Radiation-Induced Minor Element Segregation at Austenitic Stainless Steel Grain Boundaries

1996 ◽  
Vol 439 ◽  
Author(s):  
E. P. Simonen ◽  
S. M. Bruemmer
Keyword(s):  
Grain Boundaries ◽  
Neutron Irradiation ◽  
Ion Irradiation ◽  
Austenitic Stainless Steels ◽  
Minor Element ◽  
High Rate ◽  
Rate Theory ◽  
Minor Elements ◽  
Radiation Induced ◽  
Irradiation Behavior

AbstractMeasurement of minor element compositions at irradiated grain boundaries in austenitic stainless steels indicates that Si is the only element that significantly responds to radiation-induced segregation. Other minor elements, such as P or S, do not exhibit elevated grain boundary concentrations after irradiation. A rate theory evaluation of segregation is in accord with ioninduced Si enrichment, but reveals complexities in the interpretation of extrapolating behavior from ion-irradiation to neutron-irradiation behavior. The model calibrated to measured high-rate, ioninduced segregation greatly overestimates measured low-rate, neutron-irradiation segregation of Si.

A Phenomenological Model for the Effect of Nanocrystalline Microstructure on Irradiation-Induced Amorphization In U3Si

1994 ◽  
Vol 373 ◽  
Author(s):  
J. Rest
Keyword(s):  
Critical Temperature ◽  
Grain Boundaries ◽  
Ion Irradiation ◽  
Theory Model ◽  
Rate Theory ◽  
Two Phase ◽  
Thermal Crystallization ◽  
Acoustic Shock Wave ◽  
Radiation Induced ◽  
Nanocrystalline Microstructure

AbstractA rate theory model is formulated wherein amorphous clusters are formed by a damage event. These clusters are considered centers of expansion (CEs), or excess-free-volume zones. Simultaneously, centers of compression (CCs) are created in the material. The CCs are local regions of increased density that travel through the material as an elastic (e.g., acoustic) shock wave. The CEs can be annihilated upon contact with a sufficient number of CCs, to form either a crystallized region indistinguishable from the host material, or a region with a slight disorientation (recrystallized grain). Recrystallized grains grow by the accumulation of additional CCs.Preirradiation of U3Si above the critical temperature for amorphization results in the formation of nanometer-size grains. In addition, subsequent reirradiation of these samples in the same ion flux at temperatures below the critical temperature shows that the material has developed a resistance to radiation-induced amorphization (i.e., a higher dose is needed to amorphize preirradiated samples than those that have not been preirradiated). In the model, it is assumed that grain boundaries act as effective sinks for defects, and that enhanced defect annihilation is responsible for retarding amorphization below the critical temperature by, for example, preventing a buildup of vacancies adjacent to the grain boundaries. The calculations have been validated against data from ion-irradiation experiments with U3Si. For appropriate values of the activation energy of thermal crystallization, the model predicts the evolution of a two phase microstructure consisting of nanocrystalline grains and amorphous clusters.

Effect of Mesostructural Elements on Radiation-Induced Porosity in 16Cr-19Ni-2Mo-2Mn-Nb-Ti-V-P-B Austenitic Steel

2019 ◽  
Vol 946 ◽  
pp. 357-361
Author(s):  
Vladimir I. Pastukhov ◽  
Irina A. Portnykh ◽  
Mikhail L. Lobanov
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Grain Boundaries ◽  
Austenitic Steel ◽  
Neutron Irradiation ◽  
Steel Structure ◽  
Void Size ◽  
Orientation Microscopy ◽  
Radiation Induced ◽  
Scanning Electron

Different mesostructural elements of 16Cr-19Ni-2Mo-2Mn-Nb-Ti-B austenitic steel have been examined after neutron irradiation to damage dose up to 82 dpa by scanning electron microscopy using orientation microscopy (EBSD). Radiation porosity with maximum void size up to 200 nm was observed in austenitic steel structure after neutron irradiation. Nonuniformity, related to mesostructural elements, such as general grain boundaries, special CSL boundaries Σ3 (twins), areas with high density of low-angle boundaries, is typical for radiation porosity.

Origin and Influence of Pre-Existing Segregation on Radiation-Induced Segregation In Austenitic Stainless Steels

1998 ◽  
Vol 540 ◽  
Author(s):  
E. A. Kenik ◽  
J. T. Busby ◽  
M. K. Miller ◽  
A. M. Thuvander ◽  
G. Was
Keyword(s):  
Electron Microscopy ◽  
Grain Boundaries ◽  
Stainless Steels ◽  
Analytical Electron Microscopy ◽  
Austenitic Stainless Steels ◽  
Atom Probe ◽  
Molecular Ions ◽  
Probe Field ◽  
Analytical Electron ◽  
Radiation Induced

AbstractThe pre-existing segregation at grain boundaries in two austenitic stainless steels has been investigated by atom probe field ion microscopy and analytical electron microscopy. In addition, the effect of radiation-induced segregation on the near-grain-boundary composition has been studied by analytical electron microscopy. Pre-existing enrichment of Cr, Mo, B, C and P and depletion of Fe and Ni near grain boundaries has been observed. Significant affinity between Mo and N in both alloys is indicated by the detection of MoN2+` molecular ions during field evaporation. The pre-existing segregation is modified by radiation-induced segregation resulting in Ni and Si enrichment near the boundary as well as depletion of chromium adjacent to the boundary resulting in a “W-shaped” Cr profile.

Grain Boundary Segregation and Irradiation-Assisted Stress Corrosion Cracking of Stainless Steels

1999 ◽  
Vol 5 (S2) ◽  
pp. 760-761
Author(s):  
E.A. Kenik ◽  
J.T. Busby ◽  
M.K. Miller ◽  
A.M. Thuvander ◽  
G. Was
Keyword(s):  
Stainless Steel ◽  
Grain Boundaries ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Stainless Steels ◽  
Elevated Temperatures ◽  
Boundary Segregation ◽  
Austenitic Stainless Steels ◽  
Corrosion Cracking ◽  
Radiation Induced

Irradiation-assisted stress corrosion cracking (IASCC) of irradiated austenitic stainless steels has been attributed to both microchemical (radiation-induced segregation (RIS)) and microstructural (radiation hardening) effects. The flux of radiation-induced point defects to grain boundaries results in the depletion of Cr and Mo and the enrichment of Ni, Si, and P at the boundaries. Similar to the association of stress corrosion cracking with the depletion of Cr and Mo in thermally sensitized stainless steels, IASCC is attributed in part to similar depletion by RIS. However, in specific heats of irradiated stainless steel, “W-shaped” Cr profiles have been observed with localized enrichment of Cr, Mo and P at grain boundaries. It has been show that such profiles arise from pre-existing segregation associated with intermediate rate cooling from elevated temperatures. However, the exact mechanism responsible for the pre-existing segregation has not been identified.Two commercial heats of stainless steel (304CP and 316CP) were forced air cooled from elevated temperatures (∽1100°C) to produce pre-existing segregation.

scholarly journals Exploring radiation induced segregation mechanisms at grain boundaries in equiatomic CoCrFeNiMn high entropy alloy under heavy ion irradiation

2018 ◽  
Vol 156 ◽  
pp. 80-84 ◽  
Author(s):  
Christopher M. Barr ◽  
James E. Nathaniel ◽  
Kinga A. Unocic ◽  
Junpeng Liu ◽  
Yong Zhang ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Ion Irradiation ◽  
Heavy Ion ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Heavy Ion Irradiation ◽  
Radiation Induced

Defect-Solute Interactions Near Irradiated Grain Boundaries

1993 ◽  
Vol 319 ◽  
Author(s):  
E. P. Simonen ◽  
J. S. Vetrano ◽  
H. L. Heinisch ◽  
S. M. Bruemmer
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Austenitic Stainless Steels ◽  
Back Diffusion ◽  
Metallic Materials ◽  
Grain Boundary Characteristics ◽  
Radiation Induced ◽  
Composition Profiles ◽  
Solute Interactions ◽  
Boundary Characteristics

AbstractDefect-solute interactions control radiation-induced segregation (RIS) to interfacial sinks, such as grain boundaries, in metallic materials. The best studied system in this regard has been austenitic stainless steels. Measurements of grain boundary composition indicate that RIS of major alloying elements is in reasonable agreement with inverse-Kirkendall predictions. The steep and narrow composition profiles are shown to result from limited back diffusion near the boundary. Subsequently, defect-solute interactions that affect the near-boundary defect concentrations strongly affect RIS. The variability in measured RIS may in part be caused by grain boundary characteristics.

Comparison Of Thermally- And Irradiation-Induced Grain Boundary Segregation In Austenitic Stainless Steels

1991 ◽  
Vol 238 ◽  
Author(s):  
Edward A. Kenik
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Stainless Steels ◽  
Analytical Electron Microscopy ◽  
Boundary Segregation ◽  
Austenitic Stainless Steels ◽  
Chromium Depletion ◽  
Thermal Sensitization ◽  
The Matrix ◽  
Radiation Induced

ABSTRACTSegregation at grain boundaries in austenitic stainless steels sensitized by either thermal annealing or irradiation was studied by analytical electron microscopy. Characterization of grain boundary compositions in both types of materials was performed by high spatial resolution (≥2 nm) X-ray microanalysis. Whereas similar chromium depletion is observed in both processes, there are differences in the behavior of the other alloying elements and in the mechanisms responsible for the segregation. In thermal sensitization, the nickel/iron ratio and the silicon level observed at grain boundaries are similar to those for the matrix. In cases where little or no precipitation occurs, co-segregation of phosphorus, chromium, and molybdenum occurs at boundaries and interfaces. For radiation sensitization, radiation-induced segregation (RIS) results in enrichment of nickel, silicon, and, in certain cases, phosphorus and in depletion of iron at grain boundaries. There appears to be some synergism between segregation of nickel and silicon, which increases the magnitude of RIS effects. Grain boundary precipitation is often observed in both thermally- and irradiation-sensitized materials. However, the nature and origins of the two types of precipitation are different. The formation of chromium-enriched grain boundary carbides is the cause of the chromium depletion in thermal sensitization. In contrast, the precipitates produced by irradiation are enriched in nickel and silicon and depleted in chromium relative to the matrix and therefore are the result of RIS. Results for thermal- and radiation-induced segregation in manganese-stabilized austenites are compared to that for nickel-stabilized austenites.

In situ TEM studies of irradiation effects for materials improvement

1991 ◽  
Vol 49 ◽  
pp. 452-453
Author(s):  
Charles W. Allen
Keyword(s):  
Nuclear Reactor ◽  
Austenitic Stainless Steels ◽  
High Energy ◽  
Point Of View ◽  
In Situ Tem ◽  
Irradiation Effects ◽  
Tem Analysis ◽  
Radiation Induced ◽  
Analytical Tools

Irradiation effects studies employing TEMs as analytical tools have been conducted for almost as many years as materials people have done TEM, motivated largely by materials needs for nuclear reactor development. Such studies have focussed on the behavior both of nuclear fuels and of materials for other reactor components which are subjected to radiation-induced degradation. Especially in the 1950s and 60s, post-irradiation TEM analysis may have been coupled to in situ (in reactor or in pile) experiments (e.g., irradiation-induced creep experiments of austenitic stainless steels). Although necessary from a technological point of view, such experiments are difficult to instrument (measure strain dynamically, e.g.) and control (temperature, e.g.) and require months or even years to perform in a nuclear reactor or in a spallation neutron source. Consequently, methods were sought for simulation of neutroninduced radiation damage of materials, the simulations employing other forms of radiation; in the case of metals and alloys, high energy electrons and high energy ions.

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