There is much that is unknown concerning the creation of Viking age brooches. Recreating these brooches in the same way they would have been created in the Viking age to try to understand how they were created is a time consuming project for experimental archaeologists.   This study has been done in order to find out if the time spent can be reduced and at the same time gain a better understanding of the creation of a Viking age brooch using 3D scanning and computer simulations. Casting simulations of a real Viking age brooch have been done using Magma5, a state of the art simulation software.   Simulations were run with several different casting systems, initial metal and mould temperatures, and both with as well as without the brooches distal figurines attached.   It was found that the initial metal and mould temperatures has got impact on the final result of the brooch, but the alloy and casting system has a much greater effect on the final result. The casting system that yielded the best result has the pouring basin directly above the medial part of the brooch and two sprues leading to gates on the north and south medial sides. / Det är mycket som inte är känt om tillverkningen av vikingatida broscher. Att försöka återskapa dem på samma sätt som vikingarna antagligen skapat dem för att öka kunskapen kring broscherna är ett tidsödande jobb.   Denna studie har gjorts för att ta reda på om den tiden kan reduceras och samtidigt öka kunskapen kring broscherna med hjälp av modern teknik som 3D skanning och datorsimuleringar. Gjutsimuleringar av ett äkta vikingatida spänne har skett i Magma5, ett kraftfullt simuleringsprogram.   Simuleringar utfördes med hjälp av flera olika gjutsystem, stor variation i smältans och formens initiala temperaturer, och både med och utan broschens distal figuriner.   Studien har funnit att smältans och formens temperaturer har påverkan på broschens slutresultat, men legeringen som används och gjutsystemet har betydligt större påverkan på slutresultatet. Gjutsystemet som gav bäst slutresultat har ett inlopp som är placerat direkt över mitten på den mediala delen, och sedan förgrenar sig i två delar och ansluter till den norra och södra delen av formkaviteten.

High Pressure Die Casting (HPDC) has very high demands on toughness and tempering resistance of the tool. A typical hardening cycle for this purpose consists on austenitizing and quenching in a vacuum furnace followed by three temperings at 600°C. In this work the possibility of optimizing the toughness and tempering resistance in Uddeholm Dievar by adding an extra tempering at the beginning and/or the end of the tempering process is investigated. Extra temperings were performed at 300-400° and hardness levels, impact toughness and tempering resistance were evaluated. Microstructural investigations as well as thermodynamical calculations were also carried out. Results showed no feasible differences between the results of the here conducted tests and those from the common tempering procedures.

Phase interface and stacking fault are two common planar defects in metallic materials. In the present thesis, the interfacial energy and the generalized stacking fault energy of random alloys are investigated using density functional theory formulated within the exact muffin-tin orbitals (EMTO) method in combination with the coherent-potential approximation (CPA).The interfacial energy is one of the key physical parameters controlling the formation of the Cr-richα’ phases during the phase decomposition in Fe-Cr ferrite stainless steels. This decomposition is believed to cause the so-called“475°C embrittlement”. Aluminum addition to ferritic stainless steels was found to effectively suppress the deleterious 475oC embrittlement. The effect of Al on the interfacial energy and the formation energy of Fe-Cr solid solutions are studied in this thesis. The interface between the decomposed Fe-rich α and Cr-rich α phases carries a positive excess energy, which represents a barrier for the process of phase separation. Our results show that for the α-Fe70Cr20Al10/α0-Fe100−x−yCryAlx(0≤x≤10, 55≤y≤80) interface, the Al content(x) barely changes the interfacial energy. However, when Al is partitioned only in the alpha phase, i.e. for the α-Fe100−x−yCryAlx/α0-Fe10Cr90(0≤x≤10,0≤y≤25) interface, the interfacial energy increases with Al concentration due to the variation of the formation energies of the Fe-Cr alloys upon Al alloying. The intrinsic energy barriers (IEBs) of the γ surface (also called generalized stacking fault energy, GSFE) provide fundamental physics for understanding the plastic deformation mechanisms in face-centred cubic metals and alloys. In this thesis, the GSFEs of the disordered Cu-X (X=Al, Zn, Ga, Ni) and Pd-X (X=Ag,Au) alloys are calculated. Studying the effect of segregation of the solutes to the stacking fault planes shows that only the local chemical composition affects the GSFEs. Based on the calculated GSFEs values, the previously revealed “universal scaling law” between these IEBs is demonstrated to be well obeyed in random solid solutions. This greatly simplifies the calculations of the twinning parameters or the critical twinning stress. Adopting two twinnability measure parameters derived from the IEBs, we find that in binary Cu alloys, Al, Zn and Ga increase the twinnability, while Ni decreases it. Aluminum and gallium yield similar effects on the twinnability. Our theoretical predictions are in line with the available experimental data. These achievements open new possibilities in understanding and describing the plasticity of complex alloys. / <p>QC 20141104</p>

The research presented in this thesis explores the structure, alloying and stability of the carbides in the Co-Cr-C system by using the CALPHAD approach supported by experimental measurements and ab initio calculations. WC-Co based cemented carbide materials consist of hard WC grains and a ductile Co-based binder. Cr is usually added to cemented carbides for the purpose of reducing grain growth during sintering or to increase corrosion resistance. The Co-Cr-C system is highly relevant for Cr-containing cemented carbides. For example, it determines the allowable C-content interval in the quaternary W-Co-Cr-C system with respect to the formation of unwanted Cr-based carbides. The CALPHAD method is based on critical assessment of model parameters constituting phenomenological expressions of the Gibbs energy and its derivatives, e.g. enthalpy, entropy and heat capacity. A thermodynamic assessment based on the CALPHAD method relies heavily on the available experimental or ab initio calculated information. The crystal structures of Cr23C6 and Cr3C2 have previously been accurately determined. However, various authors reported different crystal structures for the Cr7C3 carbide. A combined experimental and ab initio investigation of the crystal structure of Cr7C3 and M7C3 (M=Co,Cr) was thus performed. Furthermore, the stabilities of all end-member compounds of the mixed carbide at 0 K were determined by ab initio calculations. Available experimental information on phase equilibria with carbides in the Co-Cr-C system was found to be insufficient to describe all the features in the phase diagram. Therefore, the liquid + M23C6 + M7C3 and M7C3 + M3C2 + graphite equilibria (M=Co,Cr) were investigated experimentally with focus on the solubility of Co in the M23C6, M7C3 and M3C2 carbides. Finally, a reassessment of the thermodynamic description of the Co-Cr-C system was performed, which resulted in a set of thermodynamic models and parameters that accurately describe all of the considered information. Applied experimental methods and theoretical models are explained throughout the thesis. Important examples from the appended papers are also given. / <p>QC 20140212</p>

The possibility of cluster formation during solidication of steel is explored to explain structures that are seen on the fracture surface of the steel. A hypothesis is built that postulates porosities provide favourable locations for inclusions to agglomerate and form clusters.  A thermodynamic model is constructed to describe precipitation of porosity and inclusions. Formation of inclusions follow a nucleation and growth mechanism. Porosities on the other hand are the product of pressure balance in the liquid.  Motion of pores and inclusions is analysed based on the drag force and  surface  stresses. Gradient of surface tension is also identied as a driving force which acts on the pore surface and would cause motion. It is shown that relative motion of pores and inclusions coupled with  the inclusion tendency to get attached on pore surface makes or a viable mechanism explaining agglomeration of inclusion particles to clusters / <p>QC 20150930</p>

No description available.

Sanicro 25 is a newly developed austenitic stainless steel, designed for the next generation of Ultrasupercritical coal-fired boilers in electrical power plants. This material is applicable in reheater and superheater tubes, where the material temperature is up to 700 °C. One of the main strengthening mechanisms in high temperature materials is solid solution strengthening. A combination of this mechanism and precipitation hardening, promotes creep strength of heat resistance materials. The aim of this work was to characterize the effects of solid solution strengthening on creep strength of Sanicro 25.Previous works has been done for effects of phosphorous in copper and also for influence of laves phase on the creep properties of CrMo alloys. The results of these two works are used and the model is adapted to austenitic stainless steel. First a Zero starting state was defined which was Alloy 316H and then the calculation was made for Sanicro 25. Thermodynamic calculations were made using DICTRA and Thermo-Calc. Elastic misfit parameter was determined using ab initio calculations. The results from the simulation in this work indicate that solutes with larger size misfit compare to the parent atoms have better solid solution strengthening effect. A decrease in the creep strength by increasing temperature has been observed which could be attributed to growth of laves phase.

The research presented in this thesis investigated the mechanisms by which cavitation erosion damage develops in lamellar graphite iron (LGI) and austempered ductile irons (ADIs). This has been achieved by image sequences of surface erosion on test samples in tandem with weight change measurements. Cavitation erosion is caused by the appearance and collapse of bubbles in a liquid which undergoes rapid pressure oscillations. Imploding bubbles release heat, shockwaves and high-speed microjets which may strike nearby solid walls and damage them. The heavy-duty automotive industry encounters this problem in the engine cooling system. The combustion chamber requires precise temperature control for optimal operation and excess heat must be removed by a liquid coolant. In trucks, the coolant liquid achieves this by circulating around the cylinder liner, a hollow cylindrical part that encloses the combustion chamber and prevents its gases from escaping. However, the engine’s intense vibrations create repeated pressure variations in the coolant, and bubbling ensues. With prolonged operation, the cylinder liner’s wet outer wall may be severely worn, resulting in surface roughening, eroded patches and pits. Cavitation is responsible for great losses due to vehicle downtime and maintenance costs. The present work aims, therefore, at analyzing the behavior under cavitation exposure of cast irons that are currently used, or being considered for use, in the cooling system. Cylinder liners are currently made of lamellar graphite iron with a matrix structure consisting of pearlite and a network of steadite, and the analysis for this material has been presented in Paper 1. Austempered ductile irons are candidate materials for pumps and other components of the cooling system due to their very good mechanical properties; three ADIs of increasing hardness, obtained from different heat treatments of a spheroidal graphite iron, have been analyzed in Paper 2. Experiments consisted of an ultrasonic vibratory probe to which material samples were attached and subsequently immersed in a beaker containing engine coolant. The samples were weighed and photographed in an SEM after several predetermined time intervals. This produced a detailed sequence of images which, in combination with mass loss data, can explain the mechanisms by which cavitation damage initiates and develops in these materials. The text of this thesis summarizes the findings presented in the appended articles and compares the behavior of LGI and ADI. / Forskningen som presenteras i denna avhandling undersöker kavitationsmekanismerna och uppkomsten av kavitationsskador i gjutjärn med fjällgrafit (LGI) och i ausferritiskt segjärn (ADI). Detta har gjorts med sekventiell fotografering av yterosionen på prover samtidigt som viktsförlusten har registre- rats. Kavitationserosion uppstår genom bildning och kollaps av bubblor i en vätska som utsätts för snabba tryckoscillationer. Imploderande bubblor frigör värme, chockvågor och höghastighets- mikrojetstrålar som kan träffa närliggande fasta ytor och skada dessa. Den tunga fordonsindustrin stöter på detta problem bland annat i motorernas kylsystem. Förbränningsrummet fordrar noggrann temperaturkontroll för optimal förbränning och måste kylas av en kylvätska. I lastbilar cirkuleras kylmedlet runt cylinderfodret, en ihålig, cylindrisk komponent som omsluter förbränningskammaren och som hindrar gaser från att lämna systemet. På grund av motorns intensiva vibrationer bildas återkommande tryckvariationer i kylvätskan med uppkomst av bubblor. Efter lång tid i drift kan cylinderfodrets våta utsida bli allvarligt eroderad med ökad ytråhet och med bildande av erosionmönster och erosionsgropar. Kavitation är förknippad med stora förluster pga stillestånd och underhållskostnader. Målet med detta arbete är därför att analysera hur nuvarande, och kandiderande gjutjärn för kylsystem, beter sig under kavitationsexponering. Cylinderfoder görs för närvarande av lamellärt gjutjärn med en matrisstruktur av perlit och ett nätverk av steadit, och en analys av detta material presenteras i artikel 1. Ausferritiska segjärn är kandidatmaterial för pumpar och andra komponenter i kylsystemet pga sina goda mekaniska egenskaper. Tre ausferritiska segjärn med sfärisk grafit och successivt ökande hårdhet, från tre olika värmebehandlingar av samma segjärnsbatch analyseras i artikel 2. Experimenten bestod av ett ultraljudshorn till vilket prover fästes och därefter sänktes ner i en bägare med kylvätska. Proven vägdes och fotograferades i SEM enligt förutbestämda tidsintervall. Detta resulterade i en detaljerad sekvens med bilder som, i kombination med viktsförlusten, kan förklara mekanismerna för initiering och utveckling av kavitationsskador i nämnda material. Avhandlingen summerar fynden som presenteras i de bifogade artiklarna och jämför beteendena mellan LGI och ADI. / <p>QC 20211108</p>

No description available.

The necessity to improve the durability of the machinery used in the milling industry has lead to several types of research. One study is focused on the plates that are located in the stationary and moving jaws of crushers to diminish particles sizes of Gneiss and Diabase rocks. Thus, one type of approach to increase its durability is by reducing the material loss of the plates. Amongst all the parameters to reduce the wear ratio that includes inputs from geometry to load, just the hardness input of the material can be in constant development. Consequently, there are two well-known types of heat treatment that can produce this change in hardness and are named Carbide Free Bainite (CFB) and Quenching and Partitioning (QP). In this master thesis the topic is to perform the QP heat treatments for two compositions A and B to obtain the microstructure of the steels that consist in a mix of austenite, bainite and martensite which considerably increase the hardness while the toughness is not drastically reduced due to the austenite soft phase. Five samples have been studied at four different partitioning temperatures: QP250 A, QP180 B, QP210 B, QP240 B and Mn Steel as it is the composition most used nowadays in the industry. In order to characterise both mechanical properties and microstructural features, different analysis had been performed with Micro-indentations, Charpy-V, Gouging Abrasion Tests, Optical Microscopy, Scanning Electron Microscopy and X-Ray Diffraction. These analysis had been done in the samples before and after wear as a result in change of the microstructure. As the abrasive-impact of the rocks collide with the sample, austenite transforms to martensite by induced plasticity called TRIP effect. Thus, the surface of the alloy is harder than the bulk material as no austenite is found and the wear ratio is seen to be improved. The results have shown several behaviours. Austenite transforms in its majority to fresh martensite which is an unstable martensitic phase but harder than tempered martensite that is the stable martensitic phase. Moreover, the difference in hardness between the bulk and the surface produce an affected depth layer as a consequence of the abrasive-impact penetration of rocks in which the microstructure has fully transformed to martensite on the surface and the austenite phase increases as it goes further inside the steel. The thinner this layer is, the better wear ratio presents the alloy. From all the samples, the best combination of hardness and toughness is for QP210 B.