Effect of boron on the low-cycle fatigue behavior and deformation structure of INCONEL 718 at 650 °C

Xiao, Lin; Chaturvedi, M.C.; Chen, D.L.

doi:10.1007/s11661-004-0185-6

Cited by 31 publications

(17 citation statements)

References 33 publications

(62 reference statements)

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“…[1,2] Alloy IN718 is one of those alloys that exhibit planar slip behavior. [3][4][5][6][7][8][9][10][11][12][13] Planarity of slip is known to be enhanced by shearable precipitates. Thus, planar slip deformation under such microstructural conditions promotes the tendency of strain localization in the initially active slip bands.…”

Section: Introductionmentioning

confidence: 99%

Work-Hardening Behavior of the Ni-Fe Based Superalloy IN718

Kumar

Sastry

Singh

2007

Metall Mater Trans A

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Flow behavior of many metals and alloys in the region of uniform plastic strain is normally expressed by the simple power law relationship (r = Ke p n ). However, deviations have been observed from such behavior in several fcc metallic materials with low stacking fault energy. The age-hardenable nickel-iron base superalloy IN718 is also observed not to obey the simple power law relationship either in the solution treated as well as in the different age-hardened conditions. Various flow relationships were used to obtain the best fit for the experimental data, and different relationships were identified for the different heat-treated conditions. Detailed transmission electron microscopy (TEM) examination of the tensile-tested samples, interrupted after different amounts of strain, revealed inhomogeneous deformation by planar slip in all the heattreated conditions. Cold rolling, however, was found effective in eliminating the unusual plastic flow behavior, observed in the as-heat-treated conditions.

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Section: Introductionmentioning

confidence: 99%

Work-Hardening Behavior of the Ni-Fe Based Superalloy IN718

Kumar

Sastry

Singh

2007

Metall Mater Trans A

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“…To date, only a few studies have reported the influence of B on either the microscopic deformation mechanism or the low-cycle fatigue (LCF) properties of nickel-base superalloys. [15] It was, therefore, considered necessary to further study the effect of B on the plastic deformation mechanism, especially at room temperature (RT), at which the grain boundaries may not play a significant role in plastic deformation of IN 718 and especially during LCF, which was the primary goal of this work.…”

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confidence: 99%

Low-cycle fatigue behavior of INCONEL 718 superalloy with different concentrations of boron at room temperature

Lin

Chaturvedi

Chen

2005

Metall Mater Trans A

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Symmetrical push-pull low-cycle fatigue (LCF) tests were performed on INCONEL 718 superalloy containing 12, 29, 60, and 100 ppm boron (B) at room temperature (RT). The results showed that all four of these alloys experienced a relatively short period of initial cyclic hardening, followed by a regime of softening to fracture at higher cyclic strain amplitudes (⌬ t /2 Ն 0.8 pct). As the cyclic strain amplitude decreased to ⌬ t /2 Յ 0.6 pct, a continuous cyclic softening occurred without the initial cyclic hardening, and a nearly stable cyclic stress amplitude was observed at ⌬ t /2 ϭ 0.4 pct. At the same total cyclic strain amplitude, the cyclic saturation stress amplitude among the four alloys was highest in the alloy with 60 ppm B and lowest in the alloy with 29 ppm B. The fatigue lifetime of the alloy at RT was found to be enhanced by an increase in B concentration from 12 to 29 ppm. However, the improvement in fatigue lifetime was moderate when the B concentration exceeded 29 ppm B. A linear relationship between the fatigue life and cyclic total strain amplitude was observed, while a "two-slope" relationship between the fatigue life and cyclic plastic strain amplitude was observed with an inflection point at about ⌬ p /2 ϭ 0.40 pct. The fractographic analyses suggested that fatigue cracks initiated from specimen surfaces, and transgranular fracture, with well-developed fatigue striations, was the predominant fracture mode. The number of secondary cracks was higher in the alloys with 12 and 100 ppm B than in the alloys with 29 and 60 ppm B. Transmission electron microscopy (TEM) examination revealed that typical deformation microstructures consisted of a regularly spaced array of planar deformation bands on {111} slip planes in all four alloys. Plastic deformation was observed to be concentrated in localized regions in the fatigued alloy with 12 ppm B. In all of the alloys, ␥Љ precipitate particles were observed to be sheared, and continued cyclic deformation reduced their size. The observed cyclic deformation softening was associated with the reduction in the size of ␥ Љ precipitate particles. The effect of B concentration on the cyclic deformation mechanism and fatigue lifetime of IN 718 was discussed.

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“…In all the fatigue tests conducted in this study, the cycling frequency was f cycle = 2 Hz and the load ratio ( min / max in LCF and min / max in HCF) was R = 0.1. The nominal life of the fully hardened IN718 material exposed to VLCF was estimated as N VLCF = 250 cycles [15][16][17][18]. Seven specimens were low-cycle fatigued (LCF) under more typical peak strain of max = 1.2%.…”

Section: -4mentioning

confidence: 99%