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Aluminium-silicon alloys have gained increasing market share in the automotive and aerospace industry because of increased environmental demands. These alloys have a high strength-to-weight ratio, good corrosion resistance, castability and recycling potential. However, variations in properties and limited performance at elevated temperature are restricting these alloys from use at elevated temperatures. During the last decades, researchers have investigated ways to improve the properties at elevated temperatures. However, the effect of some transition elements is not well understood. The aim of this work is to investigate the aluminium-silicon alloys with addition of cobalt and nickel for high temperature applications. Tensile testing and hardness testing were conducted on samples produced by directional solidification in a Bridgman furnace with condition generating a microstructure corresponding to that obtained in high pressure die casting, i.e. SDAS ~ 10 µm. The results show that cobalt and nickel improve the tensile properties up to 230 °C.

The Swedish steelmaking industry produces large amounts of by-products. In 2008, the total amount of slag produced reached approximately 1,300,000 metric tons, of which 20% was deposited. Due to its strength, durability and chemistry, steel slag is of interest in the field of construction, since it has similar or better qualities than ordinary ballast stone, which makes it a competitive construction material. However, some steel slags face an array of quality concerns that might hinder their use. These concerns generally involve the following physical and chemical properties:Volume expansion Disintegration Leaching of metalsBy controlling and modifying process parameters during slag handling in liquid state, the physical and chemical properties of steel slags can be adequately modified to obtain a high-quality product for external application. The present work was undertaken as a research project within the Minerals and Metals Recycling Research Centre, MiMeR. The major goal of this work has been to investigate how different treatment methods including hot stage processing, cooling rates, ageing time and chemical composition influence the final properties of the slag. Analysis techniques used in this investigation include: thermodynamic calculations using FactsageTM, X-ray diffraction analyses (XRD), scanning electron microscopy (SEM), leaching tests (EN12457-2/3) and thermo-gravimetric analyses (TG).The results from this study show that it is possible to control/change the properties of the final product by additions to the liquid slag, thereby changing the chemical composition, as well as by varying the rate and method of cooling. The mineralogical composition, the size of the crystals and the composition of some solid solutions are affected by the cooling rate. The solubility of elements such as chromium and molybdenum varies, probably due to their presence in different minerals. The reactivity of the investigated slag samples increases as the cooling rate increases.When steel slags are aged, the leaching properties of the materials are changed. The total leachability and the pH decrease for all the investigated samples. All elements except magnesium decrease in leachability. As the slags are aged CaCO3 is formed on the slag surfaces. The degree of carbonation differs between different slags, due to the presence of different calcium-rich minerals in the slag. In order to form CaCO3, the calcium-containing mineral must be dissolved. This means that the solubility of the calcium-containing mineral will affect the outcome of the carbonation. The rate of dissolution for six typical slag minerals was investigated in order to distinguish the difference in solubility between the different minerals. Acidic to alkaline pHs (4, 7 and 10) were selected to investigate the solubility of the minerals under conditions comparable to those prevailing in newly produced slags and the potential future pH values obtained under acid conditions. It can be concluded that all six minerals behave differently when dissolving and that the rate of dissolution is generally slower at higher pH. At pH 10, the solubility of merwinite, akermanite and gehlenite is considered slow. The dissolution of γ-Ca2SiO4 is not affected in the same way as the other minerals when the pH is changed. / Godkänd; 2010; 20101213 (fren); DISPUTATION Ämnesområde: Processmetallurgi/Process Metallurgy Opponent: Professor Pekka Taskinen, Dept. of Materials Science and Engineering, Aalto University, Finland Ordförande: Professor Bo Björkman, Institutionen för TKG, Avd för mineralteknik och metallurgi, Luleå tekniska universitet Tid: Fredag den 4 februari 2011, kl 10.00 Plats: F341, Luleå tekniska universitet

Global trends in automotive industry for weight reduction drives an interest for casting of structural aluminum parts. High pressure die casting (HPDC) is chosen for this purpose since it enables manufacturing of large series parts where complexity and repeatability is demanded. Aluminum alloys have hence been developed through the years to obtain suitable mechanical properties for high strength parts. These alloys have been investigated to predict the types of potential failure mechanisms during HPDC in order to determine die life through simulations. Die life prediction was performed through simulations in MAGMAsoft 5.4 with the help of a die life module, which is based on thermal stresses generated in the die material during casting cycles. Fatigue data at elevated temperature obtained from literature review of AISI H11 tool steel was complemented to the Wöhler curve in the software database. Comparison of two aluminum alloys showed that chemical composition had a major influence on die life. Chemical composition had a direct impact on solidification time and with longer solidification time, the thermal load on the die increased. Since the stress range on the die is temperature dependent, the ability of heat transfer over time proved to be critical for die life results. The most crucial process parameter to achieve a longer die life was constant cooling by tempering channels, due to their high potential to remove heat. Tempering channels and die spray also prevent the die from exceeding a critical temperature resulting in soldering formation. Mold erosion was consistently observed in the same location for all simulations.

The constants modernization in the fuels used request improvements in the combustioneffectiveness, as a consequence the material for components as the cylinder heads mustenhance their properties. Seven different compositions of compacted graphite iron (CGI)are analysed with the aim of characterized and select the most suitable material for thecylinder head service condition. The present master thesis report focuses on the impactof the matrix- either pearlitic or ferritic- and alloying elements such as molybdenum andnickel in the fatigue crack propagation ratedadNand fracture toughness (kIc).Tests to determined the fatigue crack growth rate, according to the ASTM standardE647 and fracture toughness (ASTM E399) were conducted. The equipment utilized was aservo hydraulic machine, for the fatigue crack propagation rate test and a electromechanicalmachine for the fracture toughness. Moreover, for measure the crack length a portablemicroscope camera and a camera connected to a DIC(digital image correlation) softwarewas used. The interpretation of the data obtained from the tests were done by TEMA- aDIC software- and MATLAB.The test results are analysed describing the influence of the composition and the microstructurehave over the mechanical properties achieved. Furthermore, an analyse forrelating the graphite average length and the hardness with the fatigue crack growth rateand the fracture toughness of the materials is performed.

The final degree project for a Bachelor of Science in Mining and Mineral Engineering has been carried out at Boliden Mineral AB between April and June 2013.The report describes the history and geology of the mines of Boliden, origin and the development of one of the largest metal-mining companies in Europe - Boliden Mineral AB.In the Boliden area there are many important ore fields which contain gold, zinc, copper, silver and lead.The objective of this project was to investigate and provide the guidelines for the improvement of the regrinding in the ball mill in the Concentrator flotation circuit having influence on metal recovery.The report follows the ore flow from the mine, through the Concentrator and finally to the end product, concentrates. The evaluation leads to conclusions which parameters may affect the concentration process negative.It was discovered that there are problems with the ore stockpiles at the mine and the segregation of the fractions in the silos. It is proposed to install a cone on the top of the silos to reduce segregation of ore fractions. To reduce this problem Boliden should install a mobile conveyor on the way to the silos and to the ore stockpiles in the mine. This method has been successfully installed at the Aitik ore stockpiles near the new Concentrator.The main task of the thesis was to analyze metal distribution in the flotation circuit, especially technical analysis of regrinding effects on the results of flotation. The analysis of the sampled pulp from the flotation process was done in the Mineral Processing Laboratory and in the Process Laboratory in Boliden. The analytical equipment such as X-rays and ICP were used for metal analysis and QEMSCAN was used for mineralogical determinations analyses.Theoretical calculations and results of conducted laboratory experiments suggests that regrinding in the ball mill has a positive effect on the flotation process, but some improvement is required, especially the regrinding of the gangue particles. This process helps to liberate all metal particles and improves results of metal recovery. For improvement of regrinding process, it is proposed to replace the regrinding ball mill with a newer, more efficient mill of SMD type (Stirred Media Detritor). / <p>Validerat; 20131218 (global_studentproject_submitter)</p>

Recent decades have attracted board interest in the Rheocasting process. The High demand for lightweight, strong alloys and complex design parameters involves challenges in maintaining cost-effectiveness and energy consumption. A new rheocasting technique based on Rapid Slurry Formation (RSF), called the RheoMetal™ process enables the manufacture of near net-shaped as-cast components. This research aimed to improve the Rheometal™ process by capacitating the Comptech SLURRYMAKER to improve the microstructural properties and estimate the solid fraction and contiguity as per the process parameters. The influence of slurry preparation parameters, solid fraction, and contiguity on rheological behaviour leads to a variety of viscosity, shear stress, shear rate, yield shear stress, and yield point. The study shows a correlation between control variables of the slurry, which are melt temperature, melt mass, Enthalpy Exchange Material (EEM) addition, EEM diameter, EEM stirring speed, impeller stirring speed, and impeller stirring time against solid fraction and contiguity of the A356 alloy microstructure in the state of Semi-Solid Metal (SSM).

The thesis originates from a need to meet stricter environmental regulations for Scania, to reduce fuel consumption and emission from heavy-vehicles. Scania aims to fulfil these requirements by increasing combustion pressure and temperature. These conditions are tougher for the engine components and they shorten their lifetime. This thesis aims to improve Scania’s ability to increase the lifetime of a heavy-vehicle exhaust manifold, an engine component that collects exhaust from several engine cylinders into one pipe. This was done by conducting a material comparison and a parameter study, both used the FEM software Abaqus CAE. The material comparison consisted of three ferritic and austenitic ductile cast irons (SiMo51, SiMo1000 and Ni-resist) subjected to thermal stress. Their max stress was compared for two thermo-mechanical fatigue cases, out-of-phase and in-phase. A parameter study was also conducted to clarify the influence of thermal conductivity, thermalexpansion, Young’s modulus and yield strength on max stress for OP and IP in the exhaust manifold. The FEM simulation results from the parameter study were used to create functions that can be used to decide how to treat/process a material to minimise the stress in the exhaust manifold. They can also be used in material selection to choose a material that minimises stress. The research questions and their shortened answers can be seen below. 1. Which of SiMo51, SiMo1000 and Ni-resist produces the lowest tensile stresses? ForOP, SiMo1000 produced a slightly lower max principal stress than SiMo51. For IP, Ni-resistproduced the lowest max principal stress by a large margin. 2. How do different material properties affect the maximum stress during operation of thegiven component? Thermal conductivity has a decreasing relation to max stress. Thermalexpansion and Young’s modulus have a similar relation to max stress, stress increases forboth properties as they increase. A decreased yield strength decreases the max stress forstresses above the yield limit but has no effect on stress below it. 3. How should an objective function to minimise max stress in the component with regard to material properties be expressed? functions of OP and IP can be seen in the actual abstract.

3D printing, also known as additive manufacturing (AM), has got rapidly developed since 1987. Compared with conventional manufacturing methods, 3D printing provides some advantages such as increasing material utilization and less waste of material. Maraging steel provides good strength and toughness without losing ductility, which has been used for the 3D printing technique. Selective laser melting (SLM) is one of the 3D printing methods, which is mostly used for metal and alloy powder. In this thesis, selective laser melting will be used for maraging steel. 3D printing maraging steel is a new material, the research about the properties of 3D printing maraging steel is still ongoing. Corrosion resistance is one of the most important properties of maraging steel due to the high cost of corrosion. So this thesis will focus on the corrosion behavior of 3D printing maraging steel. The purpose of this thesis was to find the best heat treatment condition for high corrosion resistance and to find the relationship between microstructure and corrosion behavior of maraging steel. In this thesis, several kinds of maraging steel samples with different heat treatment conditions were used. SLM, SLM austenized&amp;quenched, SLM aged, conventional austenized&amp;quenched, and conventional aged. Besides, two kinds of solutions were produced, NaOH (pH=11.5) and Na2SO4 (pH=6.5). To observe the microstructure, an optical microscope was used. The grain size is different between SLM and conventional samples, and also different between the samples with different heat treatment conditions. The potentiodynamic polarization method was used to measuring the corrosion behavior. SLM samples have much lower current density, and the passivation potential and the corrosion rate are similar compared with conventional samples. But due to the lack of further experiments, the relationship between corrosion behavior could be affected by the combined effect of several factors.

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