Planar defect formation in the γ′ phase during high temperature creep in single crystal CoNi-base superalloys

Eggeler, Yolita M.; Müller, Julian; Titus, Michael S.; Suzuki, Akihito; Pollock, Tresa M.; Spiecker, Erdmann

doi:10.1016/j.actamat.2016.03.077

Cited by 126 publications

(40 citation statements)

References 49 publications

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“…The bright contrast, with respect to the surrounding lattice, along the SF indicates segregation of heavy elements. 30,31 Figure 3c shows a high-resolution STEM image revealing the D0 19 ordered structure of the fault plane surrounded by the L1 2 c¢ precipitate. 31,32 A missing A-type plane as visible in Fig.…”

Section: Methods (2) Cecci-guided In-plane Target Preparation For Tem mentioning

confidence: 99%

Correlative Microscopy—Novel Methods and Their Applications to Explore 3D Chemistry and Structure of Nanoscale Lattice Defects: A Case Study in Superalloys

Makineni

Lenz

Kontis

et al. 2018

JOM

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Section: Methods (2) Cecci-guided In-plane Target Preparation For Tem mentioning

confidence: 99%

Correlative Microscopy—Novel Methods and Their Applications to Explore 3D Chemistry and Structure of Nanoscale Lattice Defects: A Case Study in Superalloys

Makineni

Lenz

Kontis

et al. 2018

JOM

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“…In the ten years since this discovery, considerable work has been performed to gain an enhanced understanding of the behaviour of these materials and develop commercially viable alloys. This research has included studies of the phase equlibria and the effect of alloying [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27], evaluation of their deformation behaviour [22,[28][29][30][31][32][33][34][35][36][37][38][39][40][41], and assessment of their environmental resistance [42][43][44]. However, despite exhibiting several beneficial attributes, further development is still required before any of these alloys can compete with existing Ni-based superalloys.…”

Section: Introductionmentioning

confidence: 99%

The microstructure and hardness of Ni-Co-Al-Ti-Cr quinary alloys

Christofidou

Jones

Pickering

et al. 2016

Journal of Alloys and Compounds

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The effects of Ni:Co and Al:Ti ratios on the room temperature microstructure, hardness and lattice parameter of twenty-seven quinary Ni-Co-Al-Ti-Cr alloys have been evaluated. All of the alloys exhibited a uniform γ-γ′ microstructure. Differential scanning calorimetry (DSC) showed that the liquidus and solidus temperatures of the alloys, increase with greater Al:Ti ratios, decrease with Cr concentration and remained largely unchanged with respect to the Ni:Co ratio. Neutron diffraction measurements of the γ and γ′ lattice parameters revealed that the lattice misfit in all of the alloys was positive and increased with Ti concentration (i.e. lower Al:Ti ratio) regardless of the concentration of Cr, or the ratio of Ni:Co. Importantly, alloys with a Ni:Co ratio of 1:1, were found to have consistently greater lattice misfits than alloys with Ni:Co ratios of either 1:3 or 3:1. The measured lattice misfits were found to be strongly correlated with the Vickers hardness of the alloys, suggesting that lattice misfit plays a key role in the strengthening of γ-γ′ alloys of this type.

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“…However, this mechanism identified in our work differs from that reported recently for the creep of Co-base alloys at 900°C. [13][14][15] The authors found c9 cutting by a/2h011i and a/2h112i dislocations, accompanied by the formation of APBs and stacking faults. Here, one should notice that a stress level applied in our case, 196 MPa, is significantly lower than stress levels applied in Refs.…”

Section: Constant-rate Creep Curves and Dislocation Micromechanismmentioning

confidence: 99%

“…This could permit high-temperature processing, e.g., forging or rolling, assuming that these alloys could be developed as wrought or sheet materials.Research activities on these new Co-based alloys include: alloy development, 1-7 mechanical testing, 2-8 testing of structural stability 9,10 and oxidation, 2,11 and investigations of deformation micromechanisms. 3,[12][13][14][15] At the current stage of alloy development, several Co-base alloys have been proposed, which have creep strengths at temperatures 800-900°C approaching those of Ni-base superalloys, e.g., Refs. 3-5.…”

mentioning

confidence: 99%

Creep behavior of a γ′-strengthened Co-base alloy with zero γ/γ′-lattice misfit at 800 °C, 196 MPa

et al. 2017

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Deformation and structural behavior of an experimental c9-strengthened Co-base alloy during creep at 800°C and 196 MPa have been investigated. The characteristic features of this alloy are zero c/c9-lattice misfit and a fine c/c9-microstructure. In the initial condition, the c9-precipitates in this alloy are small (size of about 100 nm), have polyhedral morphology, and are separated by the very narrow c-channels (width of about 10 nm). The tests performed up to about 1% creep strain (about 500 h creep time) gave creep curves with a slow constant strain rate and without an apparent transient creep, typical for superalloys with nonzero misfit. In this initial stage of creep, entering of the narrow c-channels by dislocations is blocked by a strong Orowan force. The micromechanism of creep was identified as an octahedral glide of h011i superdislocations simultaneously in two phases, c and c9. The c/c9-microstructure with zero misfit shows no rafting but rapidly coarsens isotropically. It is concluded that zero misfit is beneficial at the initial stages of the creep but is unfavourable for longterm creep because of the continuous microstructural coarsening.Recently, Co-base alloys with a c/c9-microstructure similar to that of Ni-base superalloys were discovered. 1 In these Co-base alloys, a face-centred cubic (fcc) solid solution of Co, c, is strengthened by precipitation of a stable ternary Co 3 (Al,W) intermetallic compound, c9, with the ordered structure L1 2 (Cu 3 Au type). It is assumed that these new c9-strengthened Co-base alloys can substitute the Ni-base superalloys in some important applications. The reasons for this assumption are:(i) The discovered Co-base alloys have higher solidus and liquidus temperatures compared with those of Nibase superalloys, which makes them potentially attractive for high-temperature applications.(ii) These Co-base alloys have good castability due to the narrow solidification interval and a low degree of segregation during solidification. This is important for manufacturing of the large single-crystal blades needed for power gas turbines.(iii) These Co-base alloys are c single phase in a wide temperature interval, and the material is then soft and ductile. This could permit high-temperature processing, e.g., forging or rolling, assuming that these alloys could be developed as wrought or sheet materials.Research activities on these new Co-based alloys include: alloy development, 1-7 mechanical testing, 2-8 testing of structural stability 9,10 and oxidation, 2,11 and investigations of deformation micromechanisms. 3,[12][13][14][15] At the current stage of alloy development, several Co-base alloys have been proposed, which have creep strengths at temperatures 800-900°C approaching those of Ni-base superalloys, e.g., Refs. 3-5.

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Planar defect formation in the γ′ phase during high temperature creep in single crystal CoNi-base superalloys

Cited by 126 publications

References 49 publications

Correlative Microscopy—Novel Methods and Their Applications to Explore 3D Chemistry and Structure of Nanoscale Lattice Defects: A Case Study in Superalloys

Correlative Microscopy—Novel Methods and Their Applications to Explore 3D Chemistry and Structure of Nanoscale Lattice Defects: A Case Study in Superalloys

The microstructure and hardness of Ni-Co-Al-Ti-Cr quinary alloys

Creep behavior of a γ′-strengthened Co-base alloy with zero γ/γ′-lattice misfit at 800 °C, 196 MPa

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