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On the Problem of Stress Corrosion

Description: "The object of the present work is first to investigate accurately the processes during stress corrosion, in particular, for light metal alloys and, as the first part of the investigation, to determine its laws; and secondly to explain its causes for various alloys and thereby find means for its partial or complete elimination and thus make possible the production of light metal alloys free from any stress corrosion. In the present paper some of the results of the investigation are given and the fundamental problems of stress corrosion discussed" (p. 1).
Date: July 1946
Creator: Graf, L.
Partner: UNT Libraries Government Documents Department

De-alloying and stress corrosion cracking. Final report, July 1, 1990--June 30, 1993

Description: Results of work on fracture properties of porous dealloyed gold structures indicates that this material undergoes a brittle-ductile transition as the size scale of the porosity increases. Aspects of the work reported on and proposed address fundamental issues related corrosion in alloy systems. De-alloyed film induce brittle fracture experiments are being performed on Ag-Au and Cu-Au alloy thin sheets. An indirect potential drop technique is being developed to measure dynamic crack motion. Preliminary work is being performed to determine optimum conditions for film thickness-crack penetration experiments.
Date: April 1, 1996
Creator: Sieradzki, K.
Partner: UNT Libraries Government Documents Department

Implications of early stages in the growth of stress corrosion cracking on component reliability

Description: Environment-induced crack growth generally progresses through several stages prior to component failure. Crack initiation, short crack growth, and stage 1 growth are early stages in crack development that are summarized in this paper. The implications of these stages on component reliability, derive from the extended time that the crack exists in the early stages because crack velocity is slow. The duration of the early stages provides a greater opportunity for corrective action if cracks can be detected. Several important factors about the value of understanding short crack behavior include: (1) life prediction requires a knowledge of the total life cycle of the crack including the early stages, (2) greater reliability is possible if the transition between short and long crack behavior is known component life after this transition is short and (3) remedial actions are more effective for short than long cracks.
Date: April 1, 1995
Creator: Jones, R.H. & Simonen, E.P.
Partner: UNT Libraries Government Documents Department

An Investigation of the Mechanism of IGA/SCC of Alloy 500 in Corrosion Accelerating Heated Crevice Environments. Technical progress report

Description: OAK-B135 An Investigation of the Mechanism of IGA/SCC of Alloy 500 in Corrosion Accelerating Heated Crevice Environments. Technical progress report Note: This report was submitted electronically even though Part II A indicates by ''PAPER''.
Date: March 1, 2000
Creator: Lumsden, Jesse
Partner: UNT Libraries Government Documents Department

Stress corrosion cracking behavior of Alloy 600 in high temperature water

Description: SCC susceptibility of Alloy 600 in deaerated water at 360 C (statically loaded U-bend specimens) is dependent on microstructure and whether the material was cold-worked and annealed (CWA) or hot-worked and annealed (HWA). All cracking was intergranular, and materials lacking grain boundary carbides were most susceptible to SCC initiation. CWA tubing materials are more susceptible to SCC initiation than HWA ring-rolled forging materials with similar microstructures (optical metallography). In CWA tubing materials, one crack dominated and grew to a visible size. HWA materials with a low hot-working finishing temperature (<925 C) and final anneals at 1010-1065 C developed both large cracks (similar to those in CWA materials) and small intergranular microcracks detectable only by destructive metallography. HWA materials with a high hot-working finishing temperature (>980 C) and a high-temperature final anneal (>1040 C), with grain boundaries that are fully decorated, developed only microcracks in all specimens. These materials did not develop large, visually detectable cracks, even after more than 300 weeks exposure. A low-temperature thermal treatment (610 C for 7h), which reduces or eliminates SCC in Alloy 600, did not eliminate microcrack formation in high temperature processed HWA materials. Conventional metallographic and analytical electron microscopy (AEM) were done on selected materials to identify the factors responsible for the observed differences in cracking behavior. Major difference between high-temperature HWA and low-temperature HWA and CWA materials was that the high temperature processing and final annealing produced predominantly ``semi-continuous`` dendritic M{sub 7}C{sub 3} carbides along grain boundaries with a minimal amount of intragranular carbides. Lower temperature processing produced intragranular M7C3 carbides, with less intergranular carbides.
Date: July 1, 1995
Creator: Webb, G.L. & Burke, M.G.
Partner: UNT Libraries Government Documents Department

Some Observations on Stress-Corrosion Cracking of Single Crystals of AZ61X Magnesium Alloy

Description: Note presenting exploratory tests of the stress-corrosion cracking of single crystals of solution-treated AZ61X magnesium alloy in distilled water, in hydrofluoric acid, and in a salt-chromate solution. The results of this paper show that failures often start and run on planes other than the basal plane and are inconsistent with previously generated hypotheses. Results regarding the pilot tests on polycrystalline specimens and single-crystal tests are provided.
Date: July 1957
Creator: Meller, F. & Metzger, M.
Partner: UNT Libraries Government Documents Department

Environment-assisted-cracking under measured and/or controlled ectrochemical potential

Description: Longer-term stress corrosion cracking (SCC) experiments, described in the activity plan E-20-56, are well underway at LLNL to evaluate the SCC susceptibility of candidate corrosion-resistant inner container materials in a 90°ºC acidic brine containing 5 weight percent (wt%) NaCl using fatigue-precracked wedge-loaded double-cantilever-beam (DCB) specimens. The results of a recent localized corrosion study have revealed that the propensity to pitting and crevice corrosion in susceptible alloys is characterized by "critical potentials" obtained from the cyclic potentiodynamic polarization (CPP) experiments described in the activity plan E-20-43/44. It is also well known that the tendency to SCC can be influenced by the electrochemical potential. But the role of electrochemistry in SCC has not been explored to a large extent. Therefore, the proposed activity is aimed at evaluating the SCC behavior of susceptible container materials under measured and/or controlled electrochemical potential in repository-relevant environments using DCB and slow-strain-rate (SSR) test specimens. The magnitude of the controlled potential will be selected based on the measured "critical potentials" obtained from the CPP experiment performed earlier in a similar environment. The resultant data will enable the mechanistic understanding of the cracking process in materials of interest under the synergistic influence of applied stress and corrosive medium, which will be utilized in developing and validating the SCC models for long-term performance assessment.
Date: November 7, 1997
Creator: Roy, A.
Partner: UNT Libraries Government Documents Department

Stress corrosion cracking tests using double-cantilever-beam specimens

Description: Although a wide variety of degradation modes can occur in aqueous environments for corrosion-resistant metallic materials, localized corrosion such as pitting corrosion, crevice corrosion, SCC, and hydrogen embrinlement (HE) is considered to be the primary mode. The evaluation of the susceptibility of candidate corrosion-resistant container materials to pitting and crevice corrosion is well underway using electrochemical polarization techniques described in the Activity Plan E-20-43144. The proposed activity (E-20-56) is aimed at evaluating the SCC behavior of these materials in susceptible environments using the linearelastic-fracture-mechanics (LEFM) concept. The mechanical driving force for crack growth, or the stress distribution at the crack tip is quantified by the stress intensity factor, K, for the specific crack and loading geometry. The critical stress intensity factor for SCC, K<sub>ISCC</sub> for candidate materials will be evaluated in environments of interest, and their comparisons will be made to select the waste package inner container material having an optimum SCC resistance.
Date: October 25, 1996
Creator: Roy, A.
Partner: UNT Libraries Government Documents Department

Influence of Exposed Area on Stress-Corrosion Cracking of 24S Aluminum Alloy

Description: Note presenting results of a study of the area effect in 24S aluminum alloy. The area effect refers to the phenomenon whereby small areas show long times to failure while large areas show short times. The effects of stress level, degree of sensitivity of the alloy, and hydrogen peroxide concentration in the corrosion medium were studied.
Date: November 1954
Creator: Colner, William H. & Francis, Howard T.
Partner: UNT Libraries Government Documents Department

Stress-corrosion fatigue-crack growth in a Zr-based bulk amorphousmetal

Description: Electrochemical and mechanical experiments were conducted to analyze the environmentally-influenced cracking behavior of a bulk amorphous metal, Zr41.2Ti13.8Cu12.5Ni10Be22.5. This study was motivated by a scientific interest in mechanisms of fatigue-crack propagation in an amorphous metal, and by a practical interest in the use of this amorphous metal in applications that take advantage of its unique properties, including high specific strength, large elastic strains and low damping. The objective of the work was to determine the rate and mechanisms of subcritical crack growth in this metallic glass in an aggressive environment. Specifically, fatigue-crack propagation behavior was investigated at a range of stress intensities in air and aqueous salt solutions by examining the effects of loading cycle, stress-intensity range, solution concentration, anion identity, solution de-aeration, and bulk electrochemical potential. Results indicate that crack growth in aqueous solution in this alloy is driven by a stress-assisted anodic reaction at the crack tip. Rate-determining steps for such behavior are reasoned to be electrochemical, stress-dependent reaction at near-threshold levels, and mass transport at higher (steady-state) growth rates.
Date: September 21, 2005
Creator: Schroeder, V. & Ritchie, R. O.
Partner: UNT Libraries Government Documents Department

Hanford double shell tank corrosion monitoring instrument tree prototype

Description: High-level nuclear wastes at the Hanford site are stored underground in carbon steel double-shell and single-shell tanks (DSTs and SSTs). The installation of a prototype corrosion monitoring instrument tree into DST 241-A-101 was completed in December 1995. The instrument tree has the ability to detect and discriminate between uniform corrosion, pitting, and stress corrosion cracking (SCC) through the use of electrochemical noise measurements and a unique stressed element, three-electrode probe. The tree itself is constructed of AISI 304L stainless steel (UNS S30403), with probes in the vapor space, vapor/liquid interface and liquid. Successful development of these trees will allow their application to single shell tanks and the transfer of technology to other US Department of Energy (DOE) sites. Keywords: Hanford, radioactive waste, high-level waste tanks, electrochemical noise, probes, double-shell tanks, single-shell tanks, corrosion.
Date: November 1, 1995
Creator: Nelson, J.L.; Edgemon, G.L. & Ohl, P.C.
Partner: UNT Libraries Government Documents Department

Modeling of stress distributions on the microstructural level in Alloy 600

Description: Stress distribution in a random polycrystalline material (Alloy 600) was studied using a topologically correct microstructural model. Distributions of von Mises and hydrostatic stresses at the grain vertices, which could be important in intergranular stress corrosion cracking, were analyzed as functions of microstructure, grain orientations and loading conditions. Grain size, shape, and orientation had a more pronounced effect on stress distribution than loading conditions. At grain vertices the stress concentration factor was higher for hydrostatic stress (1.7) than for von Mises stress (1.5). The stress/strain distribution in the volume (grain interiors) is a normal distribution and does not depend on the location of the studied material volume i.e., surface vs/bulk. The analysis of stress distribution in the volume showed the von Mises stress concentration of 1.75 and stress concentration of 2.2 for the hydrostatic pressure. The observed stress concentration is high enough to cause localized plastic microdeformation, even when the polycrystalline aggregate is in the macroscopic elastic regime. Modeling of stresses and strains in polycrystalline materials can identify the microstructures (grain size distributions, texture) intrinsically susceptible to stress/strain concentrations and justify the correctness of applied stress state during the stress corrosion cracking tests. Also, it supplies the information necessary to formulate the local failure criteria and interpret of nondestructive stress measurements.
Date: April 1995
Creator: Kozaczek, K. J.; Petrovic, B. G.; Ruud, C. O. & Mcllree, A. R.
Partner: UNT Libraries Government Documents Department

Modeling of stresses at grain boundaries with respect to occurrence of stress corrosion cracking

Description: The distributions of elastic stresses/strains in the grain boundary regions were studied by the analytical and the finite element models. The grain boundaries represent the sites where stress concentration occurs as a result of discontinuity of elastic properties across the grain boundary and the presence of second phase particles elastically different from the surrounding matrix grains. A quantitative analysis of those stresses for steels and nickel based alloys showed that the stress concentrations in the grain boundary regions are high enough to cause a local microplastic deformation even when the material is in the macroscopic elastic regime. The stress redistribution as a result of such a plastic deformation was discussed.
Date: December 31, 1995
Creator: Kozaczek, K. J.; Sinharoy, A.; Ruud, C. O. & McIlree, A. R.
Partner: UNT Libraries Government Documents Department

Stress Corrosion Crack Detection on HU-25 Guardian Aircraft

Description: Several ultrasonic inspection methods were developed at the Federal Aviation Administration's Airworthiness Assurance NDI Validation Center (AANC) to easily and rapidly detect hidden stress corrosion cracks in all vertical windshield posts on the US Coast Guard (USCG) HU-25 Guardian aircraft. The inspection procedure locates cracks as small as 2.0 millimeters emanating from internal fastener holes and determines their length. A test procedure was developed and a baseline assessment of the USCG fleet was conducted. Inspection results on twenty-five aircraft revealed a good correlation with results made during subsequent structural disassembly and visual inspection.
Date: February 17, 1999
Creator: Blackmon, R.; Huffman, J.; Mello, C.W.; Moore, D.G. & Walkington, P.D.
Partner: UNT Libraries Government Documents Department

Inhibition of stress corrosion cracking of Alloy X-750 by prestrain

Description: Tests of precracked and as-notched compact tension specimens were conducted in 3600C hydrogenated water to determine the effect of prestrain on the stress corrosion cracking (SCC) resistance of Alloy X-750 in the HTH, AH and HOA heat treated conditions. Prestraining is defined as the intentional application of an initial load (or strain) that is higher than the final test load. Prestrain was varied from 10% to 40% (i.e., the initial to final load ratios ranged from 1.1 to 1.4). Other variables included notch root radius, stress level and irradiation. Specimens were bolt-loaded to maintain essentially constant displacement conditions during the course of the test. The frequent heat up and cooldown cycles that were necessary for periodic inspections provided an opportunity to evaluate the effect of test variables on rapid low temperature crack propagation to which this alloy is subject. For Condition HTH, application of 20% to 40% prestrain either eliminates or significantly retards SCC initiation in as-notched specimens and the onset of crack growth in precracked specimens. In addition, this procedure reduces the propensity for low temperature crack growth during cooldown. Similar results were observed for precracked HOA specimens. Application of 20% prestrain also retards SCC in as-notched and precracked AH specimens, but the effects are not as great as in Condition HTH. Prestraining at the 10% level was found to produce an inconsistent benefit. In-reactor SCC testing shows that prestrain greatly improves the in-flux and out-of-flux SCC resistance of Condition HTH material. No SCC was observed in precracked specimens prestrained 30%, whereas extensive cracking was observed in their nonprestrain counterparts.
Date: March 1, 1997
Creator: Mills, W.J.; Lebo, M.R. & Kearns, J.J.
Partner: UNT Libraries Government Documents Department

Stress corrosion cracking behavior of irradiated model austenitic stainless steel alloys.

Description: Slow-strain-rate tensile tests (SSRTs) and posttest fractographic analyses by scanning electron microscopy were conducted on 16 austenitic stainless steel (SS) alloys that were irradiated at 289 C in He. After irradiation to {approx}0.3 x 10{sup 21} n{center_dot}cm{sup {minus}2} and {approx}0.9 x 10{sup 21} n{center_dot}cm{sup {minus}2} (E &gt;1 MeV), significant heat-to-heat variations in the degree of intergranular and transgranular stress corrosion cracking (IGSCC and TGSCC) were observed. Following irradiation to a fluence of {approx}0.3 x 10{sup 21} n{center_dot}cm{sup {minus}2}, a high-purity laboratory heat of Type 316L SS (Si {approx} 0.024 wt%) exhibited the highest susceptibility to IGSCC. The other 15 alloys exhibited negligible susceptibility to IGSCC at this low fluence. The percentage of TGSCC on the fracture surfaces of SSRT specimens of the 16 alloys at {approx}0.3 x 10{sup 21} n{center_dot}cm{sup {minus}2} (E &gt; 1 MeV) could be correlated well with N and Si concentrations; all alloys that contained &lt;0.01 wt.% N and &lt;1.0 wt. % Si were susceptible, whereas all alloys that contained &gt;0.01 wt.% N or &gt;1.0 wt.% Si were relatively resistant. High concentrations of Cr were beneficial. Alloys that contain &lt;15.5 wt.% Cr exhibited greater percentages of TGSCC and IGSCC than those alloys with {approx}18 wt.% Cr, whereas an alloy that contains &gt;21 wt.% Cr exhibited less susceptibility than the lower-Cr alloys under similar conditions.
Date: July 16, 1999
Creator: Chung, H. M.; Karlsen, T. M.; Ruther, W. E.; Shack, W. J. & Strain, R. V.
Partner: UNT Libraries Government Documents Department

Computer Simulation of Intergranular Stress Corrosion Cracking via Hydrogen Embrittlement

Description: Computer simulation has been applied to the investigation of intergranular stress corrosion cracking in Ni-based alloys based on a hydrogen embrittlement mechanism. The simulation employs computational modules that address (a) transport and reactions of aqueous species giving rise to hydrogen generation at the liquid-metal interface, (b) solid state transport of hydrogen via intergranular and transgranular diffusion pathways, and (c) fracture due to the embrittlement of metallic bonds by hydrogen. A key focus of the computational model development has been the role of materials microstructure (precipitate particles and grain boundaries) on hydrogen transport and embrittlement. Simulation results reveal that intergranular fracture is enhanced as grain boundaries are weakened and that microstructures with grains elongated perpendicular to the stress axis are more susceptible to cracking. The presence of intergranular precipitates may be expected to either enhance or impede cracking depending on the relative distribution of hydrogen between the grain boundaries and the precipitate-matrix interfaces. Calculations of hydrogen outgassing and in gassing demonstrate a strong effect of charging method on the fracture behavior.
Date: April 1, 2000
Creator: Smith, R.W.
Partner: UNT Libraries Government Documents Department