Matthew A. Steiner

Crystallographic texture of straight-rolled α-uranium foils via neutron and X-ray diffraction

The texture of recrystallized straight-rolled α-uranium foils, a component in prospective irradiation target designs for medical isotope production, has been measured by neutron diffraction, as well as X-ray diffraction using both Cu and Mo sources. Variations in the penetration depth of neutron and X-ray radiation allow for determination of both the bulk and surface textures. The bulk α-uranium foil texture is similar to the warm straight-rolled plate texture, with the addition of a notable splitting of the (001) poles along the transverse direction. The surface texture of the foils is similar to the bulk, with an additional (001) texture component that is oriented between the rolling and normal directions. Differences between the surface and bulk textures are expected to arise from shear forces during the rolling process and the influence that distinct strain histories have on subsequent texture evolution during recrystallization.

Predictive Sensitization Modeling for AA5xxx Aluminum Alloys Including Non-Isothermal Cases

Sensitization of marine grade AA5xxx aluminum alloys results from precipitation of the intermetallic β phase along grain boundaries and is typically assessed by the destructive ASTM G67 procedure. ...

Strain induced microstructural and ordering behaviors of epitaxial Fe38.5Pd61.5 films grown by pulsed laser deposition

Epitaxial films of Fe38.5Pd61.5 at the L10-L12 eutectoid composition have been grown on MgO (001) oriented substrates by pulsed laser deposition. The effect of deposition temperature on the magnetic, microstructural, and crystallographic natures of these films are discussed. The films in this study exhibit atomic ordering with increasing deposition temperature, transitioning from the disordered face centered cubic (FCC) phase to an L12 ordered phase, which is tetragonally distorted due to epitaxial strain. This distortion leads to a perturbation in the Fe occupancy of the Pd superlattice sites at nonstoichiometric compositions. Additionally, Fe38.5Pd61.5 films grown at 550 °C have been found in an unique two-phase microstructure of prismatic, Fe60Pd40 disordered FCC secondary phases with 10–100 nm facets oriented along the ⟨110⟩ substrate directions, embedded within a nearly stoichiometric ordered L12-Fe27Pd73 matrix. These secondary phase precipitates exhibit single domain magnetic axis rotation, while t...

The Relative Contributions of Deformation Modes to AZ31 Rolling Textures in Different Temperature Regimes

Key differences in the textures of cold-, warm-, and hot-rolled Mg alloy AZ31 sheets and plates are identified. It is shown that incorporation of compression twinning within Visco-Plastic Self-Consistent (VPSC) polycrystal plasticity simulations reproduces key features of the cold-rolling texture that have not previously been predicted. Discussion of recent observations of recrystallization and grain growth provide explanations for the hot-rolled texture. Finally, it is demonstrated that starting with the correct initial texture is essential to produce observed features in all the rolling textures, including warm-rolling.

Path length dependent neutron diffraction peak shifts observed during residual strain measurements in U–8 wt% Mo castings

This study reports an angular diffraction peak shift that scales linearly with the neutron beam path length traveled through a diffracting sample. This shift was observed in the context of mapping the residual stress state of a large U–8 wt% Mo casting, as well as during complementary measurements on a smaller casting of the same material. If uncorrected, this peak shift implies a non-physical level of residual stress. A hypothesis for the origin of this shift is presented, based upon non-ideal focusing of the neutron monochromator in combination with changes to the wavelength distribution reaching the detector due to factors such as attenuation. The magnitude of the shift is observed to vary linearly with the width of the diffraction peak reaching the detector. Consideration of this shift will be important for strain measurements requiring long path lengths through samples with significant attenuation. This effect can probably be reduced by selecting smaller voxel slit widths.

Constructing portable depth from defocus optical profilometers for surface roughness evaluation

Hand portability of non-contact optical profilometers represents a significant technological breakthrough for wide-area industrial processes such as grit blasting, capable of replacing mechanical styluses and providing real time assessment of surface roughness without damaging sampled areas. This paper demonstrates the possibility of building depth from defocus profilometers using off the shelf components, allowing for improved portability, affordability, and customization compared to similar table-top commercial products. An outlined demonstration device is proven to be capable of matching the performance of an ISO/NIST standardized mechanical profilometer for isotropic rough surfaces in the 2–10 μm Ra range with R2 > 0.96, and important considerations for each component of the assembly are addressed in detail. A prototype for a next generation liquid-lens based depth from defocus optical profilometer is also presented along with the technological obstacles found to be associated with such devices.

Matrix assisted growth of nanoparticles and nanoporous thin films: An emerging approach

Complex inorganic nanoparticles and nanoporous films have been synthesized by ultraviolet decomposition of metal based acetate precursors. Unary, alloyed and oxide crystalline nanoparticles where characterized via transmission electron microscopy.