Applicability of Monte-Carlo method for the textural and microstructural changes during annealing processes is studied. Models that are developed for explaining annealing processes are incorporated into Monte-Carlo procedures and the textural and microstructural changes are then followed. The simulated results are compared with the experimental observations to validate the proposed models, The three exemplary annealing processes selected for the present work are industrially important and diversified in their annealing characteristics, These are: (I) Cube {100}⟨001⟩ texture development during recrystallization of Al, (II) Abnormal grain growth of Goss {110}⟨001⟩ grains in Fe-Si steels, (III) The competition between (111) and (100)-fiber textures during annealing of nanocrystalline Ni and Ni-Fe alloy electrodeposits. The model for each annealing process is developed by analyzing the relevant metallurgical information obtained from the corresponding metals and alloys prior to annealing, / In Application-I, the texture and orientation-dependent stored energy measurements have been made on the cold rolled can-body aluminum alloy and the detailed discussion is presented, These results are analyzed for developing nucleation and growth models that would lead to the final cube texture formation during primary recrystallization of aluminum. The proposed recrystallization model for aluminum predicts the development of cube texture and equiaxed grain structure as observed in experiments. / For the abnormal grain growth in Fe-Si steel (Application-II), the role of high energy grain boundaries has been studied in detail using separate computer experiments to understand the importance of fraction of high mobility grain boundaries. From these experiments, it has been proved that the assumption of high mobility to CSL boundaries for the abnormal growth of Goss grains is not valid. / Finally, the Monte-Carlo procedure is employed for testing the proposed model for the texture competition between (111) and (100)-fibers in nanocrystalline Ni, Ni-20% Fe and Ni-45% Fe electrodeposits (Application-III). Based on the texture analysis, the proposed model assumes high mobility to the grains boundaries, which are in high non-equilibrium states. The results of the Monte-Carlo simulation using the proposed model are compared with experiments, The simulated results show that (111)-fiber grows faster than (100)-fiber as annealing progresses. (Abstract shortened by UMI.)

A novel process to efficiently produce anhydrous, oxide free MgCl 2 feed to a magnesium electrolysis cell is presented and examined in this thesis. The process involves reducing MgCl2 activity within a fused salt mixture via complexation and reacting any contaminating oxides that are mostly MgO with HCl(g). This process would not be possible nor economical if the MgCl2 activity was not reduced via complexation. This system is modeled here by treating the complexation as decreasing the MgCl2 activity coefficient in a fused salt mixture. / The chlorination was modeled thermodynamically using recently published thermodynamic data presented by Thompson et al. The model was experimentally verified. A kinetic model was also developed for the heterogeneous reaction between injected HCl gas and the MgO in fused salt. It was found that the rate of MgO elimination was proportional to C2/3MgO in the fused salt during the course of a kinetic batch test. The implication is that the rate of transport per unit area of MgO, of HCl to the MgO surface is constant for any particular condition which is only possible if the mass transport of HCl to the MgO particle surface is rate limiting. / The kinetics of MgO conversion were measured as a function of superficial gas velocity and mixing power per unit volume. The following relation empirically describes the conversion rate per unit area of MgO particle surface area wt%/min/m 2 for a given operating condition. km=0.001895Pg Vm0.8 3Vst 0.92 / Analysis of the kinetic information, confirmed the hypothesis for the mechanism of MgO elimination. / Measurements of the solubility of HCl(g) in fused salts were also taken. The findings show that the solubility of HCl varied between 270 ppmw to 2760 ppmw when the MgCl2 concentration was increased between 20 wt% to 70 wt% at 600°--650°C and a NaCl to CaCl2 weight ratio of 2.5--3.1. A mechanism for dissolution is presented.

The study emphasizes the effects of multi-pass narrow gap (NG) Submerged-Arc welding (SAW) on the Heat Affected Zone (HAZ). The differences between the HAZ of single-pass welds and multi-pass welds are radical and are caused by the subsequent thermal cycles which only exist in multi-pass welding. / A series of experiments were carried out to establish the relationship between the welding thermal cycles and the mechanical and microstructural properties of a HAZ. Both real and Gleeble simulated HAZ's were investigated. / Theoretical and experimental analyses indicate that the HAZ's in multi-pass welds can be improved significantly by the welding process itself. However, multi-pass welding does not always improve its HAZ. To realize the improvement, some special criteria must be met. The most important parameters are heat input, welding speed, deposit thickness and inter-pass temperature. This study establishes the relations between these parameters and the effects of HAZ refinement. There are some domains of the parameters in which HAZ refinement can be realized. The research reveals that in multi-pass NG welding, a set of welding parameters can always be found to fulfill the conditions for HAZ improvement. / Real welding processes, with welding parameters optimized according to the analyses, were performed and a totally refined HAZ was achieved under laboratory conditions. It is suggested that the method can be applied to in situ welding situations. / High heat input does not necessarily lead to inferior microstructural and mechanical properties in multi-pass NG welding. As long as the conditions for HAZ refinement are satisfied, an improved HAZ will be obtained no matter how high the heat input is. This also leads to the conclusion that the HAZ in multi-pass NG welding is less sensitive to heat input than that in single pass welding. / The tempering parameter, which has been used to evaluate the tempering effects at constant temperature, is successfully introduced into welding (non-isothermal) conditions. The effects of precipitates in 2.25Cr-1Mo steel are theoretically investigated.

The evolution of advanced ceramic materials over the past two decades has not been matched by improvements in ceramic joining science and technology, particularly for high temperature applications. Of the techniques being evaluated for joining ceramics, brazing has been found to be the simplest and most promising method of fabricating both ceramic/ceramic and ceramic/metal joints. A key factor in ceramic brazing is wetting of the ceramic by the filler metal. / This study deals with the application of brazing for the fabrication of $ rm Si sb3N sb4/Si sb3N sb4$ and $ rm Si sb3N sb4/Mo$ joints using Ni-Cr-Si brazing alloys based on AWS BNi-5 (Ni-18Cr-19Si atom%). Thermodynamic calculations were performed to predict wetting at $ rm Si sb3N sb4$/Ni-Cr-Si alloys interfaces. By using some simplifying assumptions and suitable scaling of the reaction, the model predicted that Ni-Cr-Si alloys with Ni/Cr = 3.5 and X$ sb{ rm Si}$ $<$ 0.25 would react chemically with and wet $ rm Si sb3N sb4$. Good agreement was found between the theoretical calculations and experimental results. / Brazing experiments were carried out to study the joinability of $ rm Si sb3N sb4$ with various Ni-Cr-Si filler metals which had already shown good wetting characteristics on $ rm Si sb3N sb4$. The $ rm Si sb3N sb4/Si sb3N sb4$ joints formed with a 10 atom% Si brazing alloy exhibited the highest strength ($ approx$120 MPa) which was mainly due to the presence of a CrN reaction layer at the ceramic/filler metal interface. The high temperature four-point bend strengths of $ rm Si sb3N sb4/Si sb3N sb4$ joints were markedly higher than the room temperature values. A high strength of about 220 MPa was achieved when the joints were tested at 900$ sp circ$C. / From the results of the $ rm Si sb3N sb4/Mo$ joining experiments it was found that the joint quality and microstructure were strongly influenced by the composition of the filler metal and such brazing variables as time and temperature. Of all the $ rm Si sb3N sb4$/Mo joints, those made with the S10 brazing alloy at 1300$ sp circ$C for 1 min. exhibited the highest strength of 55 MPa. / Finally, in all the cases, the shear strength of all the joints was found to be lower than their four-point bend values.

No description available.

The present work attempts to determine the feasibility of the accelerometer as an end-point control sensor for the basic oxygen steelmaking process. In this study, two series of laboratory scale BOF simulations were performed. In the first series, the accelerometer was sampled at low frequency to obtain an amplitude-time relation that can be related to the rate of decarburization during the oxygen blow. In contrast, the accelerometer was sampled at high frequency in the second series in order to discern the presence of specific vibrational frequencies that can be related to the process. As a final aspect of the research work, several high frequency simulations were terminated prematurely in an attempt to elucidate the carbon content of the bath at the point in time when the accelerometer can clearly detect the final change in the rate of decarburization.

An investigation of copper matte vacuum purification was undertaken. A mathematical model using monatomic, diatomic sulphide and diatomic oxide vapours of the impurities was developed to explain the vacuum refining process. The model was used to predict the overall refining rates for variables such as temperature, matte grade, oxygen activity and chamber pressure of the melt. / A series of experiments was undertaken to characterize the dust produced during vacuum refining of copper matte. An attempt to selectively condense the vapours produced during the vacuum refining experiments was carried out. / The "Lift-Spray" vacuum refining process was used to refine 15 to 40 kg batches of molten copper matte containing 35 to 78% copper. The removal rates of lead, bismuth, arsenic, antimony, selenium, nickel and silver were measured under different levels of matte grade, chamber pressure, lifting gas flow rate and dissolved oxygen content in the melt. The ranges of the variables under study were from 10 to 600 pascals chamber pressure, 0 to 40 normal milliliter per second of lifting gas flow rate and 10$ sp{-16}$ to 10$ sp{-7}$ atmosphere of oxygen activity. / In conclusion, LSV refining of copper matte was shown to be a promising process. Furthermore, scale-up to industrial size is now possible. The scale-up dimensions compare well to the dimensions of the RH degassing unit presently used in the steel industry. (Abstract shortened by UMI.)

With the aim of simulating the hot rolling process, single and double hit compression tests were performed in the temperature range 800 to 1200$ sp circ$C at strain rates of 0.2 to 50 s$ sp{-1}$ on selected low carbon steels containing niobium, boron and copper. The stress/strain curves determined at high strain rates were corrected for adiabatic heating and constitutive equations were formulated. When dynamic recovery is the only softening mechanism, these involve a rate equation, consisting of a hyperbolic sine law, and an evolution equation with one internal variable. When dynamic recrystallization takes place, the incorporation of the dynamically recrystallized fraction in the above evolution equation makes it possible to predict the flow stress after the peak. / The kinetics of static recrystallization were characterized in terms of the mean flow stresses, which lead to more accurate results than alternative methods. Appropriate expressions were formulated for the recrystallization kinetics and the mean austenite grain size as a function of predeformation, temperature and particularly strain rate. / Particular attention was paid to prediction of the temperature distribution through the thickness of the rolled plate or strip. The effects taken into account are radiation and convection from the surface when the material is between stands, and conduction to the rolls and the temperature increase due to mechanical work when the material is in the roll gap. An explicit finite difference method was used to calculate the temperature distribution through the thickness of the workpiece during processing. / On the basis of the temperature model and the constitutive and recrystallization kinetics equations, a computer model for the prediction of multi-stage rolling force and microstructural evolution was developed. The predictions of these models are in good agreement with measurements on both experimental and commercial steels. Also, by appropriate control of the thermomechanical parameters, high strength steels with transition temperatures below $-$100$ sp circ$C were developed. These results constitute a step towards the on-line control of plate and hot strip mills, and the development of new tough high strength steels.

Solid residues are generated at various stages of metal production. Some of these residues still contain significant quantities of metals. In determining possible process routes for residues a detailed knowledge of the mineralogy (i.e. the minerals or phases present) is required. This thesis examines the mineralogical characteristics of four residues: copper smelter dust, jarosite residue and hot-acid-leach residue all from the metallurgical plant of Kidd Creek Mines Ltd., and low-acid-leach residue from the Canadian Electrolytic Zinc plant. / The methodology of characterization included the fractionation of the residues based on particle size, magnetic susceptibility and leachability in sulphuric acid. The fractions were analyzed by X-ray diffractometry and electron beam techniques. / A major phase in all the residues was zinc ferrite. The characterization of this phase showed that it does not have the stoichiometric composition of ZnFe$ sb2$O$ sb4$ but exhibits a variable composition of the type Zn$ sb{x}$Fe$ sb{3-x}$O$ sb4$. This variable composition corresponds to a measured variation in magnitude susceptibility of the ferrites. / Some treatment routes for these residues are examined; special emphasis was placed on the potential application of magnetic separation. The hot-acid-leach residue appeared the most amenable to magnetic separation.

In order to design the metal delivery system for the single belt caster in the MMPC (McGill Metals Processing Centre) foundry, water modeling and mathematical modeling were carried out for a newly devised three-chamber type tundish. Water flow in the acrylic tundish was visualized using dye injection. Flow velocities were also measured using a Dual Nd-YAG PIV (Particle Image Velocimetry) system. A commercial FEM code, FEMLAB 2.3 was adopted to predict the velocity field and temperature profile within the tundish, especially in the output chamber. Calculated results were validated with the PIV measurements. A full-scale water model was built for the single belt caster to simulate the casting operation and to validate the optimized delivery system. Temperature profiles for the tundish wall were also predicted to choose a suitable method of preheating and to determine refractory wall specifications. / A three-chamber type tundish comprising an entry chamber, a head control chamber and an output chamber was designed to provide clean metal and strips of uniform thickness across the width of the belt. An output chamber proved to be essential for removing the bubbles and for obtaining a uniform film of water on the substrate by preventing strong hydraulic jump. The output chamber had to be completely closed for rapid bubble removal. For rapid filling of the output chamber at start up, the starting stopper proved to be essential. The 3-hole type nozzle, proved to be more effective for removing the bubbles, was found to have problems in terms of strongly impinging jet flow and non-uniform lateral velocities. / Using mathematical modeling and full scale water modeling, including PIV measurements, the "FD" type nozzle, which had a multi channel flow modifier in the output chamber and a slot type inlet nozzle, was found to be the best in terms of rapid bubble removal and uniform distribution of flow. This was achieved by a dramatic reduction in the strength of the vertically impinging flow towards the belt. However, this "FD" type nozzle generated a dead zone near the triple point within the output chamber. To remove the dead zone, a gently sloped shape insulator was inserted between the tundish back wall and the belt.