Tarik A. Saleh

Intergranular Strain and Phase Transformation in a Cobalt-Based Superalloy

ULTIMET® alloy, a cobalt-based superalloy with good corrosion and wear resistant properties, exhibits a deformation-induced phase transformation from the face-centered-cubic (FCC) phase to the hexagonal-close-packed (HCP) phase. The HCP phase formation during monotonic tensile loading was investigated using in-situ neutron diffraction. The HCP phase is first observed at a stress level of 810 MPa, which is well beyond macroscopic yielding. Strain analysis is performed on the FCC phase diffraction data in order to relate the lattice-strain development with the evolution of the new HCP phase. A method of calculating the effective macroscopic stress associated with the measured lattice strains is presented here. The effective stress can then be compared to the applied macroscopic stress in order to draw conclusions about the load-partitioning behavior of the material as a new phase develops.

Elastic moduli of

We study the time evolution (aging) of the elastic moduli of an eight-year-old polycrystalline δ-Pu 2.0 at. % Ga alloy (δ-Pu:Ga) at different fixed temperatures from 295 K to nearly 500 K in real time using Resonant Ultrasound Spectroscopy. After 8 years of aging at 295 K, the bulk and shear moduli increase at a normalized rate of 0.2%/year and 0.6%/year, respectively. As the temperature is raised, two time dependences are observed, an exponential one of about a week, followed by a linear one (constant rate). The linear rate is thermally activated with an activation energy of 0.33 + 0.06 eV. Above 420 K a qualitative change in the time evolution is observed; the bulk modulus decreases with time while the shear modulus continues to stiffen. No change in the behavior of the time evolution is observed as the α−β transition temperature is crossed as would be expected if a decomposition of δ-Pu:Ga to α-Pu and Pu3Ga occurred over the temperature range studied. Our results indicate that the main mechanism of agi...

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A variety of tensile samples of Ferritic and Oxide Dispersion Strengthened (ODS or nanostructured ferritic) steels were placed the ATR reactor over 2 years achieving doses of roughly 4-6 dpa at temperatures of roughly 290°C. Samples were shipped to Wing 9 in the CMR facility at Los Alamos National Laboratory and imaged then tested in tension. This report summarizes the room temperature tensile tests, the elevated temperature tensile tests (300°C) and fractography and reduction of area calculations on those samples. Additionally small samples were cut from the undeformed grip section of these tensile samples and sent to the NSLS synchrotron for high energy X-ray analysis, initial results will be described here.

-Pu239 reveal aging in real time

A variety of tensile samples of Ferritic and Oxide Dispersion Strengthened (ODS or nanoferritic) steels were placed the ATR reactor over 2 Years achieving doses of roughly 4-6 dpa at temperatures of roughly 290°C. After irradiation, samples were shipped from the MFC hot cells at Idaho National Laboratory (INL) to the Wing 9 hot cells in the CMR facility at Los Alamos National Laboratory. Samples were cleaned to removed alpha contamination from the MFC hot cells, and then, as needed removed from their irradiation containers, sorted and inspected. This report will summarize the inspection of the Disc Multipurpose Coupon (DMC) inspection from packet 7-1.

High Temperature Mechanical Properties, Fractography and Synchrotron Studies of ATF clad materials from the UCSB-NSUF Irradiations.

Resonant ultrasound spectroscopy (RUS) is a well-established method for determination of the full tensor of elastic moduli of a solid sample in a single frequency sweep. The elastic moduli, together with density, can provide information related to materials fabrication processes, providing a unique signature, or fingerprint, of a material. The goal of this study was to provide forensics for nuclear materials in solid ceramic or metallic form, including composition. The premise of this study was that it is really difficult to find two materials whose density and shear and /or bulk modulus match. We used RUS to determine the bulk and shear modulus for a total of 27 samples. The samples consisted of depleted uranium oxide (MOX) with different doping of Ce, Pu, and Nd oxides, and different methods of fabrication. They were in form of cylinders with flat and parallel faces. Two-dimensional and three-dimensional spaces were investigated, using shear modulus, bulk modulus, and density as variables. The densities...