Twinning is a known phenomenon in material science, but how is it connected with grain size and yield strength? Investigations are made on alloy 825 with light optical microscopy for 19 samples to calculate the twin fraction and grain size. Afterwards, the results are compared to yield strength throughout tensile tests. The samples have different reduction of dimension by hot rolling and have been annealed for different time intervals. It turns out that twinning makes alloy 825 slightly softer and more ductile on a smaller scale, since the twin fraction increases when the yield strength decreases. However, the grain size also slightly increases when the yield strength decreases, which is important to have in mind for the connection with the three of them. / Tvillingbildning är ett känt fenomen inom materialvetenskap, men hur hör tvillingar, kornstorlek och sträckgräns ihop? Finns det ett samband? Undersökningar utförs med ett ljusoptiskt mikroskop för legering 825 på 19 prover, för att räkna ut tvillingfraktionen och kornstorleken. Detta jämförs sedan med sträckgränsen som man tillhandahåller från dragprov. Proverna har olika reduktion av sin dimension genom valsning och har glödgats olika tider. Det visar sig att tvillingbildning gör legering 825 något mjukare och mer duktil på en mindre skala, eftersom tvillingfraktionen ökar då sträckgränsen sjunker. Dock ökar även kornstorleken när sträckgränsen minskar, vilket är viktigt att tänka på när det kommer till sambandet mellan kornstorlek, tvillingar och sträckgräns.

The Swedish company Azelio has developed a high-efficient Stirling engine which is powered by solar energy. Since the access of solar power is limited to day-time, Azelio has also developed their own Thermal Energy Storage (TES), which collects and stores solar energy and thereby provides the engine with energy also during night-time. The engine runs a generator which produces electricity, around the clock. Liquid sodium is used as Heat Transfer Fluid (HTF) from the TES to the engine, and the temperature reaches above 600°C. At these temperatures, sodium is highly reactive and surrounding materials could strain from phenomena such as corrosion and creep. By comparing the commonly known high-temperature classified steel 253 MA to other commercially available steels, a suitable and affordable option that can withstand liquid sodium is sought. From literature studies, a list of candidates was produced. The materials were then mainly analysed upon ingoing alloying elements’ influence on material properties. The austenitic steel 153 MA has some great advantages to 253 MA at these temperatures, such as a more stable microstructure. 153 MA is therefore, from this work, recommended for further investigation. / Det svenska företaget Azelio har utvecklat en stirlingmotor som drivs av solenergi. Då tillgången på solenergi är begränsad till dagtid har Azelio också utvecklat en termisk lagringsenhet (TES). Den termiska lagringsenheten absorberar och lagrar solenergi och kan därmed förse stirlingmotorn med värme även under natten. Stirlingmotorn driver i sin tur en generator vilken producerar elektricitet under hela dygnet. Natrium används som värmeledningsfluid (HTF) mellan TES och stirlingmotorn, vid temperaturer över 600°C. Vid dessa temperaturer är natrium högreaktivt och fenomen såsom kryp och korrosion kan uppstå, vilka kan påverka egenskaperna hos omgivande material. Genom att jämföra högtemperaturstålet 253 MA med andra kommersiella stål, eftersöks en kvalificerad och prisvärd legering som kan motstå flytande natrium vid dessa temperaturer. Från en omfattande litteraturstudie skapades en lista med möjliga kandidater. Materialen analyserades sedan i huvudsak utifrån ingående legeringselements påverkan på dess egenskaper. Analysen visar på att 153 MA har några betydande fördelar jämfört med 253 MA, såsom en mer stabil mikrostruktur vid de angivna temperaturerna. Detta arbete rekommenderar därför 153 MA för vidare undersökning och testning.

The grain refinement of aluminium by titanium diboride particles, TiB2, using Ti/B grain refiners is common practice in the aluminium industry, but exactly how this grain refinement is achieved is uncertain. Current addition of grain refiner is therefore rarely optimal and excessive addition rates of grain refiner is common. This study investigates grain refinement of aluminium by titanium diboride to create a method and/or model which can be used to aid in addition rate optimisation. The effect of different parameters on grain refinement is the focus and includes cooling rate, properties of the nucleant particles, and growth restriction. A number of experiments using different test methods was applied to investigate this. The study reveals how the parameters investigated affect grain refinement, and how these can be used to optimises grain refiner addition rate. A model aiding in dealing with the varying abilities of nominally identical grain refiners to produce grains is introduced.The conclusion emphasizes the importance of optimising addition rates of grain refiners, for mechanical as well as environmental reasons, and how this can be achieved by changing the investigated parameters. / Kornförfining av aluminium med titandiboridpartiklar, TiB2, genom användning av Ti/B kornförfinare är standard inom aluminiumindustrin. Det är dock inte helt utrett hur denna kornförfining går till. Rådande tillsatsmängder av kornförfinare är därför sällan optimala och alltför stora tillsatsmängder av kornförfinare är vanligt förkommande. Denna studie undersöker kornförfining av aluminium med titandiborid med målet att skapa en metod och/eller modell som kan användas för att underlätta optimering av tillsatsmängder. Fokus ligger på hur olika parametrar influerar kornförfiningen och inkluderar kylningshastighet, egenskaperna hos de kärnbildande partiklarna, och tillväxthämning. Experiment med olika testmetoder utfördes för att undersöka detta. Studien visar hur de undersökta parametrarna påverkar kornförfiningen och hur dessa kan användas till att optimera tillsatsmängden av kornförfinare. En modell användbar för att hantera de skillnader nominellt identiska kornförfinare uppvisar i sin förmåga att producera korn presenteras. Slutsatsen betonar vikten av att optimera tillsatsmängden av kornförfinare, både av materialmässiga och miljömässiga skäl, och hur detta kan uppnås genom ändringar i undersökta parametrar.

A mathematical model based on the continuum mechanic concept has been developed to describe the profile of solid particles in an industrial scale blast furnace. The focus is the in-furnace conditions and its characteristics such as the shape and size of the deadman. The Navier-Stokes differential equation for multi-phase multi-dimensional space has been used to describe the behavior of existing phases. The equation has been modified to make it possible to describe the dual nature of the solid phase in the system. This has been done by applying the concept of the solid surface stress to describe the intergranular surface interactions between particles. More specifically, this term is added as an extra term to the Navier-Stokes equation to describe the particle-particle interactions. This extra term in behave as a breaking force when the particles are sliding down in the furnace. During the descending movement in the furnace it is shown that the particles change their profile from a V-shape to a Wshape, due to the characteristics of the deadman. Moreover, the velocity magnitude is higher at the outer surface of the deadman for higher grid-slabs in this region than the near-wall cells. However, the situation changes as solid particles moving to even lower levels of the grid-slabs at the outer surface of the deadman in comparison to near-wall cells. It has also been shown that an increase in the magnitude of the effective pressure reduces the velocity magnitude of descending particles. Furthermore, since different phases co-exist in a blast furnace, the volume fraction plays an important role in the blast furnace. Therefore, the influence of three different packing densities (0.68, 0.71 and 0.74 respectively) on the profile of the flow through the upper part of the blast furnace from the throat to the tuyeres level has been studied. It is shown that an increase in the volume fraction of the solid phase lead to a decrease in the velocity magnitude. This decrease is due to an increase in the solid volume fraction, which will increase the resident time of the particles inside a blast furnace. In addition, it is shown that the velocity magnitude of the solid phase decreases from the throat to the belly of the furnace, for the studied conditions. However, after belly the velocity magnitude increases again. / <p>QC 20121204</p>

No description available.

The objective of this research is to make a comparison between 2D- and 3D-investigations of non-metallic inclusions (NMIs) in metal samples by different analytical methods. NMIs are undesired particles that degrade the quality of the steel through affecting the mechanical properties. It’s therefor of great importance that NMIs are carefully examined, and the correct investigation method is used depending on what the objective is. The different parameters that were used in this comparison was composition, location, morphology, number and size. The first step in this research was to complete a literature review on the different analytical methods. The examined 2D-methods were ASPEX and INCA Feature, which are automated. The examined 3D-method was electrolytic extraction followed by further examination by SEM, which is a manual examination. The second step was to make an experimental comparison between INCA Feature and electrolytic extraction. It was found that ASPEX and INCA Feature performs well in all parameters except location and morphology, and they are also time-efficient methods. Electrolytic extraction performed well in all parameters but is a time-consuming method. The 2D-methods performs well in the parameters: composition, number and size, and they are also time-efficient. The 3D-method electrolytic extraction is the best when there is a need for a more precise understanding of all the parameters but it’s time-consuming. / Målet med denna undersökning är att göra en jämförelse mellan 2D- och 3D-undersökningar av icke-metalliska inneslutningar (IMIs) i metallprover genom olika analytiska metoder. IMIs är oönskade partiklar som försämrar kvalitén av stålet genom att påverkar de mekaniska egenskaperna. Detta ger oss förståelse att det är otroligt viktigt att noggrant undersöka IMIs och även använda korrekt metod beroende på vad målet är. De olika parametrarna som användes i denna jämförelsen var sammansättning, position, morfologi, antal och storlek. Första steget i denna undersökning var att genomföra en litteraturstudie av de olika analytiska metoderna. De 2D-metoder som undersöktes var ASPEX och INCA Feature, dessa är automatiska. Den 3D-metod som undersöktes var elektrolytisk extraktion där resultatet undersöktes med ett SEM. Denna metod är manuell. Det andra steget var att genomföra en jämförelse mellan INCA Feature och elektrolytisk extraktion genom experiment. Resultatet blev att ASPEX och INCA Feature fungerade väl i alla parametrar förutom position och morfologi och att de även är tidseffektiva metoder. Elektrolytisk extraktion fungerar väl i alla parametrar men är en tidsineffektiv metod. 2D-metoderna fungerar bra när det gäller parametrarna sammansättning, antal och storlek, de är även tideffektiva. 3D-metoden elektrolytisk extraktion är den som fungerar bäst när man behöver få en mer detaljerad och noggrann förståelse för de olika parametrarna men den är tidsineffektiv.

Non-metallic inclusions (NMI) are small impurities that can always be found in steel and other materials. NMIs are of great importance because they may negatively impact various properties of the steel, depending on their composition, morphology and numbers. In the oil and gas industry, one of the most concerning property that can be affected by the NMIs is corrosion resistance. In this report, certain aspects of NMIs were investigated, such as size or composition and effect which they have on the corrosion resistance. To accomplish this, two different steel alloy samples from pipelines were analyzed using electrolytic extraction,a scanning electron microscope (SEM) and a software called ImageJ. The results showed that only Niobium-Titanium carbides (NbTi-C) which were found on one of the samples had the potential to be dangerous, due to them causing pits ranging from 1 to 12.5 times their inclusion size. It was also found out that the size of the inclusions did not affect the size of the pitting that they caused. / Icke metalliska inneslutningar (NMI) är små föroreningar som alltid finns i stål och andramaterial. NMI:er är mycket viktiga eftersom de kan negativt påverka olika egenskaper hos stål, beroende på deras komposition, morfologi och antal. I olje -och gasindustrin är en särskilt oroande egenskap som kan påverkas av NMI:er deras korrosionsmotstånd. I denna rapport undersöktes hur olika aspekter hos NMI:er, som storlek eller komposition, påverkade korrosionsmotståndet i rostfritt stål. För att utföra detta analyserades två olika stållegeringsprovbitar från pipelines med elektrolytisk extraktion, ett svepelektronmikroskop (SEM) och ett program som kallas ImageJ. Från resultatet framkom det att baraNiob-Titankarbider (NbTi-C) som fanns på en av provbitarna hade potentialen att vara farlig, då den orsakar gropar som är 1 till 12.5 gånger större än sin egen storlek. Det framkom också att storleken på inneslutningarna inte påverkade storleken på deras gropar.

Nickel-based superalloys have a wide range of applications, mainly in gas turbines for power generation and aircraft propulsion. They are superior to competing alloys in maintaining excellent mechanical properties for extended durations at extreme temperatures and loads, all while resisting corrosion and oxidation. Haynes 282 is a new age-hardenable nickel-based superalloy that is reported to have a remarkable combination of creep strength, thermal stability, weldability and formability that gives it potential for new applications. Additive manufacturing (AM) is often referred to as 3D printing and the term comprises a number of techniques with the commonality of producing components layer-by-layer with a 3D CAD model as basis. The AM methods allow for unprecedented design freedom and the possibility of replacing complex multi-part components with single part components. The AM methods also enable shorter lead times in many cases and repairs where only part of a component can be replaced instead of replacing the whole component. Selective laser melting (SLM) is a metal AM method that involves a metal powder bed and a laser beam that fuses the powder by melting it according to the predefined geometry. The aim of this project was to evaluate the effect of different heat treatments for Haynes 282 components produced by SLM and it was done by microstructural studies and mechanical testing. Comparisons were made between literature reports on the conventionally produced material, the as-manufactured SLM material and three different heat treatments of 1120-2h-WQ+1010-2h-AC+788-8h-AC, 1170-8hWQ+1010-2h-AC+788-8h-AC and 1170-8h-WQ+1010-4h-AC+788-8h-AC. The first one is recommended by Haynes for conventionally produced material. The microstructural studies focused on identifying occurring phases and their distribution. The grain boundary carbide precipitation after heat treatment was shown to be rather different from the conventionally produced material both in terms of carbide types and their distributions. Grain boundary carbide networks were formed after all the heat treatments. A fine intragranular distribution of a titanium-rich phase that could not be identified was found in all examined SLM specimens. The mechanical testing consisted of tensile testing at room temperature and 600°C, impact testing and hardness testing. The heat treated specimens exhibited remarkable strength but significant embrittlement that was believed to be caused by the grain boundary carbide networks.

This thesis investigates the influence of pulsing on the mechanical properties of PVD TiAlN coatings. The thesis focuses on defects caused by droplets during the arc-evaporation technique by altering the duty time, which affects mechanical properties. The coatings' properties and performance depend on the microstructure and morphology, which, in turn, depend on the process parameters of the PVD process. The methodology used to analyze the coatings included microscopy techniques such as SEM and EDS. The study found that coatings produced using pulsed bias exhibited a considerably higher number of droplets, i.e. the rounded topography, than those produced using DC bias. The duty cycle of the pulsed bias may play a significant role in determining the surface characteristics of the coatings, where pulsed bias coatings with a 10% duty cycle resulted in rougher surfaces, while a 20% duty cycle resulted in smoother surfaces. The surface composition of the coatings exhibits high consistency, characterized by an even distribution of titanium and elevated concentrations of aluminum and nitrogen on droplets from both methods. A higher duty cycle also led to more cracks in the coating. / Den här arbetet undersöker påverkan av pulsering på de mekaniska egenskaperna hos PVD TiAlN-beläggningar. Studien fokuserar på defekter orsakade av droppar under arc-förångning genom att ändra dödtiden, vilket påverkar de mekaniska egenskaperna. Beläggningarnas egenskaper och prestanda beror på mikrostrukturen och liknande karaktärsdrag, som i sin tur beror på processparametrarna för PVD-processen. Metodologin som användes för att analysera beläggningarna inkluderade mikroskopitekniker som SEM och EDS. Studien visade att beläggningar som producerades med pulserad bias hade betydligt fler droppar än de som producerades med likströmsbias. Pulserad bias arbetscykel kan spela en betydande roll för att bestämma ytegenskaperna hos beläggningarna, där beläggningar med en duty cycle på 10% resulterade i grövre ytor, medan en duty cycle på 20% resulterade i jämnare ytor. Ytkompositionen hos beläggningarna uppvisar hög konsekvens, kännetecknad av en jämn fördelning av titan och förhöjda koncentrationer av aluminium och kväve på droppar från båda metoderna. En längre arbetscykel ledde också till fler sprickor på beläggningen.

Novel solar cells are being synthesized from sustainable, non-toxic, and economic materials. All metal oxide semiconductors are one such class of these materials. Synthesis of different combinations of p and n type MO semiconductors heterojunctions as well as high throughput characterization is crucial to improve their applications in fields such as solar cells. A Cu2O/TiO2 Nanorods heterojunction is synthesized on a fluorine doped tin oxide substrate. The TiO2 Nanorods are synthesized via a two-step, solvothermal method. The Cu2O is deposited conformally on the TiO2 NRs via a physical vapor deposition method known as RF magnetron sputtering, with thicknesses of 100, 50 and 25 nm. Characterization methods are used to first determine that the correct materials were synthesized and deposited. Scanning electron microscopy demonstrated that nanorods were made of length, 750 nm, and width, 45 nm. Optical measurements were taken, including: absorbance, transmittance, and reflectance; trends followed the optical data as the thickness of the p-type material increased. From the absorbance data, the bandgap of the materials could be calculated from the generated Tauc plot. The bandgap of TiO2 was calculated to be 3.0 eV which agreed with literature values. The bandgap of Cu2O was calculated to be 2.76 eV which is not in agreement with literature values. X-ray diffraction demonstrated that TiO2 rutile phase was grown, with diffraction angles at: 36.45, 62.747 and 69.766 with their lattice planes being (011), (002) and (112) respectively. Raman spectroscopy demonstrated TiO2 in the rutile phase with Raman shifts at both 447 cm-1 (Eg) and 609 cm-1(A1g). There is a minor peak at 522 cm-1 (T2g) which correlates to Cu2O. Macro-electrical measurements were taken to plot a current vs voltage curve (IV curve), under dark and light conditions. From the macro-electrical measurements Isc, Voc and η (photoconversion efficiency) were calculated: 2.38 E-09 A, -0.18 V, 7.25E-07 respectively (under light, 1 sun equivalent). Atomic force microscopy (AFM) was used to attain topographical images, force/deflection curves, IV curves/maps, and surface potential maps. Conductive-AFM (c-AFM) and Kelvin Probe Force Microscopy (KPFM) were the specific AFM techniques used. From the KPFM measurements it was possible to measure the work functions of TiO2 NRs and Cu2O/TiO2 NRs by using highly oriented pyrolyzed graphite as a reference. The work function for TiO2 NRs was: 4.24 eV and 4.14 eV under dark and light conditions respectively. The work function of the 100 nm Cu2O/TiO2 NRs heterojunction was 4.44 eV and 4.35 eV under dark and light conditions respectively. The apparent work functions that were calculated via this KPFM method were not in agreement with literature values of the respective materials. This thesis has proved that Cu2O/TiO2 Nanorod Heterojunctions can be synthesized using previously known solvothermal synthetic methods. Furthermore these Cu2O/TiO2 Nanorod Heterojunctions have an increase in current under illumination. This current response under illumination has been studied on the nanoscale, using KPFM and C-AFM, as well as on the macroscale. Further investigations on the nanoscale are to be done, which can shed light on how and why these all metal oxide nanorod heterojunctions are functioning as solar cells.