In-Situ TEM Observation of Crack Propagation in a Single Crystal Ni3Al

An in situ scanning electron microscope (SEM) tensile test for Ni-based single-crystal superalloy was carried out at 1000 °C. The stress displacement was obtained, and the yield strength and tensile strength of the superalloy were 699 MPa and 826 MPa, respectively. The crack propagation process, consisting of Model I crack and crystallographic shearing crack, was determined. More interestingly, the crack propagation path and rate affected by eutectics was directly observed and counted. Results show that the coalescence of the primary crack and second microcrack at the interface of a γ/γ′ matrix and eutectics would make the crack propagation rate increase from 0.3 μm/s to 0.4 μm/s. On the other hand, crack deflection decreased the rate to 0.05 μm/s. Moreover, movement of dislocations in front of the crack was also analyzed to explain the different crack propagation behavior in the superalloy.

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Fracture in Bulk Amorphous Alloys

MRS Proceedings ◽

10.1557/proc-554-185 ◽

1998 ◽

Vol 554 ◽

Cited By ~ 5

Author(s):

J. A. Horton ◽

J. L. Wright ◽

J. H. Schneibel

Keyword(s):

Crack Propagation ◽

Crack Growth ◽

Shear Bands ◽

Bulk Amorphous Alloy ◽

In Situ Tem ◽

X Ray Diffraction ◽

Transmission Electron ◽

Crack Tips ◽

Temperature Fracture

AbstractThe fracture behavior of a Zr-based bulk amorphous alloy, Zr-10 Al-5 Ti-17.9 Cu-14.6Ni (at.%), was examined by transmission electron microscopy (TEM) and x-ray diffraction forany evidence of crystallization preceding crack propagation. No evidence for crystallizationwas found in shear bands in compression specimens or at the fracture surface in tensile specimens.In- situ TEM deformation experiments were performed to more closely examine actualcrack tip regions. During the in-situ deformation experiment, controlled crack growth occurredto the point where the specimen was approximately 20 μm thick at which point uncontrolledcrack growth occurred. No evidence of any crystallization was found at the crack tips or thecrack flanks. Subsequent scanning microscope examination showed that the uncontrolledcrack growth region exhibited ridges and veins that appeared to have resulted from melting. Performing the deformations, both bulk and in-situ TEM, at liquid nitrogen temperatures (LN2) resulted in an increase in the amount of controlled crack growth. The surface roughness of the bulk regions fractured at LN2 temperatures corresponded with the roughness of the crack propagation observed during the in-situ TEM experiment, suggesting that the smooth-appearing room temperature fracture surfaces may also be a result of localized melting.

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Comments on “In-situ TEM study of crack propagation in crystal thinning area and crystal rotation at crack tip in Al” by Kang Yan and Zhongwei Chen et al. [Mater. Sci. Eng. A 824 (2021) 141800]

Materials Science and Engineering A ◽

10.1016/j.msea.2021.142266 ◽

2021 ◽

pp. 142266

Author(s):

Kenton N. Gould

Keyword(s):

Crack Propagation ◽

Crack Tip ◽

In Situ Tem ◽

Crystal Rotation

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In situ TEM oxidation study of Fe thin-film transformation to single-crystal magnetite nanoparticles

Journal of Materials Science ◽

10.1007/s10853-020-04917-8 ◽

2020 ◽

Vol 55 (27) ◽

pp. 12897-12905

Author(s):

Leonardo Lari ◽

Stephan Steinhauer ◽

Vlado K. Lazarov

Keyword(s):

Thin Film ◽

Single Crystal ◽

Magnetite Nanoparticles ◽

In Situ Tem ◽

Oxidation Study

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Phase Transformations in the Fe-Al System Studied by “In-Situ” Tem Heating

MRS Proceedings ◽

10.1557/proc-364-219 ◽

1994 ◽

Vol 364 ◽

Cited By ~ 2

Author(s):

A. Korner

Keyword(s):

Transition Temperature ◽

Single Crystal ◽

Domain Structure ◽

Type A ◽

Bimodal Distribution ◽

Dislocation Motion ◽

In Situ Tem ◽

Transmission Electron ◽

The Matrix

AbstractThe domain structure and the evolution of antiphase boundaries (APBs) have been investigated in Fe-Al by means of “in-situ” transmission electron microscopy (TEM) heating experiments. Single crystals with composition Fe22.1at%Al and Fe25.6at%Al have been used.The grown-in structure of the Fe22.1at%al single crystal is composed of DO3 ordered particles embedded in the disorderd ±-matrix. A bimodal distribution of the particles was found. Small ordered particles are in between the large precipitates which are surrounded by particle-free zones. Numerous of this large ordered precipitates contain APBs. Crossing the transition temperature to the disordered phase, the small particles dissolve into the ±-matrix and the large particles start to shrink by dissolving.The single crystal with composition Fe25.6at%Al was found to be completely DO3 ordered. The grown-in domains are separated by APBs of type a′0/2〈100〉. At temperatures far below the transition temperature to the B2 phase no significant change in the APB and domain structure has been detected. In contrast, a remarkable evolution in the APB structure has been observed approaching the transition temperature. Coarsening of the domains has been found. Furthermore, APBs of B2-type (a′0/4〈lll〉 shear) are dragged out by dislocation motion. B2- and DC3-type APBs react and junctions are formed. With increasing annealing time, the density of B2-type boundaries increases. The TEM image is dominated by B2-type boundaries linked by the D03-type boundaries. The DO3 superlattice spots are clearly excited approaching the transition temperature to B2. Above the transition temperature, the DO3 spots disappear completely and the diffraction pattern reveals B2 long range order.

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