On the effect of prior austenite grain size on near-threshold fatigue crack growth

Carlson, M.F.; Ritchie, Robert O.

doi:10.1016/0036-9748(77)90317-9

Cited by 40 publications

(7 citation statements)

References 12 publications

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“…The coincidence of high threshold stress intensity and large prior austenite grain size in Fe/2Si/0.le OFM (IQ) is consistent with the general, but not universal [24], trend of increased grain size giving higher fatigue thresholds in steels [14,17,25,26]. The significance of the prior austenite grain …”

Section: -14 -supporting

confidence: 61%

Effects of microstructure on fatigue crack growth in duplex ferrite-martensite steels

Wasynczuk

Ritchie

Thomas

1984

Materials Science and Engineering

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Monotonic tensile and fatigue crack growth tests have been performed on AISI 1018 and Fe/2Si/l).lC steels with duplex ferrite-martensite (DFM) microstructures. The effects of microstructure on ambient temperature mechanical properties were examined. Two distinct martensite distributions were produced in AISI 1018 DFM. The primary differences between the two were the ferrite and martensite particle sizes. It was found that tensile fracture was sensitive to both martensite distribution and volume fraction. For a given volume fraction of martensite, large particle sizes increased strength but drastically reduced ductility.Threshold stress intensity ranges for fatigue crack growth in AISI 1018 DFM were found to be unaffected by the distribution or the volume fraction of martensite • -5 -3 / However, crack growth rates in the range of 10 to 10 mm cycle were increased in AISI 1018 DFM when the particle sizes were large. The increased crack growth rates were attributed to a crack extension mechanism involving cleavage fracture in ferrite. The Fe/2Si/0.1C DFM alloy was found to have a considerably higher fatigue threshold stress intensity than AISI 1018 DFM of comparable strength. The -2 -greater near-threshold fatigue crack propagation resistance in Fe/2Si/O.le DFM was attributed to a meandering crack path, generated by the coarser microstructure in this steel, which promotes roughness-induced crack closure and crack deflection effects.

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Section: -14 -supporting

confidence: 61%

Effects of microstructure on fatigue crack growth in duplex ferrite-martensite steels

Wasynczuk

Ritchie

Thomas

1984

Materials Science and Engineering

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“…While an increase in AK,,, with ferritic grain size has been observed by several researchers [23, 241 in low C steels, coarsening of the prior austenite grain size in Fe-Cr-C steel actually resulted in a lower AK,, [25]. The austenitic grain size must have been smallest for HY130 because it had the lowest austenitizing temperature and undissolved VC particles give grain refinement.…”

Section: Discussionmentioning

confidence: 86%

Fatigue Macrocrack Growth in Tempered Hy80, Hy130, and 4140 Steels:threshold and Mid-?K Range

Kwun

Fine

1980

Fat Frac Eng Mat Struct

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The rate of propagation of macrofatigue cracks down to near threshold was measured in air in three tempered martensitic steels; HY80, HY130 and 4140 (650°C temper). The value of A&,, was determined by the load-shedding technique in center notched panel specimens. Of the three steels, 4140 tempered at 65WC had the lowest AK,,, 3 3 MN/m3IZ, while HY80 had the highest, 4.2 MN/rn3". The 4140 (650°C temper) is intermediate in strength between HY80 and HY130. The results are discussed in terms of a recent theory of one of the authors.The fatigue crack propagation rates in the mid-AK range in HY80 and HY130 in argon were also studied by measuring, with foil strain gages, the cyclic plastic work to propagate a fatigue crack by a unit area, U . HY80 has a lower crack propqgation rate and correspondingly higher U. This was attributed in part to the higher yield strength of HY130 but the dislocation structure and carbide composition and morphology also play roles. Microstructural changes due to cyclic plastic deformation inside the plastic zone in HY80 and HY130 were observed by TEM of thin foils. SEM studies of the fracture surfaces at AK = 20 MN/m3" indicate a more ductile fracture mode for HYSO than for HY130. The fatigue crack propagation rate of HY130 is substantially higher in laboratory air (47% relative humidity) than in dry argon. This is not the case for HY80.

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“…However, threshold based solely on the yield strength would indicate higher threshold for high-strength materials. In fact, thresholds observed in high-strength steels [23,24] has been shown to be significantly lower compared to thresholds observed in low-and medium-strength steels [4-121. This would tend to suggest that other mechanisms are operable for crack growth and/or threshold in high-strength steels that are not in lower-strength steels. Environmental effects are thought to be influential in governing threshold of high-strength steels [14].…”

Section: Discussionmentioning

confidence: 99%

“…[6] 0.18 219 Ferritic (0.07C) 0.2 1 192 Carlson rt al. [23,24] 0.09 1324 High strength steel 0.09 1324 Tiara rt al. [8] 0 structure size as being the controlling microstructure feature in the determination of threshold in steels.…”

Section: Discussionmentioning

confidence: 99%

A Proposed Criterion for Fatigue Threshold: Dislocation Substructure Approach

Lucas

1983

Fatigue Fract Eng Mat Struct

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A model for fatigue threshold has been proposed based on the dislocation subgrain cell structure that evolves at the crack tip in steels during the fatigue deformation process. The stabilized subgrain cells that develop in the material act as impenetrable barriers to dislocations in slip band pile-ups that emanate from the fatigue crack tip. The blocking of these dislocations tends to limit crack growth that occurs by crack tip emission of dislocations, thereby leading ultimately to the fatigue threshold condition. The grain size effect on threshold is deduced to be an indirect effect as it is proposed that the subgrain cell size is the controlling substructural parameter at the threshold stress intensity level. The subgrain cell size is shown to be proportional to the one-third power of the initial grain size. NOMENCLATURE a = constant b = Burger's vector = constant p, = cyclic strain hardening exponent D = average grain size E = elastic modulus G = shear modulus E , E,,, eya = total, plastic and yield strains AKTH = threshold stress intensity range factor M = Taylor's factor p, = mobile dislocation density Rf = reversed plastic zone size r = length parameter X = subgrain cell size 0 = plasticity factor 6 = constant o y s = yield strength AK = stress intensity range.

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On the effect of prior austenite grain size on near-threshold fatigue crack growth

Cited by 40 publications

References 12 publications

Effects of microstructure on fatigue crack growth in duplex ferrite-martensite steels

Effects of microstructure on fatigue crack growth in duplex ferrite-martensite steels

Fatigue Macrocrack Growth in Tempered Hy80, Hy130, and 4140 Steels:threshold and Mid-?K Range

A Proposed Criterion for Fatigue Threshold: Dislocation Substructure Approach

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