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Dive into the research topics where R. D. Carter is active.

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Featured researches published by R. D. Carter.


Journal of Nuclear Materials | 1993

Effects of proton irradiation on the microstructure and microchemistry of type 304L stainless steel

R. D. Carter; D. L. Damcott; Michael Atzmon; Gary S. Was; E.A. Kenik

Abstract A research program has been undertaken to determine the origins of irradiation-assisted stress corrosion cracking (IASCC) in austenitic alloys in light water reactors, and the effect of impurities on IASCC susceptibility. Controlled purity alloys of 304L stainless steel were irradiated with protons at 400°C to a dose of 1 dpa and analyzed via Auger electron spectroscopy (AES) and scanning transmission electron microscopy (STEM). The alloys investigated were an ultra-high purity (UHP) alloy and UHP alloys containing phosphorus (UHP + P), sulfur (UHP + S), or silicon (UHP + Si). Microstructural and microchemical changes were quantified and compared with literature results for other irradiating species. Following irradiation, the alloys showed dislocation loop formation and growth, “black dot” loops, and a change in the nature of the dislocation network. AES and STEM microchemical analysis of the alloys revealed Cr depletion of up to 6 at% and Ni enrichment of up to 6.6 at% at the grain boundaries of the alloys, with more segregation observed in the alloys containing impurities than in the UHP alloy. Significant grain boundary enrichment of P and Si in the UHP + P and UHP + Si alloys, respectively, was also observed. The results of the analyses of proton-irradiated samples are shown to compare favorably with previous studies on samples irradiated with neutrons at or near LWR conditions.


Journal of Nuclear Materials | 1994

Quantitative analysis of radiation-induced grain-boundary segregation measurements

R. D. Carter; D. L. Damcott; Michael Atzmon; Gary S. Was; Stephen M. Bruemmer; E.A. Kenik

Radiation-induced and precipitation-induced grain-boundary segregation profiles are routinely measured by scanning-transmission electron microscopy using energy-dispersive X-ray spectroscopy (STEM-EDS). However, radiation-induced grain-boundary segregation (RI9 profiles achieved at low and moderate temperatures are e.xceedingly narrow, typically less than 10 nm full width at half maximum. Since the instrumental spatial resolution can be a significant fraction of this value, the determination of grain boundary compositions poses a formidable challenge. STEM-EDS and Auger electron spectroscopy @ES) measurements are reported, performed on controlled-purity alloys of type 304L stainless steel irradiated with 3.4 MeV protons to 1 displacement per atom at 400°C. Because of statistical noise and the practical lower limit on the step size in STEM, deconvolution of the measured data does not yield physical results. An alternative analysis of STEM data is presented. Numerical calculations of RIS profiles are convoluted with the instrumental broadening function and modified iteratively to fit the data, yielding a “best estimate” profile. This “best estimate” is convoluted with the Auger intensity profile to yield a simulated AES measurement, which is compared with the actual AES measurement to provide an independent test of the validity of the “best estimate”. For impurities with a narrow segregation profile and an Auger electron escape depth of one monolayer, a combination of STEM and AES data allows a determination of the width of the segregated layer. It is found that, in an ultrahigh-purity alloy doped with P, the latter is essentially contained in a single monolayer.


Journal of Nuclear Materials | 1993

Irradiation assisted stress corrosion cracking of controlled purity 304L stainless steels

J. M. Cookson; R. D. Carter; D. L. Damcott; Michael Atzmon; Gary S. Was

Abstract The effect of chromium, phosphorus, silicon and sulfur on the stress corrosion cracking of 304L stainless steel in CERT tests in high purity water or argon at 288°C following irradiation with 3.4 MeV protons at 400°C to 1 dpa, has been investigated using ultrahigh purity alloys (UHP) with controlled impurity additions. Grain boundary segregation of phosphorus or silicon due to proton irradiation was quantified using both Auger electron spectroscopy and scanning transmission electron microscopy, and the alloys with impurity element additions were observed to have greater grain boundary chromium depletion and nickel enrichment than the UHP alloy. The UHP alloy suffered severe cracking in CERT tests in water. Less cracking was found after CERT test of irradiated UHP+Por UHP+Si alloys, despite greater chromium depletion. This suggests a mitigating effect of phosphorus and silicon at grain boundaries. No cracking was found in argon tests, eliminating a purely mechanical embrittlement mechanism, but not eliminating a contribution from radiation hardening. Implanted hydrogen was not a factor in the intergranular cracking found.


Radiation Effects and Defects in Solids | 1991

Proton-induced grain boundary segregation in stainless steel

D. L. Damcott; J. M. Cookson; R. D. Carter; J. R. Martin; Michael Atzmon; Gary S. Was

Abstract A technique is developed which addresses the problem of irradiation assisted stress corrosion cracking of stainless steels in light water reactors using high energy protons to induce grain boundary segregation. These results represent the first grain boundary segregation measurements in bulk produced by proton irradiation of stainless steel. The technique allows the study of grain boundary composition with negligible sample activation, short irradiation time, rapid sample turnaround and at minimal cost. Scanning Auger electron microscopy is used to obtain grain boundary composition measurements of irradiated and unirradiated samples of ultra high purity (UHP) type 304L stainless steel and UHP type 304L steels with the additions of phosphorus (UHP + P) and sulphur (UHP + S). Results show that irradiation of all three alloys causes significant Ni segregation to the grain boundary and Cr and Fe away from it. Irradiation of the UHP + P alloy also results in segregation of P at the grain boundary from...


MRS Proceedings | 1996

Defect Microstructures and Deformation Mechanisms in Irradiated Austenitic Stainless Steels

S. M. Bruemmer; J. I. Cole; R. D. Carter; Gary S. Was

Microstructural evolution and deformation behavior of austenitic stainless steels are evaluated for neutron, heavy-ion and proton irradiated materials. Radiation hardening in austenitic stainless steels is shown to result from the evolution of small interstitial dislocation loops during lightwater-reactor (LWR) irradiation. Available data on stainless steels irradiated under LWR conditions have been analyzed and microstructural characteristics assessed for the critical fluence range (0.5 to 10 dpa) where irradiation-assisted stress corrosion cracking susceptibility is observed. Heavy-ion and proton irradiations are used to produce similar defect microstructures enabling the investigation of hardening and deformation mechanisms. Scanning electron, atomic force and transmission electron microscopies are employed to examine tensile test strain rate and temperature effects on deformation characteristics. Dislocation loop microstructures are found to promote inhomogeneous planar deformation within the matrix and regularly spaced steps at the surface during plastic deformation. Twinning is the dominant deformation mechanism at rapid strain rates and at low temperatures, while dislocation channeling is favored at slower strain rates and at higher temperatures. Both mechanisms produce highly localized deformation and large surface slip steps. Channeling, in particular, is capable of creating extensive dislocation pileups and high stresses at internal grain boundaries which may promote intergranular cracking.


MRS Proceedings | 1996

Dose Dependence of Radiation Induced Segregation in Proton Irradiated Austen1tic Alloys

J. T. Busby; Todd R. Allen; R. D. Carter; E.A. Kenik; Gary S. Was

The dose dependence of radiation-induced segregation (RIS) is investigated for proton irradiated ultra high-purity (UHP) 304L stainless steel and Fe-20Cr-24Ni. Grain boundary compositions were measured in samples irradiated with 3.2 MeV protons at 400°C to doses ranging from 0.1 to 3.0 dpa. RIS measurements were made using scanning transmission electron microscopy with energy dispersive x-ray spectroscopy (STEM/EDS) and compared to results from Auger electron spectroscopy (AES). Comparison of the dose dependence for HP-304L and Fe- 20Cr-24Ni shows that RIS is alloy specific. The approach to steady-state Cr depletion was observed to be more rapid in the alloy with higher Ni content. Fe-2OCr-24Ni reaches a steady-state Cr depletion level by 0.5 dpa, and the amount of Cr depletion in HP-304L SS is still increasing between 1.0 and 3.0 dpa. RIS in the stainless steel alloys irradiated with 3.2 MeV protons is comparable to that in neutron irradiated steels of similar composition.


Proceedings of the 6th International Symposium on Environmental Degradation of Materials in Nuclear Power Systems-Water Reactors | 1993

Radiation hardening effects on localized deformation and stress corrosion cracking of stainless steels

S.M. Bruemmer; J.I. Cole; R. D. Carter; G.S. Was


Proceedings of the 6th International Symposium on Environmental Degradation of Materials in Nuclear Power Systems-Water Reactors | 1993

Capabilities and limitations of analytical methods used to measure radiation-induced grain boundary segregation

R. D. Carter; D. L. Damcott; M. Atzmon; G. S. Was; S.M. Bruemmer; E. A. Kenik


Unknown Journal | 1995

Deformation mechanisms in a proton-irradiated austenitic stainless steel

R. D. Carter; M. Atzmon; G.S. Was; S.M. Bruemmer


Unknown Journal | 1997

Dose dependence of radiation induced segregation in proton irradiated austenitic alloys

J. T. Busby; T.R. Allen; R. D. Carter; E. A. Kenik; G. S. Was

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Gary S. Was

University of Michigan

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E.A. Kenik

Oak Ridge National Laboratory

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E. A. Kenik

University of Michigan

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J. T. Busby

University of Michigan

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S. M. Bruemmer

Pacific Northwest National Laboratory

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J. I. Cole

Pacific Northwest National Laboratory

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