For TRIP steels to be included as a future structural steel in automobile industries, the drawbacks associated with high silicon (more than 1%) must be solved. To this end, TRIP steels, with aluminum as a substitute for the silicon, have been under investigation by many groups. / In this work, the approach is to investigate the effect of hot deformation on the microstructure and the mechanical properties of the aluminum containing TRIP steels. The problem with these steels is that the strength is reduced compared to classical Si TRIP steels. In this work, a number of mechanisms could contribute to the strengthening, including refining the austenite grain and work hardening of ferrite. These may also affect the retained austenite characteristics. / Two different C-Mn-Al TRIP aided steels with aluminum contents of 1.43 wt % and 2.0 wt % were investigated and compared with a typical TRIP steel containing 1.5 wt % Si. To determine the critical hot working temperatures, the FactSage software was used to predict the phase diagram and the critical temperatures were confirmed by heat treatment and metallography of the quenched specimens. Using these data, hot deformation experiments were performed to investigate the influence of the deformation temperature and the strain within the intercritical region by using a Gleeble simulator. (Abstract shortened by UMI.)

Steel media wear has been well studied and quantified; one method of quantification is the Comminution Dynamics Lab's Total Media Wear model. It combines simulations, abrasion and corrosion experimental trials to determine wear for the components of milling and grinding ores and minerals for the mining industry. Breakage is an important measure of process efficiency, the greater the number of breakage events per unit energy consumed, the greater the throughput and production. The classic breakage parameter, the Bond Work Index generates an energy term used by mill operators to determine this performance criterion. It has been suggested that the abrasion test, used in the Total Media Wear Model, would be a suitable alternative to the labour and time-consuming Bond Locked-cycle Test. Extensive tests were performed in order to ascertain the possibility of obtaining these two desired results from a single two-minute test. Different steel media samples were tested at different energy levels, and finally by testing under wet and dry conditions. Dry and wet testing did not generate the same wear results. Wear and breakage rates were higher under wet conditions. In general, the size distribution of the abrasive feed evolved into a product with a finer size distribution. Statistical analysis of the data obtained suggests that there is indeed a linear relationship between the energy input into the system and the resultant Work Index value. These results support the suggestion that this test will be able to recreate the Bond Work Indices for minerals; however, more work is required in order to build a working database and determine appropriate correlation factors. / L'usure des composants ferriques dans les procédés minéralurgiques et un sujet bien étudié. Le laboratoire « Comminution Dynamics » a McGill à crée un modèle nommé « Total Media Wear Model » pour prédire le temps de l'avance nécessaire avant lequel il faudra remplacer les blindages et boulettes. Cette modèle comprend des simulations informatiques et des tests de laboratoire. Une autre mesure utilisée par les contremaitres et operateurs c'est le « Bond Work Index ». L'index donne une valeur approximative pour prédire la consommation d'énergie des moulins. Un test du style « Bond » exige beaucoup d'effort, et temps. Récemment, il a été suggérer qu'on pouvait obtenir des valeurs pour le « Bond Work Index » en utilisant un procédé modifié pour un des tests du « Total Media Wear Model ». Différentes nuances d'acier on été testé avec des niveaux d'énergie variées et sous des conditions sec et humide. Les résultats on démontré que les tests sec/humides n'était pas nécessairement équivalent, de plus, un changement dans la distribution granulométrique s'est produit entre la charge et le produit. Et finalement, l'analyse des données suggère qu'il y a une relation entre la valeur calculée de « Work Index » et l'énergie introduit dans la système. Ces résultats confirment les croyances qu'on pourra déterminer la valeur de « Bond Work Index » en même temps que les données du « Total Media Wear Model ». Cependant, il faudra des tests supplémentaires pour plusieurs types de minéraux. Cela pourra crée une base de données avec lequel des facteurs de corrélations pourront être déterminer.

Gravity-Recoverable-Gold (GRG) is defined as gold present in a particle in sufficient quantities as to be selectively recoverable from gangue via gravity methods. The McGill standard GRG test is an ore characterization test using three stages of sequential liberation and recovery with a Knelson KC-MD3 centrifuge to determine the size distribution of GRG. This thesis describes the development and testing of two simplified versions of the GRG test, using two and one stages of recovery respectively. Both tests use a feed mass of 20 kg, as opposed to the 40 to 100 kg normally used for the standard test. Eighteen differing ore samples were processed with the simplified GRG tests. For non-abrasive ores the one-stage simplified test returns a similar GRG content and size distribution, making the two-stage test superfluous. For abrasive ores, the one-stage test returns a GRG content that can be as much as 33% relative lower than that of the standard test, with a much finer size distribution. The two-stage test exhibited similar poor performance, though to a slightly lesser degree due to and additional stage of recovery attempted prior to grinding the abrasive material. The GRG lost typically reports to size fractions coarser than 25 &mgr;m, strongly suggesting smearing onto gangue particles. Because of the lower feed mass used, both simple tests are susceptible to the nugget effect; feed representativity also becomes challenging for ore samples of a head grade of 1 g/t or less.

The INCO finishing procedure represents the near final stages of copper production at the Copper Cliff Smelter in Sudbury, Ontario, whereby semi-blister copper, at 4--6 wt % Ni and 2--3 wt % S, is processed into blister copper, at 100 ppm S and 0.4 wt % Ni in a modified Pierce-Smith converter combining top-blown oxygen injection and bottom-blown nitrogen stirring of the melt to accelerate semi-blister desulfurization. The procedure is performed in two stages of equal duration: in the first, melt saturation with oxygen and sulfur elimination from 2--3 wt % S to 300 ppm is achieved by 45 minutes of oxygen top-blowing and nitrogen bottom stirring; in the second stage, oxygen injection is terminated and sulfur removal from 300 ppm to 30--100 ppm. proceeds by the ppm to 30--100 ppm proceeds by the reaction of dissolved S and O under a further 45 minutes of nitrogen stirring. / Cu-S and Cu-Ni-S alloys were also exposed to the open atmosphere to examine desulfication of stagnant melts under air. (Abstract shortened by UMI.)

This thesis presents the results of an investigation on the impact of continuous circuit and solution parameters on coprecipitation of arsenic with ferric iron from acidic sulphate solution. The techniques employed were selected, or developed, to emulate industrial practice. The concept behind the work was to better understand the link between the process of precipitation and the stability of arsenic in the resultant coprecipitates. This was performed by examining the role of circuit design and co-ions on both arsenic removal during coprecipitation and arsenic retention during ageing. The parameters/factors investigated included continuous versus batch operation, number of stages (pH profile), recycling and Ca2+, Ni2+ and Al3+ as co-ions. Arsenic removal was found to be greatly improved by continuous rather than batch coprecipitation. In addition, the presence of calcium (introduced as slaked lime) was found to be instrumental in the removal and retention of arsenic. Arsenic retention during ageing (up to 300 days) at various temperatures (3, 22, 40 and 70°C) was observed to reach an "equilibrium" that was strongly affected by the continuous circuit design, as well as the co-ions present during coprecipitation. Evidence is presented of the partitioning of arsenic within the coprecipitates in two principal phases, namely ferric arsenate (FeAsO4•xH2O) and arsenic adsorbed ferrihydrite. Continuous circuit design parameters, such as staging, that resulted in enhanced stability appear to yield coprecipitates with higher ferric arsenate content. Analysis of the kinetic and "equilibrium" arsenic retention data yielded activation energy (~ 60 kJ/mol) and enthalpy (~ -38.5 kJ/mol) values that suggest a reaction controlled exothermic dissolution mechanism. / Ce mémoire de maîtrise présente les résultats d'une étude portée sur la co-précipitation de l'arsenic et des ions ferriques en solution aqueuse sulfatée. L'utilisation d'un procédé continu et les paramètres de la solution ont été considérés comme cibles d'étude. Les techniques employées ont été sélectionnées ou développées afin de simuler les méthodes opératoires industrielles. L'idée directrice de ce travail était d'aboutir à une meilleure compréhension sur les liens entre les mécanismes de précipitation et la stabilité de l'arsenic dans les co-précipités formés. Aussi, le rôle du design du procédé ainsi que celui des co-ions sur l'extraction, respectivement la stabilisation de l'arsenic ont fait l'objet d'un examen approfondi à court terme soit au stade de co-precipitation, respectivement à long terme durant le vieillissement de la solution. Les paramètres/facteurs étudiés incluaient le caractère continu du procédé (en comparaison avec un procédé discontinu), le nombre d'étapes (le profile pH), le recyclage des produits solides et la nature (Ca2+, Ni2+ et Al3+) des co-ions introduits dans le système. Cette étude a montré que l'utilisation d'un procédé continu (en comparaison avec un procédé discontinu) améliorait considérablement l'extraction de l'arsenic à partir de solutions aqueuses sulfatées. Aussi, la présence de calcium (introduit sous forme de chaux hydratée) s'est avérée profitable à l'extraction de l'arsenic à court et à long terme. Il a été observé que la stabilisation de l'arsenic dans le cas des expériences de vieillissement (d'une durée de 300 jours) performées à différentes températures (3, 22, 40 et 70°C) atteignait un état d'équilibre fortement influencé par le design du procédé continu ainsi que par les co-ions présents lors de la co-précipitation. Il a été mis en évidence que lors de la phase de co-précipitation, l'arsenic était réparti sous forme de de

Strain and temperature gradients are developed through the cross-section during the hot rolling of steel rods. These gradients are of particular interest because of their potential effects on the homogeneity of the resulting microstructure during rolling as well as in the final product. Strain and temperature can strongly influence recrystallization and transformation behaviour. / A three-dimensional, temperature-dependent viscoplastic finite element analysis was used to predict the strain distribution developed for the hot rolling of steel square billets using the software package ABAQUS/EXPLICIT$ sp{ rm TM}.$ Constitutive parameters were determined from previous experimental data generated at McGill University and at the Metals Technology Laboratory (MTL), CANMET. / McGill-CANMET's Property Prediction Model was used to determine the microstructure during rolling and the final properties at room temperature. / Results from the mechanical and microstructural models were validated with experimental data from literature and from rolling tests performed at MTL-CANMET. / With these two models, several different hot rolling scenarios were generated to examine how the two models would predict their results by varying a single parameter.

The formation of iron-bearing intermetallics in the 413 type of aluminum alloys was investigated comprehensively. Both synthetic and commercial 413 alloys were studied with iron concentrations in the range of 0.4-1.2 wt. % and manganese up to 0.5 wt.%. The effects of cooling rate during solidification and of melt chemistry on the morphology of iron intermetallic phases were determined. Image analysis was used to quantify the intermetallic size, volume fraction, and number, as a function of both melt chemistry and cooling rate. The total volume fraction of intermetallic compounds in these alloys was related to cooling rate by an exponential equation. / The kinetics of both dissolution of intermetallics on melting, and of re-formation on cooling of the liquid were investigated by means of quenching experiments. Quantitative evaluation of intermetallic size and number revealed that the change in volume fraction of intermetallics in the liquid state is controlled by nucleation. / The effect of settling time and the rate of gravity segregation of intermetallic compounds in a stagnant liquid metal were investigated. It was found that, in the absence of convection, settling obeys Stokes' law with the terminal velocity reached at very short times and very close to the melt surface. / Strontium was used to modify or eliminate the iron-intermetallics. (Abstract shortened by UMI.)

A comprehensive characterization of silver and bismuth refining crusts produced during the pyrometallurgical refining of lead was undertaken. Parameters such as intermetallic crystal size and composition, and degree of metal entrainment were determined. Silver crust was found to be composed mostly of the $ epsilon$-phase (AgZn$ sb3$) with an average particle size of 50 $ mu$m. Liquid lead entrainment of 80 volume percent was measured. The intermetallic phase in bismuth crust was composed entirely of CaMg$ rm sb2Bi sb2$ crystals with an average diameter of 50 $ mu$m. Lead entrainment in bismuth crust was approximately 90 volume percent. The high degree of metal entrainment observed in both silver and bismuth crusts was not adequately explained through a capillary model of liquid metal entrainment in a static bed of solid particles. The models used to predict swelling in colloidal particle systems (such as clay soils) were found to better approximate the high degree of liquid entrainment. / Experiments were performed in which particle beds of $ gamma$-phase ($ rm Ag sb5Zn sb8$) intermetallic compound were infiltrated with liquid lead under controlled conditions and examined under the optical microscope. Image analysis revealed pronounced swelling of fine particle beds relative to coarse. The effect was most noticeable for average particle diameters less than 100 $ mu$m where the solids volume fraction decreased from 50 to 30 vol.%. Data showed samples LO exhibit a constant increase in inter-particle spacing of approximately 50 $ mu$m. The increase in spacing explained the degree of swelling at low particle diameters and was also used to develop an expression to predict height of capillary rise. / Based on an osmotic pressure analogy in colloidal particle systems, a swelling pressure term was defined to explain the increase in inter-particle spacing. The swelling pressure was defined as equal and opposite to the capillary pressure tending to force particles to random packing. It was concluded that swelling was related to mass transfer at the solid-liquid interface of the intermetallic crystals giving a reduced static pressure due to a localized minimization of Gibbs energy. The static pressure change (swelling pressure) was attributed to overlap of mass transfer boundary layers where mid-point static liquid metal pressure is less than the pressure in the bulk liquid. For the system studied, the mass transfer boundary layer was estimated to be approximately 100 $ mu$m in thickness. / Further experiments, using the sessile drop technique, were used to support the study findings by showing rapid spreading of liquid lead on Ag-Zn intermetallic substrates. The rapid spreading was attributed to mass transfer at the solid-liquid interface giving a reduced interfacial energy, $ gamma sb{ rm s1}$ due to a localized reduction in Gibbs energy. / The analysis of experimental results led to the development of two new industrial processes in the lead industry aimed at reducing lead loss to silver and bismuth crusts. Tests employing continuous agitation during bismuth removal from lead promoted the growth of large $ rm CaMg sb2Bi sb2$ crystals. The larger crystals minimized the effect of mass transfer boundary layer overlap and reduced lead entrainment from 90 to 80 volume percent. The addition of a low melting point KCl-ZnCl$ sb2$ salt during silver crust formation was found to remove up to 90% of entrained lead by the salt preferentially wetting Ag-Zn intermetallic particles. This was found to eliminate surface forces which retained liquid in the system of solid particles.

Microflotation, laboratory batch, and continuous in-plant minicell tests were conducted to determine if copper ions not only activate sphalerite but also depress pyrite when the minerals are together. / Microflotation was performed on mineral samples over a pH range of 3.5--11. It was found that pyrite recovery increased with addition of copper ions when alone, but decreased by more than 25% (absolute) when sphalerite was also present for the pH range 6--9.5. / Bench flotation tests were performed on Louvicourt Mine ore and Red Dog Mine ore. The results for Red Dog showed that upon addition of copper, pyrite recovery decreased significantly. Pyrite recovery decreased from ca. 70% (no copper) to ca. 10% (4.5 g Cu/kg Zn) at a sphalerite recovery of ca. 70%. / Continuous in-plant minicell tests at Louvicourt Mine also showed that pyrite recovery decreased with addition of copper and further indicated that with excess copper (20 g Cu/kg Zn) pyrite recovery can increase. / The mechanism responsible for the depression of pyrite seems to be competition first for copper then xanthate that favours sphalerite over pyrite. To take advantage of this competition it may be necessary to control the sequence and rate of copper, collector, and lime addition.

The reaction of HCl gas with MgO particles suspended in a molten salt containing magnesium chloride was studied. Chlorination experiments were carried out in a batch stirred tank reactor. The determination of the MgCl2 concentration as a function of chlorination time indicated that the chlorination of MgO to MgCl2 occured through an intermediate step. The intermediate species was assumed to be MgOHCl forming according to the reaction: MgOs+HCl g→MgOHCl d / Alkalimetric titration and thermal decomposition by injection of dry nitrogen were used to confirm the existence of MgOHCl in the molten salt during chlorination. Infrared spectrometry was also tentatively used to identify MgOHCl but, without success due to the hygroscopic nature of the material. / Conventional mass transfer theory was used to develop a model for the reaction of solid MgO particles with HCl dissolved in the molten salt to form MgOHCl. The model assumed shrinking particle behaviour for the MgO and was confirmed by the data from the chlorination experiments. / Moreover, experiments conducted at different HCl flow rates showed that the reaction was controlled by mass transfer of HCl dissolved in the molten salt across the liquid film surrounding the MgO particle to the surface of the particle. The following rate law was obtained CMgOCi MgO1/3=1-K nt the constant Kn was found to vary between 0.04 and 0.08 s-1 when the gas flow rate was varied from 2.5 to 7.5 SLPM at constant temperature and agitation speed of 500°C and 500 RPM, respectively.