Grain boundary characterization and energetics of superalloys

Sangid, Michael D.; Şehitoğlu, Hüseyin; Maier, Hans Jürgen; Niendorf, Т.

doi:10.1016/j.msea.2010.07.062

Cited by 95 publications

(27 citation statements)

References 68 publications

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“…As shown in Fig. 1, a single grain (of diameter 9 μm) was selected and the GB energy around the PSB was varied from a lower limit of 60 mJ/m 2 (corresponding to a coherent twin) to an upper limit of 932 mJ/m 2 (corresponding to a HAGB, specifically a 38.94°tilt around the [110]) [54], keeping all the other microstructure parameters within the fatigue model constant. The analysis was repeated for a grain cluster (PSB of length 20 μm that spans across a LAGB).…”

Section: Design For Fatigue Enhancementmentioning

confidence: 99%

Tailoring the Properties of a Ni-Based Superalloy via Modification of the Forging Process: an ICME Approach to Fatigue Performance

Detrois

Rotella

Hardy

et al. 2017

Integr Mater Manuf Innov

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Traditionally, material design and property modifications are usually associated with compositional changes. Yet, subtle changes in the manufacturing process parameters can also have a dramatic effect on the resulting material properties. In this work, an integrated computational materials engineering (ICME) framework is adopted to tailor the fatigue performance of a Ni-based superalloy, RR1000. An existing fatigue model is used to identify microstructural features that promote enhanced fatigue life, namely a uniform, fine grain size distribution, random orientation, a distinct grain boundary distribution (specifically high twin boundary density and limited low-angle grain boundaries). A deformation mechanism map and process models for grain boundary engineering of RR1000 are used to identify the optimal thermo-mechanical processing parameters to realize these desirable microstructural features. For validation, small-scale forgings of RR1000 were produced and heat-treated to attain fine grain and coarse grain microstructures that represent the conventionally processed and grain boundary engineered (GBE) conditions, respectively. For each of the four microstructural variants of RR1000, the twin density and grain size were characterized and were in agreement with the desired microstructural attributes. In order to validate the deformation mechanisms and fatigue behavior of the material, high-resolution digital image correlation was performed to generate strain maps relative to the microstructural features. The high density of twin boundaries was confirmed to inhibit the length of slip bands, which is directly attributed to extended fatigue life. Thus, this study demonstrated the successful role of models, both process and performance, in the design and manufacture of Ni-based superalloy disk forgings.

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Section: Design For Fatigue Enhancementmentioning

confidence: 99%

Tailoring the Properties of a Ni-Based Superalloy via Modification of the Forging Process: an ICME Approach to Fatigue Performance

Detrois

Rotella

Hardy

et al. 2017

Integr Mater Manuf Innov

Self Cite

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“…The P-Phase needles grow with a convex curvature and some driving force must be consumed to overcome the pressure associated with the curvature and given by 2 rV m r Â Ã per mole of P Phase, where r is radius of curvature (~0.1 to 1 lm), V m is molar volume [V m~6 .59 cm 3 /mol (for Ni)], and r is the high-angle grain boundary energy (~1.5 J m -2 ). [29] This is estimated to bẽ [0.002 to 0.02] kJ mol À1 of DP¢ (~0.1 mol of P Phase). Therefore, there is a minimal loss of driving force from capillarity and nearly all of the driving force is available to pull the grain boundary.…”

Section: Rejectedmentioning

confidence: 99%

Discontinuous Precipitation in Ni-Base Superalloys During Solution Heat Treatment

Welton

D’Souza

Kelleher

et al. 2015

Metall Mater Trans A

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Discontinuous precipitation in single-crystal Ni-base superalloys during solution heat treatment has been studied. It is found that discontinuous precipitation occurs at temperatures approaching the solvus, where volume diffusion is dominant. Diffusion of Al ahead of the boundary leads to gamma prime precipitation and is accompanied by a loss in the driving force available for advancement of the grain boundary. The rate of gamma prime precipitation was tracked using in situ neutron diffraction during isothermal hold. Gamma prime precipitation is accompanied by super-saturation of Cr and W within the channels ahead of the interface. The driving force calculated for the initial stages of DP was [10-5 to 10-4] N/[lm 2 of the grain boundary]. The results provide an insight into discontinuous precipitation during solution heat treatment of Ni-base single-crystal alloys and are useful in optimizing the heat treatment process to avoid surface defect formation.

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“…We choose the Σ3(111) twist and the Σ5(012) tilt GBs as representative low energy and high energy GBs respectively. Σ3 (111) is formed by cleaving the bulk along the (111) plane, rotating one grain around [111] by 60 0 and rejoining the two parts [25]. It is the lowest energy GB among all coincidence site lattice (CSL) types that differ from bulk by just a stacking fault.…”

Section: Qin Gao and Michael Widommentioning

confidence: 99%

First-principles study of bismuth films at transition-metal grain boundaries

Gao

Widom

2014

Phys. Rev. B

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Recent experiments suggest that Bi impurities segregate to form bilayer films on Ni and Cu grain boundaries but do not segregate in Fe. To explain these phenomena, we study the total energies of Bi films on transition metal (TM) Σ3( 111) and Σ5(012) GBs using density functional theory. Our results agree with the observed stabilities. We propose a model to predict Bi bilayer stability at Ni GBs which suggests that Bi bilayer is not stable on (111) twist CSL GBs but is stable in most (100) twist CSL GBs. We investigate the interaction and bonding character between Bi and TMs to explain the differences among TMs based on localization of orbitals and magnetism.

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Grain boundary characterization and energetics of superalloys

Cited by 95 publications

References 68 publications

Tailoring the Properties of a Ni-Based Superalloy via Modification of the Forging Process: an ICME Approach to Fatigue Performance

Tailoring the Properties of a Ni-Based Superalloy via Modification of the Forging Process: an ICME Approach to Fatigue Performance

Discontinuous Precipitation in Ni-Base Superalloys During Solution Heat Treatment

First-principles study of bismuth films at transition-metal grain boundaries

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