Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 18 of 18 for “"Surface melting"”.
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Evaluation of laser surface melting to mitigate chloride stress corrosion cracking in an austenitic stainless steel
This thesis evaluates the ability of laser surface melting to mitigate chloride stress corrosion cracking (See) of type 304 stainless steel. The effects of laser surface melting on microstructure, mechanical state, and corrosion behavior were examined. The major effect of laser surface melting of …
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Laser and electron beam treatments for corrosion protection of friction stir welds in aerospace alloys
… treatments are required. A pre-weld treatment of surface preparation was required to ensure a weld with good mechanical properties. The surface preparation necessary is the removal of paint and anodising layers from aerospace alloys. Laser paint removal was assessed and designed to remove these …
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Microstructures and Properties of Rapidly Solidified Aluminum Alloys
… alloys that had been rapidly solidified by laser surface melting (LSM) or chill block melt spinning (CBMS). The alloys, all of which had the same solute content, had the composition Al-4.1Fe-0.6X (at.%), where X was Mo, Ce, Cr, V, or Zr. A binary Al-4.7Fe (at.%) was used for comparison.
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Dynamic Compaction of Rapidly Solidified Nickel-Base Superalloys (Rapid Solidification, Powder Metallurgy, Hot Isostatic Pressing, Consolidation, Precipitation)
… atomization, chill-block melt-spinning and laser surface melting. Transmission electron microscopy was utilized to characterize the various microstructures obtained in terms of growth morphology, segregation profiles, (gamma)' size and distribution of secondary hardening phases. The response of …
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Understanding surface and sub-surface phenomena in nickel-based superalloy castings
… results in scrapped components. Internal surface melting was found on intermediate pressure turbine blades following high-temperature heat-treatment; it consists of a layer enriched in aluminium and tantalum on the surface of the internal cooling passage. The discovery led to a systematic …
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Anode Materials for High Power Microwave Devices
… this, two methods have been identified: laser surface melting for outgassing reduction and laser surface structuring for secondary electron emission reduction. Localised laser surface melting allows controlled grain nucleation, grain size increase and shaping, to create a hydrogen atom …
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A Microstructural Characterization of as-Cast and Rapidly Solidified Titanium-Silicon Alloys (Silicide, Melt-Spinning, Precipitation, Metastable, Oxygen)
… rapidly solidified material, namely laser surface melting and melt-spinning. Prior to RS, a careful microstructural characterization of the as-cast material was undertaken. This also involved a study of an homogenized and heat treated base alloy (Ti-2 wt%Si) to determine the types of …
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Mechanics, mechanisms, and modeling of the chemical mechanical polishing process
… of polishing - microcutting, brittle fracture, surface melting and burnishing - are reviewed. Blanket wafers coated with a wide range of materials are polished to verify the models. Plastic deformation is identified as the dominant mechanism of material removal in fine abrasive polishing.
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Laser Annealing of Ion Implanted Silicon
… experimental investigation of the dynamics of surface melting and regrowth and electrical activation of Si('+) and BF(,2)('+) ion implanted amorphized silicon annealed with a Q-switched Nd:glass laser ((lamda)= 1.06 (mu)m). In the theoretical calculations we have used the technique of finite …
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3 dimensional flow and thermal modelling of the friction stir welding process
… investigation into the evidence for and against surface melting during Friction Stir Welding. While microstructural evidence indicates that surface melting does not occur, some temperature measurements suggest otherwise. A balanced review is presented. It is believed that more data is required …
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Evidence for the Drainage of a Superglacial Lake as the Source of Seismic Waves Recorded at a Regional Distance
<p>Surface melting during the summer leads to the formation of lakes on the Greenland Ice Sheet surface, known as supraglacial lakes. Some of these lakes drain through cracks in their beds and release the water into the ice sheet. Previous studies suggest that some of the water reaches the bedrock, …
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Path integral Monte Carlo simulations of solid H2 surfaces and thin 4He films on H2 substrates
… We find evidence of quantum exchange in surface terraces for up to 1K. Second, the melting of the H$\sb2$ surface between 3 and 15K is examined since this is the cleanest example of quantum surface melting. Third, atomically thin superfluid $\sp4$He films on H$\sb2$ surfaces are …
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Submarine Geomorphology of the Continental Shelves of Southeast and Southwest Greenland from Olex Data
… deglaciation was characterised predominantly by surface melting.
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Modeling the impact of atmospheric moisture transport on global ice volume
… flux of moisture, whereas precession governs surface melting by regulating summer temperatures. The response of the ice sheet to obliquity and precession is comparable, and significantly smaller than what is observed in the oxygen isotope record of the late Pliocene and early Pleistocene (2.7 …
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Transport mechanisms and wetting dynamics in molecularly thin films of long-chain alkanes at solid/vapour interface : relation to the solid-liquid phase transition
… phase transitions. Immediately above the bulk melting temperature the alkanes wet partially the surface (drops). In this temperature range the substrate surface is covered with a molecularly thin ordered, solid-like alkane film ("surface freezing"). Thus, the alkane melt wets its own solid only …
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Effects of Laser Shock Peening on Residual Stress, Texture and Deformation Microstructure of Ti-6Al-4V Alloy
Laser shock peening (LSP) is a novel surface treatment process that generates deep compressive residual stresses and microstructural changes and thereby dramatically improves fatigue strength of critical metal aircraft engine parts. In the past, researchers have evaluated the mechanical effects of …
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Effect of Laser Induced Crystallinity Modification on Degradation and Drug Release of Biodegradable Polymer
… irradiation is used in this study to induce surface melting and resolidification. The high cooling rate of the laser treatment coupled with the slow polymer crystallization kinetics leads to reduced surface crystallinity after the laser irradiation. Effects of laser irradiation on the surface …
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Télédétection micro-onde de surfaces enneigées en milieu arctique : étude des processus de surface de la calotte glaciaire Barnes, Nunavut, Canada
… sea level rise, a better characterisation of the surface processes such as the evolution of the surface mass balance is needed. This knowledge is currently very limited, mainly due to the sparse covering of automatic weather stations or in-situ measurements over the Arctic. Furthermore, several …