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

Makineni, Surendra Kumar; Lenz, Malte; Kontis, Paraskevas; Li, Zhuangming; Kumar, Ankit; Felfer, Peter; Neumeier, Steffen; Herbig, Michael; Spiecker, Erdmann; Raabe, Dierk; Gault, Baptiste

doi:10.1007/s11837-018-2802-7

Cited by 59 publications

(27 citation statements)

References 34 publications

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“…This enrichment is due to segregation of solutes at dislocations, which has been previously reported in APT studies conducted on various materials [24][25][26] and has been unambiguously confirmed by correlative transmission electron microscopy (TEM) and APT analysis. [27,28] A cylindrical region of interest perpendicular to the dislocation, labeled as arrow #1 in Figure 6 Similar observations regarding the segregation and diffusion of chromium and cobalt along dislocations were revealed by APT for two other different nickel-based superalloys. [29] The segregation of chromium and cobalt to dislocations was therein assumed to result in local chemical inhomogeneities and drain these elements from the c matrix.…”

Section: Dissolution Of C¢ Precipitatessupporting

confidence: 67%

The Role of Oxidized Carbides on Thermal-Mechanical Performance of Polycrystalline Superalloys

Kontis

Segersäll

et al. 2018

Metall Mater Trans A

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Oxidized MC carbides which act as main crack initiation sites in a polycrystalline superalloy under thermal-mechanical fatigue (TMF) conditions at 850°C were studied. Microstructural observations in the TMF tested specimens were compared to findings from bulk samples exposed isothermally in air at 850°C for 30 hours in the absence of any external applied load. Carbides were found to oxidize rapidly after exposure at 850°C for 30 hours resulting in surface eruptions corresponding to oxidation products, from where micro-cracks initiated. Plastic deformation due to volume expansion of the often porous oxidized carbides led to high dislocation densities in the adjacent matrix as revealed by controlled electron channeling contrast imaging. The high dislocation density facilitated the dissolution kinetics of c¢ precipitates by segregation and diffusion of chromium and cobalt along the dislocations via pipe diffusion, resulting in the formation of soft recrystallized grains. Atom probe tomography revealed substantial compositional differences between the recrystallized grains and the adjacent undeformed c matrix. Similar observations were made for the TMF tested alloy. Our observations provide new insights into the true detrimental role of oxidized MC carbides on the crack initiation performance of polycrystalline superalloys under TMF.

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Section: Dissolution Of C¢ Precipitatessupporting

confidence: 67%

The Role of Oxidized Carbides on Thermal-Mechanical Performance of Polycrystalline Superalloys

Kontis

Segersäll

et al. 2018

Metall Mater Trans A

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“…Atomic-scale compositional analysis was carried out using atom probe tomography. Site-specific specimens were fabricated using a dual beam SEM/focused-ion-beam (FIB) instrument (FEI Helios NanoLab 600i) in conjunction with an in-situ lift-out method [40]. In order to protect from the Ga ion damage during milling, first, a platinum (Pt) layer of~200 nm thickness was deposited on the region-of-interest (ROI).…”

Section: Atom Probe Tomography (Apt)mentioning

confidence: 99%

On the origin of a remarkable increase in the strength and stability of an Al rich Al-Ni eutectic alloy by Zr addition

et al. 2019

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The effect of Zr addition to Al rich binary a-Al-Al 3 Ni eutectic cast alloy (Al-3.1 at.% Ni) in enhancing the microstructural stability and strength at high temperature is demonstrated. On subsequent heat treatment after casting, nanometric coherent L1 2 ordered Al 3 Zr precipitates form inside the a-Al that strengthen the alloy. Additionally, remarkable stability of eutectic microstructure was observed even after 100 h of annealing at 400 C. The synergetic effect of the strengthening of the a-Al matrix by coherent Al 3 Zr precipitates and the low coarsening rate of the Al 3 Ni rods results in a significant increase in high temperature hardness and yield strength of the alloy. The tensile yield strength of the annealed Al-3.1Ni-0.15Zr alloy (400 C, 10 h) tested at 250 C is found to be 185 ± 10 MPa, which is 1.5 times higher than the corresponding binary Al-3.1Ni alloy. The experimentally determined average rod size (radius) during annealing at 400 C follows the classical matrix diffusion controlled LSW-based coarsening model for both binary Al-3.1Ni and ternary Al-3.1Ni-0.15Zr alloys. The calculated coarsening rate constant values based on modified LSW coarsening model are 10.3 and 4.1 nm 3 /s for Al-3.1Ni and Al-3.1Ni-0.15Zr alloys, respectively. Atom probe tomographic (APT) investigations of the heat-treated ternary alloy unambiguously reveal segregation of Zr solute at the aAl/Al 3 Ni interface in addition to the presence of the strengthening Al 3 Zr ordered precipitates in the a-Al matrix. The segregation hinders the interdiffusion of Al and Ni in the eutectic and, thereby, increasing the stability of the eutectic phase at high temperature.

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“…We have also turned our attention to deformed microstructures in Ni-based superalloys exhibiting a /' microstructure [53][54][55] . In a recent article, we reported on the strong segregation of  stabilizing elements, primarily Cr and Co onto a complex network of linear features appearing within ' precipitates in various alloys, incl.…”

Section: Line Defects Near Oxidized Carbides In Ni-based Superalloysmentioning

confidence: 99%

Interfaces and defect composition at the near-atomic scale through atom probe tomography investigations

et al. 2018

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

Cited by 59 publications

References 34 publications

The Role of Oxidized Carbides on Thermal-Mechanical Performance of Polycrystalline Superalloys

The Role of Oxidized Carbides on Thermal-Mechanical Performance of Polycrystalline Superalloys

On the origin of a remarkable increase in the strength and stability of an Al rich Al-Ni eutectic alloy by Zr addition

Interfaces and defect composition at the near-atomic scale through atom probe tomography investigations

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