nucleation in polycrystalline aluminum

Cited by 88 publications

References 24 publications

Effect of additional magnesium on mechanical and high-cycle fatigue properties of 6061-T6 alloy

Effect of additional magnesium on mechanical and high-cycle fatigue properties of 6061-T6 alloy

Evolution of Dislocation Structure and Fatigue Crack Behavior in Fe–Si Alloys during Cyclic Bending Test

Mechanism for the development of anisotropic grain boundary character distributions during normal grain growth

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