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Approved for Public Release; Distribution is Unlimited / Friction Stir Processing (FSP), although relatively simple in concept, results in an extremely complex thermomechanical treatment to the material being processed. Previous studies of FSP have shown that the process results in extremely high strain, strain rates and temperatures as well as gradients in strain, strain rate and temperature within a small volume of material. This thesis will study the effect of varying FSP parameters during the processing of Nickel-Aluminum-Bronze (NAB) propeller material. The modeling program CTH was used to define the relationship between tool rotation speed, traversing speed and the total power input to the material. The tool's mechanical power and the power generated by deformation of the material has been investigated. The modeling experiments were designed to gain an understanding of the relationship of process parameters, microstructure and mechanical properties, and to enhance our understanding of the flow patterns and thermal histories of the NAB material in the stir zone. / Lieutenant, United States Navy

Ni-based superalloys are used for high-temperature components of gas turbines in both industrial and aerospace applications due to their ability to maintain dimensional stability under conditions of high stress and strain. The oxidation resistance of these alloys often dictates their service lifetime. This study focuses on the isothermal oxidation behaviour of three nickel-based superalloys; namely, polycrystalline cast IN738LC, single-crystal N5 and a ternary Ni-Fe-Cr (TAS) powder metallurgy alloy. The isothermal oxidation tests were conducted at 900°C in the static air up to 1000h and the specific aspects studied were the oxidation behaviour of these chromia-forming and alumina-forming alloys that are used extensively in industry. In particular, the behaviour of oxide scale growth and subsurface changes were analysed in detail using various techniques such as SEM, EDS and AFM. From the isothermal oxidation kinetics, the oxidation rate constant, kp was calculated for each alloy and found to be; kp = 2.79 x 10-6 mg2.cm-4.s-1 for IN738LC, kp = 1.42 x 10-7 mg2.cm-4.s-1 for N5 and kp = 1.64 x 10-7 mg2.cm-4.s-1 for TAS. Based on a microstructural analysis, IN738LC exhibited a continuous dense outer scale of Cr2O3 and discontinuous inner scale of Al2O3, whereas N5 and TAS showed a dense outer scale of Al2O3 alone. The results suggested that the N5 and PM-TAS alloys are more oxidation resistant than the IN738LC under these conditions. / October 2016

by Kwok Shu Cheung, Eric. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1990. / Bibliography: leaves 89-106. / Acknowledgement --- p.i / Abstract --- p.ii / Introduction / Chapter A. --- Objective --- p.1 / Chapter B. --- Literature Review / Chapter 1. --- Electroplating industry in Hong Kong and its impact on the environment --- p.7 / Chapter 2. --- Physical and chemical methods for removing heavy metals from electroplating effluent --- p.11 / Chapter 3. --- Removal of heavy metals by conventional activated sludge process --- p.16 / Chapter 4. --- Acclimation of wastewater bacteria to heavy metals --- p.26 / Chapter 5. --- Biosorbent and its role in metal detoxification --- p.28 / Materials and Methods / Chapter A. --- Isolation and selection of nickel-resistant bacteria --- p.32 / Chapter B. --- Culture medium and solution --- p.33 / Chapter C. --- Growth of organism --- p.33 / Chapter D. --- Immobilization of bacterial cells --- p.36 / Chapter E. --- Effect of growth conditions on nickel removal capacity of immobilized Enterobacter sp. cells --- p.37 / Chapter F. --- Effect of bioreactor operational conditions on the Ni2+ removal capacity of immobilized bacterial cells --- p.38 / Chapter G. --- Optimization of nickel removal efficiency of bioreactor --- p.39 / Chapter H. --- Determination of Ni2+ adsorption isotherm of immobilized cells of Enterobacter sp. --- p.39 / Chapter I. --- Recovery of nickel from the bioreactor --- p.40 / Chapter J. --- Activity of the regenerated bioreactor --- p.41 / Chapter K. --- Removal of Ni2+ from synthetic effluent by bioreactor --- p.41 / Chapter L. --- Removal of Ni2+ from electroplating effluent by bioreactor. --- p.41 / Chapter M. --- Production of immobilized bacterial cells by replacement of D-glucose by molasses in the growth medium --- p.42 / Results / Chapter A. --- Isolation and selection of nickel resistant bacteria --- p.44 / Chapter B. --- Effect of growth conditions on nickel removal capacity of immobilized Enterobacter sp. cells / Chapter 1. --- Nutrient limitation --- p.44 / Chapter 2. --- D-glucose concentration --- p.45 / Chapter 3. --- Incubation temperature and incubation time --- p.45 / Chapter C. --- Heavy metal removal capacity of immobilized cells of Enterobacter sp. --- p.50 / Chapter D. --- Effect of bioreactor operational conditions on Ni2+ removal capacity of the immobilized bacterial cells --- p.50 / Chapter E. --- Optimization of nickel removal efficiency of bioreactor --- p.55 / Chapter F. --- Determination of Ni2+ adsorption isotherm of immobilized cells of Enterobacter --- p.57 / Chapter G. --- Recovery of nickel from the bioreactor and activity of regenerated bioreactor against a fresh nickel flow --- p.61 / Chapter H. --- Removal of Ni2+ from synthetic effluent by bioreactor --- p.61 / Chapter I. --- Removal of Ni2+ from electroplating effluent by bioreactor. --- p.64 / Chapter J. --- Production of immobilized bacterial cells by replacement of D-glucose by molasses in the growth medium --- p.68 / Discussions / Chapter A. --- Effect of growth conditions on nickel removal capacity of immobilized Enterobacter sp. cells --- p.70 / Chapter B. --- Heavy metal removal capacity of immobilized cells of Enterobacter sp. --- p.73 / Chapter C. --- Effect of bioreactor operational conditions on Ni2+ removal capacity of the immobilized bacterial cells --- p.74 / Chapter D. --- Optimization of nickel removal efficiency of bioreactor --- p.74 / Chapter E. --- Determination of Ni2+ adsorption isotherm of immobilized cells of Enterobacter sp. --- p.76 / Chapter F. --- Recovery of nickel from the bioreactor and activity of the regenerated bioreactor against a fresh nickel flow --- p.77 / Chapter G. --- Removal of Ni2+ from synthetic effluent by bioreactor --- p.78 / Chapter H. --- Removal of Ni2+ from electroplating effluent by bioreactor --- p.79 / Chapter I. --- Production of immobilized bacterial cells by replacement of D-glucose by molasses in the growth medium --- p.82 / Chapter J. --- Further considerations of applicability of immobilized Enterobacter sp. cells to treatment of electroplating effluent --- p.83 / Conclusions --- p.86 / References --- p.89

A thermally grown oxide (TGO) such as the alumina scale formed on a bondcoat enhances the oxidation and corrosion resistance of thermal barrier coating (TBC)- bondcoat-superalloy substrate systems. As the external alumina scale lies between the thermal barrier coating and bondcoat, its first spallation and subsequent TBC delamination become critical. Once the external alumina scale spalls, it will spall together with the TBC, leaving the system with no temperature barrier protection. Operational factors such as thermal cycling conditions, water vapour in the oxidation atmosphere, and alloying elements comprising the bondcoat system affect alumina scale adherence. Another problem that arises for the majority of bondcoat systems, β (Ni,Pt)Al and MCrAlY (M=Metal), are rich in aluminium. This causes aluminium to diffuse into the substrate, enriching it with aluminium during service, transforming phases in the substrate alloying system. The purpose of this study was to develop bondcoat materials that promote formation of a strongly adherent TGO, but have an aluminium content near the substrate composition. Cyclic oxidation experiments were performed with Ni-Al, Ni-Pt-Al, and Ni-Pt-Al-Ir alloys in dry air and air-12%H2O. Thermal cycles of 1 hr at 1200OC and 10 minutes at 80OC were carried out in flowing gases at a total pressure of 1 atm. Experiments in N2- 12%H2O were performed only on Ni-Al binary alloys. Binary Ni-Al cast alloys were tested for fundamental study purposes, while Ni-Pt-Al and Ni-Pt-Al-Ir cast alloys were intended to be models for aluminide coatings, with attention focused on γ+γ' -Ni-(20 to 23)Al. Comparisons were made with β-Ni-50Al, as it forms an external alumina scale and was found to have the smallest weight loss rate during testing of binary alloys. Assessments of Pt and Pt-Ir additions, with and without hafnium, to the γ+γ' binary alloy were made. Compared to binary alloys, platinum was found to reduce the total weight loss caused by scale spallation. Experiments in air-12%H2O led to more rapid weight loss than in dry air. This was due to enhanced spallation. However, the degradation rate was slower than in platinum-free alloys exposed to the same atmosphere. Partial replacement of platinum with iridium was found to improve alloy scale adherence during exposure in both dry and wet air. Addition of 1wt% hafnium was found to reduce oxide thickness and increase the oxide adherence simultaneously. The hafnium addition was essential in order to reduce spallation rate in wet air. Water vapour in the presence of oxygen generally increased the spallation rate. It weakened the oxide metal interface, causing subsequent spallation to be increased, but only if the gas had access to the alloy-scale interface. Water vapour did not affect the spallation rate of the strongly adherent oxide grown on Ni-22Al-30Pt+1wt%Hf and Ni- 20Al-15Pt-10Ir+1wt%Hf.

This thesis outlines the results of an occupational hygiene monitoring program implemented at Minara Resources' Murrin Murrin mine site. The research was conducted as part of a collaborative agreement between Edith Cowan University and Minara Resources, the title of which was

The internal oxidation behaviour of Ni-base and Fe-base alloys containing approximately 5 at% Al and both with and without low concentration Cr additions in flowing low-oxygen atmospheres at 1273 K was studied. There were two groups of Febase alloys; ferritic alloys that were Fe-Al-Cr and others that also contained approximately 9.3 at% Ni in order to make them austenitic. Ni?base alloys were oxidised in oxygen partial pressures of either 4.6 ?? 10-11 atm or 9.8 ?? 10-13 atm and Febase alloys were oxidised in an oxygen partial pressure of 1.2 ?? 10-16 atm The aim of this investigation was to examine the effect of internal oxidation on Fe- and Ni-base alloys containing Al or Al with Cr. The morphology of the precipitates formed and rates of reaction were of interest. Oxidation of the ferritic Fe-base alloys produced internal oxidation only at lower solute concentrations. In these alloys steady state diffusion-controlled precipitation was prevented from occurring due to the formation of an oxide barrier at the reaction front, and cracking off of the internal oxidation zone. In all of the austenitic alloys (Ni-base and y-Fe-base) internal oxidation was observed after all exposures. In y-Fe-base alloys and in Ni-base alloys oxidised at the higher oxygen partial pressure (4.6 ?? 10-11 atm) precipitation zones were found to widen according to parabolic kinetics, indicating diffusion control. In Ni-base alloys oxidised at 9.8 ?? 10-13 atm, precipitation zones were observed to widen according to parabolic kinetics up to 40.9 hours. However, the rate slowed for longer reaction times due to coalescence of precipitates at the reaction front. The rate of internal oxidation decreased with increasing Cr, and thus total solute, concentration. The parabolic rate constants measured for internal oxidation were higher than predicted by Wagner's theory of internal oxidation, which is consistent with observations in previous studies. Kinetics were accelerated by the presence of elongated precipitates, aligned approximately normal to the alloy surface. Chromium alloy additions led to precipitate coarsening, and at lower oxygen partial pressures, to loss of elongated morphology. The precipitates formed were found to be a mixture of M2O3 and AM2O4, where M represents either Al or Cr, and A represents either Fe or Ni. Both oxide forms were detected at all depths within the internal oxidation zone. However, Cr-containing oxides were limited to the part of the internal oxidation zone closer to the alloy surface, while Al-containing oxides were present at all depths. This is consistent with thermodynamic predictions.

The miniaturization of Microtechnology-based Energy, Chemical and Biological Systems (MECS) is made possible by the use of high aspect ratio microchannel arrays to increase the surface-area-to-volume ratio of the flow conduits within the devices, resulting in an improvement in the heat and mass transfer performance of the devices. However, advantages of the MECS concept cannot be applied to high-temperature applications (above 650��C) due to lack of high-temperature MECS devices; therefore, the development of high-temperature MECS devices is necessary to overcome this bottleneck. This dissertation involves the development of high-temperature MECS devices from a high-temperature material, nickel aluminide (NiAl). NiAl foil was synthesized from elemental nickel (Ni) and aluminum (Al) foils through a two step process--tack bonding and reactive diffusion. The elemental foils were tack bonded at 500��C, 3.9 MPa for 15 minutes. The reactive diffusion process was then performed through a heat treatment at 1000��C for a period of time corresponding to the thickness of the composite foil. The synthesized NiAl foil showed an atomic ratio of Al to Ni up to 0.96. The foil also showed a decent flatness and surface roughness. This dissertation proposes a reactive diffusion bonding as a joining technique of nickel aluminides. An investigation of bonding parameter effects on the warpage of nickel aluminide fins in the reactive diffusion bonding process was performed. Results showed that bonding time and temperature had significant effects on warpage of the fin. The fin warpage increased with the increase of bonding time and bonding temperature. Results also suggested that the bonding pressure had an effect on the fin warpage. However, chemical compositions of the fin were not significant to the warpage. This research also proposes a new fabrication procedure for producing NiAl MECS devices. NiAl foils were used as the starting material, and the reactive diffusion bonding technique was employed as the joining technique. The research outcome indicated the viability of the proposed method in fabricating NiAl MECS devices. This method achieved leak-tight devices with a reasonable fin flatness. / Graduation date: 2003

For the induction heating process of bi-metallic tubes, the inner tube of alloy-layer is much easier to cause a lot of defects of cavities due to the fact that heating power, maximum temperature value and the time frame of temperature retention were chosen improperly. This research focuses on the effect of maximum temperature value and the time frame of temperature retention on the micro-structure and defects of cavities of the Nickel-based alloy-layer. The experiments of this study are divided into two parts. In the domain of the experiment in simulation fashion, Nickel-based alloy powders were put into the specimens of AISI 4140 steel. Radio Frequency (RF) oven were used to smelt Nickel-based alloy powders in the vacuum conditions over the maximum temperature range of 920~1180¢Jrespectively. After that, the time frame of temperature retention was conducted from 0 to 10 minutes. Then, the furnace-cooling went down to 700¢J then air-cooling down to the room temperature. Nickel-based alloy-layer, microstructure, component analysis, defects of cavities of the interface between Nickel-based alloy-layer and steels, and diffusion of interfaces were analyzed using optical microscopes (OM) and scanning electron microscopes (SEM). From the experiments, it was found that Nickel-based alloy-layer consisted of £^-Ni¡BCrB¡BCr7C3 over the maximum temperature range of 920~1050¢Jwhether temperature retention is performed or not. According to the findings of metallographic observation, the increase of coarsening and the reduction of the capacity of CrB and Cr7C3 become more obvious as maximum temperature value and the time frame of temperature retention become large. In addition, the whitening layer (diffusion zone) formed between the interface of alloy-layer and steels become much wider as maximum temperature value and the time frame of temperature retention become large. Secondly, the field experiment method was also applied in this paper. The tube rich in Nickel-based alloy powders was heating to analyze induction coil in various conditions: heating power (200~285KW), maximum temperature value (1020~1040¢J), the time frame of temperature retention (10, 30, 50sec), and the rotating speed (1000~1300rpm). The results of the experiments indicated that the surface of the alloy-layer cause defects of vermicular cavities since the volume of liquid cannot fill out the crack of cavities completely due to lower temperature when there is insufficient time; too long periods of the time frame of temperature retention lead to the tough and huge dendrites to obstacle the flowing of liquid and the solidification of shrinkage cavity. According to the observation of the microstructure, the larger the maximum temperature value and the time frame of temperature retention were, the more the dendrites formed. The formation of dendrites causes not only the uneven distribution of hardening phase of CrB and Cr7C3 of the alloy-layer but also the reduction of hardness of the alloy-layer. The dendrites are typically formed from the interface to the surface of the alloy-layer. Besides that, the alloy-layer mainly consists of £^-Ni, Ni3B, Ni3Si, CrB, and Cr7C3 via X-ray Diffraction (XRD). Among them, the main hardening phases are CrB and Cr7C3 which is the main reason that the alloy-layer has high-level hardness. As maximum temperature value and the time frame of temperature retention become large, the whitening layer (diffusion zone) was formed between the interface of alloy-layer become much wider because the faster the elements of the based materials (tube) diffused and the wider the intermetallic compound formed among the interfaces. After heated for 800 seconds over the temperature range of 750~1030¢J, iron element was diffused all over the alloy-layer. The increase of coarsening and the reduction of the capacity near interface and interface become more obvious as maximum temperature value and the time frame of temperature retention become large.