The effects of the three factors (modification, grain refinement, and hydrogen level) on the amount of porosity, impact strength, and performance of the reduced pressure test in A356 alloy have been studied. It was found that grain refinement, acting singly and in combination with modification, reduces the porosity by inducing mass feeding. However, this beneficial effect may not be found at all cooling rates and casting sizes. There is less total shrinkage in Sr-alloyed samples than in those which are non Sr-alloyed. The reason for this is supposed to be a difference in the liquid density which may be higher in Sr-alloyed samples. Modification has the strongest effect on improving the impact strength of A356 alloy. Hydrogen reduces it slightly. On the other hand, grain refinement, acting singly or in combination with modification, was not found to improve the impact strength of the alloy. To obtain optimum impact strength, it is recommended that a combination of modification and degassing to about 0.1 ml.H$ sb2$/100 g. Al. be used. An excellent linear relatiosnhip between density and hydrogen level exists for all combinations of melt treatment processes when the redued pressure test is used. Three methods of predicting the true hydrogen level are proposed and calculated hydrogen levels agree reasonably well with measured melt hydrogen within the error range of $ pm$0.05-0.1 ml./100 g. Al.

The development of advanced metal products requires "clean" liquid metals as their basic materials. There are more and more applications for which the cleanliness of the liquid metals has to be qualified that the number and size of inclusions must be controlled below some acceptable limits. Such demands for quality have resulted in the development of measuring systems that can count the number and size distribution of inclusions. One such device, the so-called LiMCA (Liquid Metal Cleanliness Analyzer), which was developed at McGill University, measures inclusions in liquid metals and has been successfully used in the aluminum industry for years. / Digital Signal Processing (DSP) technology has been successfully applied to upgrade the LiMCA system. With this technology, the DSP-based LiMCA system is able to describe each LiMCA transient by a group of seven parameters, and with the help of them, classify it into a certain category. Moreover, it simultaneously counts the classified peaks based on their height and their time of occurrence. (Abstract shortened by UMI.)

The zirconium/hafnium separation, as currently practiced, is mostly carried out by solvent extraction in which the aqueous chloride solution of metals is contacted with an immiscible organic phase containing a reagent that removes hafnium leaving zirconium in the aqueous solution. Hafnium is extracted as its thiocyanate complex using methyl isobutyl ketone (MIBK). There are environmental consequences of this system that were acceptable when the process was developed but should become a serious problem as legislation becomes more stringent. These problems are primarily the high aqueous solubility of MIBK and the potential for toxic gas generation. This work has tested four organophosphorous reagents to separate zirconium from hafnium without the need of thiocyanate, avoiding toxic gas formation. The extractants and diluent have very low aqueous solubility, removing effluents control problems. We see these features as representing a "zero waste" process. Additional advantages over MIBK process are lower vapor pressure and higher flash point (lower fire risk). This work presents the lab-scale experimental results using mainly two reagents designated by Cytec Canada Ltd as Cyanex 923 and Cyanex 925. The key feature of this work is replacement of MIBK and thiocyanate with one of a family of organophosphorous extractants that were unavailable in the 1950's at the start of the MIBK process. This work shows they can be efficiently applied to hafnium/zirconium separation in aqueous chloride solution, with minimum adjustments of the present industrial practice.

Sludge combustion experiments were performed using a computer-controlled thermogravimeteric system. Microscopy and spectometry techniques were used to determine ash morphologies and structures, metals distribution inside ash particles and leachability of toxic metals from ash. Parameters examined included temperature, residence time, heating rate and cooling rate. / The combustion process consisted of four stages: initial burning, transition, sintering and melting. It was found that temperature has the greatest effect on ash morphologies and metals distribution in the ash particle. It was observed that light metals predominated in the surface layers of the ash particle while heavy metals were mostly partitioned in the core area. As the temperature increased, leaching of heavy metals from ash decreased significantly. At temperatures above 1200$ sp circ$C, no toxic metals were leached out. Such ash particles could be safely disposed of and reused.

An inclusion sensor system for liquid metals first developed at McGill and dubbed with the acronym, LIMCA, is now in daily use for monitoring metal quality in ALCAN's casting centers. This method can simultaneously provide the number density, and size distribution, of inclusion particles in molten metals. / Attempts have been made to extend the LIMCA technique to analyses of steel cleanliness. In order to commercialise the LIMCA system, a batch type probe, similar to an oxygen sensor, was developed and tested in low carbon steel melts. / For industrial applications, a series of experiments was carried out in a 60 ton tundish at DOFASCO. The data derived from these LIMCA measurements were compared to those obtained by DOFASCO personnel using the 'slime' technique for inclusion detection.

Modification of the eutectic silicon in Al-Si foundry alloys by adding strontium is accompanied by an increase of porosity in the casting. This effect on porosity is due to an increase in both the pore size and the pore number density. In an attempt to understand the nature of this problem, the effect of strontium on the probable causes for porosity occurrence due to modification has been investigated. / Experimental findings indicate that the addition of strontium to Al-Si alloys increases the volumetric shrinkage due to an increase in solid density, and at the same time reduces the surface tension and increases the viscosity of the liquid. Metallographic observations show that Sr addition slightly decreases the dendrite arm spacing and changes the solid-liquid interface to a more regular shape. Moreover, Sr-modification decreases the eutectic temperature, and therefore, increases the length of the mushy zone while the total solidification time remains constant. / In addition, Sr addition increases the melt inclusion content, but these inclusions do not have a significant effect on pore nucleation. Hydrogen measurement in the liquid shows that Sr-modification has no effect on the rate of melt hydrogen pick-up and does not introduce hydrogen into the melt. Strontium also reduces the hydrogen solubility in the liquid state but has virtually no effect on the solid state solubility. / A solidification model for pore formation has been developed to study the significance of the changes in these parameters on porosity formation. Based on the experimental results and the theoretical analysis, it is concluded that the decrease in the hydrogen solubility in the liquid, the eutectic temperature (or the length of the mushy zone) and the surface tension are the reasons for the observed increase in porosity in modified alloys. Among these parameters, the decrease in the hydrogen solubility in the liquid plays the main role in causing enhanced porosity formation.

This thesis presents fundamental research about the combustion gas products and solid phase residue of switch grass combustion. To identify the compounds released during the combustion phase, tests were conducted using a Thermogravimetric Analyzer (TGA) coupled to a Fourier Transform Infrared Spectrometer. These test revealed that aromatic compounds as well as carbon dioxide and water were released. / High Pressure Liquid Chromatography (HPLC) and GCMS/GCFID were also used to identify and semi-quantify polycyclic aromatic hydrocarbons (PAH) and benzene derivatives. From these analyses it was concluded that thermal synthesis was not occurring within an oxidative environment and as such no PAHs were found. / Finally an infrared microscope and a scanning electron microscope were used to study functional group, morphology and metal content change resulting from the combustion process. / This research provided information about the combustion mechanism of switch grass and laid the foundation for pilot-scale testing.

ThermoMechanical Processing (TMP) is a tool whereby a controlled microstructure and mechanical properties are achieved by a combination of controlled deformation and heat treatment steps. However, because there exists a trade off between strength and ductility, steels destined for both high formability and high strength applications must further undergo a sequence of energy intensive heat treatment steps. Alternatively, TRIP (TRansformation Induced Plasticity) steels have been acknowledged to possess excellent combinations of both strength and ductility. The timely strain or stress induced transformation of Retained Austenite (RA) to martensite locally strengthens these steels at the point of plastic instability, causing failure by necking to be postponed and shifted elsewhere along the steel. This phenomenon repeated over and over again allows increased levels of deformation, prior to fracture. / In the current TRIP grades, Si is a key elemental addition. However, in levels exceeding 1.0 wt.%, it is unpopular as it is responsible for a tenacious oxide layer. In this work, it is suggested that Mo may potentially replace Si in part. / Multi pass rolling simulations were also performed using torsion. (Abstract shortened by UMI.)

Sludges formed by lime treatment of acidic mine effluents are a widespread environmental hazard. One treatment option is to recover the toxic and potentially valuable contained metals. A method has been reported to selectively recover the metals by leaching with a complexing agent, diethylenetriamine (DETA). In this thesis a novel method has been developed to recover metals from the metal---DETA complexes by direct electrowinning. Copper was studied initially as a test system due to the relative ease with which it is recovered in conventional sulphate electrowinning. The main industrial interest, and hence the main focus of the work, is in the nickel---DETA system. For both metals, initially batch tests were run to determine acceptable electrowinning conditions. These were followed by recycle tests to simulate a potential process flowsheet. In the nickel-DETA system the effects of pH, nickel concentration, temperature, and DETA to nickel ratio on current efficiency were determined. / Recycle tests for copper showed that a steady DETA concentration was achieved after ca. six hours. In the case of nickel, the system seemed to continually deteriorate. A pH range of 4.6 to 4.8 maximized the current efficiency, due to a competition between hydrogen formation at low pH and increased complex stability at high pH. Both increasing Ni concentration and temperature increased the current efficiency, while increasing the DETA to nickel ratio lowered it.

Industrial mill logs from 7 different hot strip mills were analyzed in order to calculate the mean flow stresses developed in each stand. The schedules were typical of the processing of Nb microalloyed, multiply-alloyed and plain C-Mn steels. The calculations, based on the Sims analysis, take into account work roll flattening, redundant strain and the forward slip ratio. The measured stresses are then compared with the predictions of a model based on an improved Misaka mean flow stress equation, in which solute effects, strain accumulation, as well as the kinetics of static and metadynamic recrystallization are fully accounted for. Good agreement between the measured and predicted mean flow stresses is obtained over the whole range of rolling temperatures. The evolution of grain size and the fractional softening are also predicted by the model during all stages of strip rolling. Special attention was paid to the Nb steels, in which the occurrence of Nb(C,N) precipitation strongly influences the rolling behaviour, preventing softening between passes. The present study leads to the conclusion that Mn addition retards the strain-induced precipitation of Nb. By contrast, Si addition has an accelerating effect. The model calculates the critical strain for the onset of dynamic recrystallization in Nb steels. It shows that the critical strain/peak strain ratio decreases with increasing Nb content, and that Mn and Si have marginal but opposite effects. It is demonstrated that dynamic recrystallization followed by metadynamic recrystallization occurs under most conditions of hot strip rolling, during the initial passes due to the high strains, low strain rates and high temperatures, or in the final passes as a consequence of strain accumulation.