Effect of harmonic structure design with bimodal grain size distribution on near-threshold fatigue crack propagation in Ti–6Al–4V alloy

Kikuchi, Shoichi; Imai, Tetsuo; Kubozono, Hiroki; Nakai, Yoshikazu; Ota, Masaki; Ueno, Akira; Ameyama, Kei

doi:10.1016/j.ijfatigue.2016.02.038

Cited by 43 publications

(30 citation statements)

References 23 publications

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“…For example, Morita et al [9] reported that the strength of Ti-6Al-4V alloy was improved by a short-time duplex heat treatment without a reduction in ductility. In particular, we have developed a harmonic structure design [12][13][14][15][16][17][18][19], which consists of a coarse-grained structure surrounded by a network structure of fine grains, using a powder metallurgy to improve both the strength and ductility of commercially pure titanium and Ti-6Al-4V alloy.…”

Section: Introductionmentioning

confidence: 99%

“…In an attempt to achieve sufficient performance of titanium-based harmonic structured materials for practical applications in the engineering fields, we have examined the fatigue properties and the near-threshold fatigue crack propagation of Ti-6Al-4V alloy with harmonic structure [16,18,19]. It has been clarified that the crack path in Ti-6Al-4V alloy is influenced by the harmonic structure, which results in decreases of the threshold stress intensity range ∆Kth, effective threshold stress intensity range ∆Keff,th, and the closure stress intensity factor, Kcl.…”

Section: Introductionmentioning

confidence: 99%

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Effect of bimodal grain size distribution on fatigue properties of Ti-6Al-4V alloy with harmonic structure under four-point bending

Kikuchi

Hayami

Ishiguri

et al. 2017

Materials Science and Engineering: A

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Titanium alloy (Ti-6Al-4V) with a bimodal harmonic structure, which is defined as a coarse-grained structure surrounded by a network structure of fine grains, was fabricated using powder metallurgy to improve both the strength and ductility. The microstructure of the sintered compacts was characterized using electron backscattered diffraction (EBSD). The areal fraction of the fine-grained structure in the harmonic structure tended to increase with the milling time. Tensile tests and four-point bending fatigue tests at a stress ratio of 0.1 were performed in air at room temperature. The tensile strength, 0.2% proof stress and fatigue limit of Ti-6Al-4V alloy with harmonic structure tended to increase as the areal fraction of the fine-grained structure increased. In contrast, elongation decreased due to the formation of a high areal fraction of the fine-grained structure (79.0%), which resulted in a reduction of the fatigue life with a low cycle regime. Thus, titanium alloy with high strength, ductility and fatigue resistance can be formed by optimization of the milling conditions. Furthermore, the mechanism for fatigue fracture of the Ti-6Al-4V alloy with a harmonic structure is discussed with respect to fractography and crystallography. A fatigue crack was initiated from the α-facet of the coarse-grained structure in the harmonic structure.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of bimodal grain size distribution on fatigue properties of Ti-6Al-4V alloy with harmonic structure under four-point bending

Kikuchi

Hayami

Ishiguri

et al. 2017

Materials Science and Engineering: A

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“…Stress intensity range K, MPam 1/2 Crack growth rate da/dN, m/cycle K eff for long crack (Fig.6(a) structure at near-threshold levels is attributable not to crack closure but to grain size, i.e., the effect of slip-band growth resistance by grain boundaries and misorientations [37,38]. This same effect, in which a bimodal harmonic structure affects Keff,th, has also been observed for a Ti-6Al-4V alloy [29].…”

Section: -7mentioning

confidence: 53%

“…K-decreasing tests were also conducted to approach the fatigue threshold. The present study employed disk-shaped compact (DC(T)) specimens (2 mm thick) [28][29][30] in accordance with the ASTM standard. The tests were conducted in the ambient laboratory atmosphere under a stress ratio R of 0.1.…”

Section: Testingmentioning

confidence: 99%

“…Our research group has designed a harmonic structure using powder metallurgy to sinter mechanically milled stainless steel powders [18][19][20][21][22][23], which improve both their strength and ductility by suppressing necking during tensile deformation [20]. In particular, we have focused on the fatigue properties under fourpoint bending [24][25][26][27] and near-threshold fatigue propagation of long cracks [28][29][30] in titanium-based materials with a bimodal harmonic structure. To achieve sufficient performance with the newly developed harmonic structured stainless steels, their fatigue properties and fatigue crack propagation behavior need to be examined.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of Fatigue Properties under Four-point Bending and Fatigue Crack Propagation in Austenitic Stainless Steel with a Bimodal Harmonic Structure

Kikuchi

Nakatsuka

Nakai

et al. 2019

Frattura Ed Integrità Strutturale

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Austenitic stainless steel (JIS-SUS304L) with a bimodal harmonic structure, which is defined as a coarse-grained structure surrounded by a network of fine grains, was fabricated using powder metallurgy to improve both the strength and ductility. Four-point bending fatigue tests and Kdecreasing tests were conducted in air at room temperature under a stress ratio R of 0.1 to investigate fatigue crack propagation in SUS304L. The fatigue limit of this harmonic-structured material is higher than that of the material with a homogeneous coarse-grained structure. This is attributable to the formation of fine grains by mechanical milling and to the suppression of pore formation. In contrast, the threshold stress intensity range, Kth, for the harmonicstructured material is lower than that for the homogeneous coarse-grained material, while the crack growth rates, da/dN, are higher at comparable K. These results can be attributed to a reduction in the effective threshold stress intensity range, K eff,th , due to the presence of fine grains in the harmonic structure.

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Near‐Threshold Fatigue Crack Propagation in Sintered 304L Stainless Steel Compact with Network Structure Composed of High‐Entropy CrMnFeCoNi Alloy

et al. 2023

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High‐entropy alloys (HEAs) have several superior mechanical properties. However, for these alloys, there is a trade‐off between tensile strength and fatigue‐crack propagation resistance, as is the case for materials with a homogeneous microstructure. The purpose of the present study is to achieve both high‐strength and fatigue‐crack propagation resistance by using a bimodal structure. CrMnFeCoNi alloy and AISI304L powders with different particles diameters are mixed and then consolidated using spark plasma sintering to fabricate sintered compacts with a network structure composed of coarse‐grained 304L surrounded by fine‐grained HEA microstructure. Stress intensity factor K‐decreasing tests are conducted at various force ratios in the ambient laboratory atmosphere to examine near‐threshold fatigue‐crack propagation in the sintered compacts. The ductility and threshold stress intensity range ΔKth tested at a high force ratio for the sintered compacts are higher than that for a homogeneous fine‐grained CrMnFeCoNi alloy. Fatigue cracks in the sintered compacts mainly propagate through the coarse‐grained 304L microstructure, which has high‐fatigue‐crack propagation resistance near the threshold. Therefore, ΔKth for the sintered compacts increases because the ΔKeff,th, which is derived from the 304L without degrading the tensile strength, is higher than that for homogeneous fine‐grained CrMnFeCoNi alloy.

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Effect of harmonic structure design with bimodal grain size distribution on near-threshold fatigue crack propagation in Ti–6Al–4V alloy

Cited by 43 publications

References 23 publications

Effect of bimodal grain size distribution on fatigue properties of Ti-6Al-4V alloy with harmonic structure under four-point bending

Effect of bimodal grain size distribution on fatigue properties of Ti-6Al-4V alloy with harmonic structure under four-point bending

Evaluation of Fatigue Properties under Four-point Bending and Fatigue Crack Propagation in Austenitic Stainless Steel with a Bimodal Harmonic Structure

Near‐Threshold Fatigue Crack Propagation in Sintered 304L Stainless Steel Compact with Network Structure Composed of High‐Entropy CrMnFeCoNi Alloy

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