Some comparative observations of carbide precipitation morphology related to coherent twin boundaries and high-energy grain boundaries in stainless steels

1993 ◽  
Vol 51 ◽  
pp. 1166-1167
Author(s):  
R. J. Romero ◽  
E. A. Trillo ◽  
A. H. Advani ◽  
L. E. Murr ◽  
W. W. Fisher
Keyword(s):  
Grain Boundaries ◽  
Stainless Steels ◽  
High Energy ◽  
Carbide Precipitation ◽  
304 Stainless Steel ◽  
Twin Boundaries ◽  
Transmission Electron ◽  
Wide Range ◽  
Annealing Twins ◽  
Precipitation Morphology

Stickler and Vinckier showed more than three decades ago that there is a very consistent relationship between the boundaries upon which carbides (M23 C6) precipitate in 300 series stainless steels (having carbon contents ranging from 0.02 to 0.08 wt%). For example, carbides first appear on regular (high-energy) grain boundaries, then non-coherent boundaries and steps on annealing twins, and finally on coherent twin boundaries at a constant temperature above about 600° C, and at aging times which, correspondingly, change by orders of magnitude (1,10, 100 hrs. respectively at 675°C for 304 stainless steel). We have examined a wide range of precipitation features on these various boundaries in 316 and 304 stainless steels which have not been described previously because there have been limited observations comparing carbide morphologies in the transmission electron microscope (TEM) for high-energy grain boundaries (γgb ∼ 800 mJ/m2), non-coherent steps on twin boundaries (γTB ∼ 200 mJ/m2), and coherent twin boundaries (γtb ∼ 20 mJ/m2) for 316 and 304 stainless steels.

Carbide precipitation and chromium depletion on coherent twin boundaries in deformed 304 stainless steels

1992 ◽  
Vol 50 (2) ◽  
pp. 1216-1217
Author(s):  
A.H. Advani ◽  
L.E. Murr ◽  
D.J. Matlock ◽  
W.W. Fisher ◽  
P.M. Tarin ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Stainless Steels ◽  
Interfacial Free Energy ◽  
Carbide Precipitation ◽  
Twin Boundaries ◽  
Invariant Structure ◽  
Heat Treated ◽  
Constant Structure ◽  
Cr Depletion

Coherent annealing-twin boundaries are constant structure and energy interfaces with an average interfacial free energy of ∼19mJ/m2 versus ∼210 and ∼835mJ/m2 for incoherent twins and “regular” grain boundaries respectively in 304 stainless steels (SS). Due to their low energy, coherent twins form carbides about a factor of 100 slower than grain boundaries, and limited work has also shown differences in Cr-depletion (sensitization) between twin versus grain boundaries. Plastic deformation, may, however, alter the kinetics and thermodynamics of twin-sensitization which is not well understood. The objective of this work was to understand the mechanisms of carbide precipitation and Cr-depletion on coherent twin boundaries in deformed SS. The research is directed toward using this invariant structure and energy interface to understand and model the role of interfacial characteristics on deformation-induced sensitization in SS. Carbides and Cr-depletion were examined on a 20%-strain, 0.051%C-304SS, heat treated to 625°C-4.5h, as described elsewhere.

Oriented attachment induces fivefold twins by forming and decomposing high-energy grain boundaries

Science ◽  
2019 ◽  
Vol 367 (6473) ◽  
pp. 40-45 ◽  
Author(s):  
Miao Song ◽  
Gang Zhou ◽  
Ning Lu ◽  
Jaewon Lee ◽  
Elias Nakouzi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Boundaries ◽  
Palladium Nanoparticles ◽  
High Energy ◽  
Oriented Attachment ◽  
Transmission Electron ◽  
Wide Range ◽  
Dynamics Simulations

Natural and synthetic nanoparticles composed of fivefold twinned crystal domains have distinct properties. The formation mechanism of these fivefold twinned nanoparticles is poorly understood. We used in situ high-resolution transmission electron microscopy combined with molecular dynamics simulations to demonstrate that fivefold twinning occurs through repeated oriented attachment of ~3-nanometer gold, platinum, and palladium nanoparticles. We discovered two different mechanisms for forming fivefold twinned nanoparticles that are driven by the accumulation and elimination of strain. This was accompanied by decomposition of grain boundaries and the formation of a special class of twins with a net strain of zero. These observations allowed us to develop a quantitative picture of the twinning process. The mechanisms provide guidance for controlling twin structures and morphologies across a wide range of materials.

MICROSTRUCTURE AND FUNCTIONAL PROPERTY CHANGES IN THIN Ni–Ti WIRES HEAT TREATED BY ELECTRIC CURRENT — HIGH ENERGY X-RAY AND TEM INVESTIGATIONS

2009 ◽  
Vol 02 (02) ◽  
pp. 45-54 ◽  
Author(s):  
B. MALARD ◽  
J. PILCH ◽  
P. SITTNER ◽  
V. GARTNEROVA ◽  
R. DELVILLE ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Electric Current ◽  
High Energy ◽  
X Ray ◽  
Transmission Electron ◽  
Conventional Heat Treatment ◽  
Wide Range ◽  
Millisecond Range ◽  
Property Changes ◽  
Evolution Of Microstructure

High energy synchrotron X-ray diffraction, transmission electron microscopy and mechanical testing were employed to investigate the evolution of microstructure, texture and functional superelastic properties of 0.1 mm thin as drawn Ni – Ti wires subjected to a nonconventional heat treatment by controlled electric current (FTMT-EC method). As drawn Ni – Ti wires were prestrained in tension and exposed to a sequence of short DC power pulses in the millisecond range. The annealing time in the FTMT-EC processing can be very short but the temperature and force could be very high compared to the conventional heat treatment of SMAs. It is shown that the heavily strained, partially amorphous microstructure of the as drawn Ni – Ti wire transforms under the effect of the DC pulse and tensile stress into a wide range of annealed nanosized microstructures depending on the pulse time. The functional superelastic properties and microstructures of the FTMT-EC treated Ni – Ti wire are comparable to those observed in straight annealed wires.

Analysis of Grain Boundaries, Twin Boundaries and Te Precipitates in Cd1−xZnxTe Grown bY High-Pressure Bridgman Method

1997 ◽  
Vol 487 ◽  
Author(s):  
J. R. Heffelfinger ◽  
D. L. Medlin ◽  
R. B. James
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Light Microscopy ◽  
Grain Boundaries ◽  
Local Density ◽  
Infrared Light ◽  
High Angle ◽  
Twin Boundaries ◽  
Transmission Electron ◽  
Te Precipitates

AbstractGrain boundaries and twin boundaries in commercial Cd1−xZnxTe, which is prepared by a high-pressure Bridgeman technique, have been investigated with transmission electron microscopy, scanning electron microscopy, infrared-light microscopy and visible-light microscopy. Boundaries inside these materials were found to be decorated with Te precipitates. The shape and local density of the precipitates were found to depend on the particular boundary. For precipitates that decorate grain boundaries, their microstructure was found to consist of a single, saucer-shaped grain of hexagonal Te (space group P3121). Analysis of a Te precipate by selected-area diffraction revealed the Te to be aligned with the surrounding Cd1−xZnxTe grains. This alignment was found to match the (111) Cd1−xZnxTe planes with the (0111) planes of hexagonal Te. Crystallographic alignments between the Cd1−xZnxTe grains were also observed for a high-angle grain boundary. The structures of the grain boundaries and the Te/C1−xZnxTe interface are discussed.

Analysis of Grain Boundaries, Twin Boundaries and Te Precipitates in Cd1−xZnxTe Grown by High-Pressure Bridgman Method

1997 ◽  
Vol 484 ◽  
Author(s):  
J. R. Heffelfinger ◽  
D. L. Medlin ◽  
R. B. James
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Light Microscopy ◽  
Grain Boundaries ◽  
Local Density ◽  
Infrared Light ◽  
High Angle ◽  
Twin Boundaries ◽  
Transmission Electron ◽  
Te Precipitates

AbstractGtain boundaries and twin boundaries in commercial Cd1−xZnxTe, which is prepared by a high-pressure Bridgeman technique, have been investigated with transmission electron microscopy, scanning electron microscopy, infrared-light microscopy and visible-light microscopy. Boundaries inside these materials were found to be decorated with Te precipitates. The shape and local density of the precipitates were found to depend on the particular boundary. For precipitates that decorate grain boundaries, their microstructure was found to consist of a single, saucer-shaped grain of hexagonal Te (space group P3,2 1). Analysis of a Te precipate by selected-area diffraction revealed the Te to be aligned with the surrounding Cd1−xZnxTe grains. This alignment was found to match the (111) Cd1−xZxTe planes with the (0 111) planes of hexagonal Te. Crystallographic alignments between the Cd1−xZnxTe grains were also observed for a high-angle grain boundary. The structures of the grain boundaries and the Te/Cd1−xZnxTe interface are discussed.

TEM Observations of Dislocation Emission at Grain Boundaries in Response to Uniaxial (Tensile) Straining

1981 ◽  
Vol 39 ◽  
pp. 296-297
Author(s):  
L.E. Murr
Keyword(s):  
Grain Boundaries ◽  
Tensile Deformation ◽  
Tensile Tests ◽  
Convincing Evidence ◽  
304 Stainless Steel ◽  
Uniaxial Tensile ◽  
Dislocation Emission ◽  
Quantitative Studies ◽  
Transmission Electron

Although it now seems to be generally recognized that grain boundaries and other interfaces are sources for dislocations, there are only scant few observations which tend to show convincing evidence for this. Murr earlier suggested that dislocation pile-ups in deformed metals and alloys (especially of low stacking-fault free energy) were primarily dislocation emission profiles, and more recent quantitative studies tend to unambiguously confirm this for uniaxial tensile deformation. Some of these features are illustrated in Fig. 1(a) and (b) which show a systematic increase in the number of dislocation profiles associated with grain boundary ledges at increasing tensile strains; observed in a Hitachi H.U. 200 F transmission electron microscope.The results shown in Fig. 1(a) and (b) were obtained as part of a systematic study of dislocation emission following the straining of 304 stainless steel sheet samples in separate, conventional tensile tests. Consequently these observations, while qualitatively and even quantitatively convincing, lack the force of direct, in-situ observations.

Structure and Grain Boundaries of Ultrafine-Grained Nickel after Rolling and Forging at Cryogenic Temperature

2021 ◽  
Vol 313 ◽  
pp. 31-40
Author(s):  
Evgeny V. Naydenkin ◽  
Ivan P. Mishin
Keyword(s):  
Grain Boundaries ◽  
Cryogenic Temperature ◽  
Liquid Nitrogen Temperature ◽  
Deformation Bands ◽  
Localized Deformation ◽  
Twin Boundaries ◽  
Fragmented Structure ◽  
Ultrafine Grained ◽  
Annealing Twins ◽  
Small Grains

The structure and misorientations of grain boundaries of ultrafine-grained nickel subjected to rolling and forging at liquid nitrogen temperature are studied. It is shown that as a result of rolling in UFG nickel obtained by the ECAP the forming of a band fragmented structure with the formation of special twin boundaries Σ3 is observed. An increase in the strain rate (forging) leads to the appearance of localized deformation bands in which the formation of new small grains is observed through dynamic recrystallization. The development of recrystallization results in increase up to 7% in UFG nickel the fraction of special twin boundaries Σ3 which are similar in nature to annealing twins.

scholarly journals Measurement of Oxygen Disorder and Nano-Twin Microstructure Associated with Columnar Defects In Ybco

1998 ◽  
Vol 540 ◽  
Author(s):  
Y. Yan ◽  
T. Walther ◽  
M.A. Kirk
Keyword(s):  
Ion Irradiation ◽  
Heavy Ion ◽  
High Energy ◽  
High Dose ◽  
Twin Boundaries ◽  
High Tc ◽  
Heavy Ion Irradiation ◽  
Transmission Electron ◽  
Columnar Defects ◽  
Lattice Images

AbstractStudies of defects generated by high energy (>1 GeV) heavy ion irradiation in high-Tc superconductors have been performed by transmission electron microscopy (TEM). Our study shows that high dose irradiation leads to the formation of nano-twins, by which the columnar defects are connected. An analysis of the local Fourier components of the image intensity in [001] lattice images indicates that these new "twin" boundaries are much more diffuse than preexisting twin boundaries in YBCO. The mechanism of the formation of nano-twin boundaries on {110} planes and their possible relation to superconducting properties are discussed.

scholarly journals Transmission Electron Microscopy Study on the Precipitation Behaviors of Laser-Welded Ferritic Stainless Steels and Their Implications on Intergranular Corrosion Resistance

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 86
Author(s):  
Niklas Sommer ◽  
Clementine Warres ◽  
Tarek Lutz ◽  
Martin Kahlmeyer ◽  
Stefan Böhm
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Boundaries ◽  
Stainless Steels ◽  
Intergranular Corrosion ◽  
Microscopy Study ◽  
Precipitation Behavior ◽  
Acid Media ◽  
Ferritic Stainless Steels ◽  
Transmission Electron

The intergranular corrosion susceptibility of ferritic stainless-steel weldments is strongly dependent on chromium carbide precipitation phenomena. Hence, stabilization is widely used to mitigate the aforementioned precipitation. In contrast, stabilization has proved ineffective to fully prevent intergranular corrosion due to segregation of unreacted chromium during solid-state heat-treatments. To analyze the precipitation behavior of 17 wt.-% chromium ferritic stainless steels during laser welding, sheets of unstabilized and titanium-stabilized ferritic stainless steels were welded in a butt joint configuration and characterized with special consideration of precipitation behavior by means of transmission electron microscopy. While unstabilized ferritic stainless steels exhibit pronounced chromium precipitate formation at grain boundaries, titanium-stabilization leads to titanium precipitates without adjacent chromium segregation. However, corrosion tests reveal three distinctive corrosion mechanisms within the investigated ferritic stainless steels based on their inherent precipitation behaviors. In light of the precipitation formation, it is evident that immersion in sulfuric acid media leads to the dissolution of either grain boundaries or the grain boundary vicinity. As a result, the residual mechanical strength of the joint is substantially degraded.

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