Some new aspects concerning particle hardening mechanisms in γ' precipitating Ni-base alloys—I. Theoretical concept

Reppich, Bernd

doi:10.1016/0001-6160(82)90048-7

Cited by 236 publications

(66 citation statements)

References 16 publications

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“…The alloys with higher Nb/Ti ratios show higher peak aging hardness. It is known that precipitate shearing is the main deformation mechanism in alloys for turbine discs [17], and it is expected that Nb would have a significant effect on the APB energy, lattice misfit, microstructure, volume fraction of the γ precipitates, and several other factors influencing strength. However, a previous study of X-ray synchrotron diffraction [21] shows that the lattice misfit almost never changes and that the volume fraction slightly increases as the Nb/Ti ratio increases.…”

Section: Age Hardening Behaviour Of the Abd Alloysmentioning

confidence: 99%

“…It is well established that the shearing of the γ precipitates is the main contributor to the strength of polycrystalline superalloys, as replicated by a dislocation pair model [16,17]. The models describe that interfacial energy associated with an APB is created by a leading dislocation minimised by the passage of the trailing dislocation.…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Nb/Ti Ratio on Hardness in High-Strength Ni-Based Superalloys

Hisazawa

Terada

Adziman

et al. 2017

Metals

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Abstract:The age-hardening behaviour and microstructure development of high strength Ni-based superalloys ABD-D2, D4, and D6 with varying Nb/Ti ratios have been studied. The studied alloys have large volume fractions and multimodal size distributions of the γ precipitates, making them sensitive to cooling conditions following solution heat treatment. Differential scanning calorimetry was conducted with a thermal cycle that replicated a processing heat treatment. The hardness of these alloys was subsequently evaluated by nanoindentation. The Nb/Ti ratio was not observed to influence the size and distribution of primary and secondary γ precipitates; however, the difference in those of tertiary γ and precipitate morphology were observed. The nanoindentation hardness for all alloys reduces once they have been solution-heat-treated. The alloys exhibited specific peak hardness. The alloy with the greatest Nb content was found to have the best increase in hardness among the alloys studied due to its large tertiary γ precipitate.

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Section: Age Hardening Behaviour Of the Abd Alloysmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Effect of Nb/Ti Ratio on Hardness in High-Strength Ni-Based Superalloys

Hisazawa

Terada

Adziman

et al. 2017

Metals

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“…However, it does show the effect of volume fraction and in terms of its qualitative predications is largely in agreement with the simpler theory of Copley and Kear. Other authors have considered the effect of strong and weak coupling of the dislocations [14][15][16][17]. As shown in figure 3, the two 110 -type superpartials appear to be strongly coupled in the precipitate, which influences the effect of particle size on the strength.…”

Section: Monotonic Deformation Of Ni-base Superalloysmentioning

confidence: 99%

Microstructural aspects of fatigue in Ni-base superalloys

Antolovich

2015

Phil. Trans. R. Soc. A.

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Nickel-base superalloys are primarily used as components in jet engines and land-based turbines. While compositionally complex, they are microstructurally simple, consisting of small (50–1000 nm diameter), ordered, coherent Ni 3 (Al,Ti)-type L1 2 or Ni 3 Nb-type DO 22 precipitates (called γ ′ and γ ′′ , respectively) embedded in an FCC substitutional solid solution consisting primarily of Ni and other elements which confer desired properties depending upon the application. The grain size may vary from as small as 2 μm for powder metallurgy alloys used in discs to single crystals the actual size of the component for turbine blades. The fatigue behaviour depends upon the microstructure, deformation mode, environment and cycle time. In many cases, it can be controlled or modified through small changes in composition which may dramatically change the mechanism of damage accumulation and the fatigue life. In this paper, the fundamental microstructural, compositional, environmental and deformation mode factors which affect fatigue behaviour are critically reviewed. Connections are made across a range of studies to provide more insight. Modern approaches are pointed out in which the wealth of available microstructural, deformation and damage information is used for computerized life prediction. The paper ends with a discussion of the very important and highly practical subject of thermo-mechanical fatigue (TMF). It is shown that physics-based modelling leads to significantly improved life prediction. Suggestions are made for moving forward on the critical subject of TMF life prediction in notched components.

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“…The increment would be due to the increase in the volume fraction of secondary ′ precipitates from 0.304 to 0.455 according to a strengthening model for strong coupled pair dislocation [21].…”

Section: Strengthening Mapmentioning

confidence: 99%

New Quantitative Analysis of Contributing Factors to Strength of Disk Superalloys

Osada¹,

Gu²,

Nagashima³

et al. 2012

Superalloys 2012 (Twelfth International Symposium)

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The contributions of multiple strengthening factors to the 0.2% flow stress have been studied in a cast and wrought Ni-Co base disk superalloy with varying grain size, twin fraction and bimodal or trimodal ′ size distributions. The alloy was heat-treated within the ′ sub-and super-solvus temperature ranges between 1100 o C to 1180 o C, followed by two step aging heat-treatment. The contribution of each strengthening factor are analyzed by measuring its Vickers hardness at over a structural scale ranging from nano to micro levels and then by converting the hardness differences to the contribution to the 0.2% flow stress on the basis of the empirical relation:  0.2 =2.46Hv. The results clearly show that the contribution of grain boundary strengthening decreased and reached zero with increasing solution temperature. The behavior followed Hall-Petch effect and Zener's pinning model, and strongly depended on the size and volume fraction of pinning primary ′ that is un-dissolved during solution treatment. Meanwhile, the contributions of secondary and tertiary ′ precipitation strengthening increased with increasing temperature. The behaviors also strongly depend on the volume fraction of the primary ′ since the designed total volume fraction of ′ of the alloy is approximately 0.5. As a result, the combinations of these strengthening factors lead to the maximum flow stress at solution temperature of 1135 o C. This would suggest that the primary ′ plays an important role to optimize the microstructure combination through the solution heat-treatment.

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Some new aspects concerning particle hardening mechanisms in γ' precipitating Ni-base alloys—I. Theoretical concept

Cited by 236 publications

References 16 publications

The Effect of Nb/Ti Ratio on Hardness in High-Strength Ni-Based Superalloys

The Effect of Nb/Ti Ratio on Hardness in High-Strength Ni-Based Superalloys

Microstructural aspects of fatigue in Ni-base superalloys

New Quantitative Analysis of Contributing Factors to Strength of Disk Superalloys

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