This project was funded by Automotive Partnership Canada (APC), an initiative created by the Government of Canada in an attempt to support significant, collaborative R&D activities in order to benefit the entire Canadian automotive industry. / High strength Al-Zn-Mg-Cu alloys have been increasingly employed in the transportation industry due to the increased demands for light structural components. However, their applications have been limited to relatively expensive wrought products. Application of the shape cast Al-Zn-Mg-Cu parts has never been the focus of attention due to their poor castability and mechanical properties. Improving the casting quality is expected to increase their utilization within the automotive industry. The poor castability and mechanical properties of some alloys in this family may be effectively improved through optimized chemistry control and melt treatment including grain refinement. The primary objective of this project is to optimize the chemistry and heat treatment of the Al-Zn-Mg-Cu alloy family that results in improved strength with acceptable level of ductility and casting quality relative to other shape cast Al alloys. The Taguchi experimental design method was used to narrow down the number of required casting experiments required to meet the research objective. Three levels across four elements yielded a total of 9 Al-Zn-Mg-Cu alloys, which were cast using a tilt pour permanent mold process. The effect of each major alloying element on the microstructure, and mechanical properties was investigated. Tensile measurements were made on the 9 alloys subjected to two steps solution treatments. Mechanical properties such as yield strength (YS), ultimate tensile strength (UTS), and elongation at fracture (El.%) were experimentally measured and statistically analyzed. An ANOVA analysis was employed to quantify the percentage contribution of the alloying elements on the material properties. Grain refinement was found to play a significant role in improving the hot tearing resistance and, thereby ameliorating quality. The alloying element that affected the YS and UTS to the greatest extent was Cu, followed by Zn. In contrast, the effect of Mg and Ti on YS and UTS was insignificant. Moreover, a decrease in Mg content had the greatest effect in enhancing the El.%. A regression analysis was used to obtain statistical relationships (models) correlating the material properties with the variations in the content of the major alloying elements. The R-square values of YS, UTS, and El.% were 99.7 %, 98 %, and 90 %, respectively, showing that the models replicated the experimental results. Verification measurements made on shape cast Al-6Zn-2Mg-2Cu alloy revealed that the material property model predictions were in agreement with the experimentally measured values. The results show that secondary and over ageing treatments of the shape cast Al-Zn-Mg-Cu alloys lead to superior combination of YS and El.%. The ongoing advances in shape casting of Al-Zn-Mg-Cu alloys with high will make them suitable choices for commercial load-bearing automotive components, when it comes to the selection of a material meeting the minimum requirements for strength, damage tolerance, cost and weight. / Thesis / Master of Applied Science (MASc)

The physical properties of polymer quench bath directly affect the cooling rate of a quenched part. These properties include the type of quenchant, its temperature, concentration, and agitation level. These parameters must be controlled to optimize the quenching process in terms of alloy microstructure, properties and performance. Statistically designed experiments have been performed to investigate the effects of the process parameters (i.e. polymer concentration and agitation) on the heat transfer behavior of cast aluminum alloy A356 in aqueous solution of Aqua-Quench 260 using the CHTE quenching-agitation system. The experiments were designed using Taguchi technique and the experimental results were analyzed with Analysis of Variance (ANOVA) based on the average cooling rate. It is found that average cooling rate dramatically decreases with the increase in polymer concentration. Agitation only enhances the average cooling rate at low and medium concentration levels. From ANOVA analysis, the process parameter that affects the variation of average cooling rate most is the polymer concentration, its percentage contribution is 97%. The effects from agitation and the interaction between polymer concentration and tank agitation are insignificant. The mechanical properties of age-hardenable Al-Si-Mg alloys depend on the rate at which the alloy is cooled after the solutionizing heat treatment. A model based on the transformation kinetics is needed for the design engineer to quantify the effects of quenching rates on the as-aged properties. Quench Factor analysis was developed by Staley to describe the relationship between the cooling rate and the mechanical properties of an age-hardenable alloy. This method has been previously used to successfully predict yield strength, hardness of wrought aluminum alloys. However, the Quench Factor data for aluminum castings are still rare in the literature. In this study, the Jominy End Quench method was used to experimentally collect the time-temperature and hardness data as the inputs for Quench Factor modeling. Multiple linear regression analysis was performed on the experimental data to estimate the kinetic parameters during quenching. Time-Temperature-Property curves of cast aluminum alloy A356 were generated using the estimated kinetic parameters. Experimental verification was performed on a L5 lost foam cast engine head. The predicted hardness agreed well with that experimentally measured.

Thesis (PhD (Chemical Engineering))--Cape Peninsula University of Technology, 2020 / The use of bioproducts in different commercial sectors such as medicine, agriculture, cosmetics, food, and chemical industries motivates the need for easy production and recovery techniques of bioproducts at laboratory and pilot scale. This study aims at the production and recovery of some selected bioproducts using supercritical fluid extraction techniques. Three products are chosen as case studies: these are ethanol, acetoin, and vanillin, since the ease of separation is influenced by the concentration of the product in the broth, these compounds were selected based on their concentration in the fermentation broth, according to literature sources. A standard method was developed in a spectrophotometer for quantifying the targeted product in the broth, while the product recovery studies was carried out using a supercritical fluid extraction pilot plant. Saccharomyces and Bacillus species were chosen for the bioproduction of the selected bioproducts. Experimental design and statistical analysis of results were carried out using response surface methodology (RSM) and artificial neural network (ANN). Studies on each of the selected bioproducts are as justified in the paragraphs below. Bioethanol production has recently become an increasing trend in research, with a focus on increasing its economic viability. Hence, the need to develop a low-cost fermentation medium with minimum redundant nutritional supplements, thereby minimizing the costs associated with nutritional supplements whereby inoculum preparation becomes necessary for ethanol production. Corn steep liquor (CSL) in glucose fermentation by Saccharomyces Type 1 (ST1) strain and Anchor Instant Yeast (AIY), which are low-cost media, are used as replacements for yeast extract (YE). The fermentation process parameters were optimized using artificial neural networks (ANN) and the response surface methodology (RSM). The study shows that for CSL, a maximum average ethanol concentration of 41.92 and 45.16 g/L representing 82% and 88% of the theoretical yield were obtained after 36 h of fermentation in a shake flask for ST1 and AIY respectively. For YE, ethanol concentration equivalent to 86% and 88% of theoretical yield were obtained with ST1 and AIY respectively after 48 h. Although, ANN predicted the responses of ethanol yield better than RSM, optimum conditions for ethanol production were better predicted by RSM. The consumers’ preference for ‘naturally’ produced aromas drives the development of bioproduction of acetoin from glucose with a view to optimize its production. The results revealed that by using a cheap nitrogen source, corn steep liquor, the yield of acetoin was similar to those of yeast and beef extracts. Furthermore, it was shown that by using Box-Behnken design, the optimum parameters such as glucose concentration, corn steep liquor, and inoculum size to maximize the concentration of acetoin produced were 78.40 g/L, 15.00% w/v and 2.70% v/v respectively. The validated concentration of acetoin produced in a triplicate analysis, 10.7 g/L, was 0.06% less than the predicted value. Increasing awareness of consumers of healthy, eco-friendly flavors and fragrances motivates the bioproduction of vanillin. The interactive effects of three variables on vanillin yield were evaluated by response surface methodology (RSM) with Box-Behnken design (BBD) model. The results showed the optimum conditions for the biotransformation of ferulic acid into vanillin can be achieved with maximum overall desirability (D) of 1.0 and a significant (p<0.05) quadratic model with regression coefficient (R2) of 0.995. Corn steep liquor, initial ferulic acid concentration and pH significantly influence the concentration of vanillin in the broth. The results in triplicate experiments confirmed vanillin yield of 386 mg/L after validation, which was in agreement with the prediction of the model. The maximum vanillin yield of 384.40 mg/L was predicted when corn steep liquor, ferulic acid concentration and pH were 7.72 g/L, 2.33 g/L, and 9.34 respectively. Fermentation system in a bioreactor has been proven to be an efficient system for the study of controlled fermentation variables when compared to a shake flask study. The influence of agitation, aeration, time and pH were analysed by Taguchi orthogonal array design for the upscale of acetoin in a bioreactor. The optimized parameters in 1.3L of fermentation vessel were as follows: 300 rpm agitation, 1.5 slpm aeration; 2 days’ fermentation time and 6.5 pH value. Agitation with above 70% was the most contributing factor and other variables were less than 30% in the percentage analysis of variance of each fermentation variables in the batch study of acetoin. A fourfold gain in acetoin titre (42.30 g/L) was obtained with the same substrate concentration in a lab-scale bioreactor on scaling up when compared with the shake flask batch study. The validated acetoin concentration of 41.72 g/L was obtained after a triplicate experiment to confirm the possibility of reproducing acetoin using the optimized conditions. Many separation techniques have been proven to recover value-added products from fermentation broth with a preference for several methods above other and new techniques that are emerging. Supercritical fluids separation using CO2 is one such technique. The feasibility of acetoin concentration and recovery was studied in supercritical CO2 pilot plant with pressure ranges of 100 to 300 bar, CO2 feed rate of 5 to 15 kg/h, at a process temperature of 37 and 80 °C in simulated and fermentation broth, respectively. The validated conditions for the fractionation of acetoin by supercritical fluid extraction (SFE) were determined as follows: extraction pressure, 300 bar; CO2 feed rate, 15 kg/h; extraction temperature 37 °C; and fractionation time of 30 minutes. At these operating conditions, the percentage recovery of acetoin with respect to the feed solution at the raffinate for the simulated and actual ermentation broth was 77.8% (0.20 g/L) and 77% (0.15 g/L) respectively. A two-fold extract increase was obtained after 30 minutes of fractionation. The study provides the technical feasibility and the base case data which are critical to the development and design of processes for production and recovery of acetoin. The lesson gleaned from this study may be extended to develop processes for the production and recovery of other bioproducts (ethanol and vanillin).