Rozprawy doktorskie: „WELD METALLURGY”

1

Flores, Torres Santiago. "Characterisation of weld-features in RR1000 inertia friction welds". Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8389/.

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This thesis is an investigation into a family of features that can form during the inertia friction welding of the nickel-based superalloy RR1000. A thorough characterisation of the weld features using scanning-electron microscopy has been carried out, yielding information about their composition, microstructure, morphology and their distribution within the weld zone.

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Sugden, Alastair Allen Brockbank. "Towards the prediction of weld metal properties". Thesis, University of Cambridge, 1989. https://www.repository.cam.ac.uk/handle/1810/221892.

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McRobie, D. E. "Cleavage fracture in C-Mn weld metals". Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355272.

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Reed, Philippa Ann Sarah. "Effects of warm prestressing on A533B weld metal". Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334223.

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5

Babu, Sudarsanam Suresh. "Acicular ferrite and bainite in Fe-Cr-C weld deposits". Thesis, University of Cambridge, 1991. https://www.repository.cam.ac.uk/handle/1810/221886.

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Lee, Taeseon. "Impact Welding: Fundamental Studies on Weld Interface Structure". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1543493357444402.

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Reed, Roger Charles. "The characterisation and modelling of multipass steel weld heat-affected zones". Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334220.

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rudow, matthew. "Effect of Oxidation on Weld Strengthof Dissimilar Resistance Weld Interface Between 304 Stainless Steeland Near Equiatomic Austenitic Nitinol Guide Wire". DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/855.

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Abbott Vascular encountered strength and variability issues when attempting to resistively weld 304 Stainless Steel to equiatomic Nitinol. Initial observations suggested that passivation layer (Cr2O3, TiO2) formation affected the weld interface. One hundred 304 Stainless Steel/Nitinol pairs were allowed to oxidize in air at room temperature for allowed periods of time (.1, 1, 3, 5, 7, 12, 16, 24, 168, and 336 hours). Each pair was welded resistively with constant current. A Miyachi/Unitek Advanced Data Analysis Monitor (ADAM) recorded the peak resistance at the instance the weld was made. Resistances were compared to Instron 5900 tensile maximum break load (KgF). Use of optical microscopy and Scanning Electron Microscopy (SEM) revealed microstructural reduction of void size at the sample fracture surface (1-.5 µm). Literature suggested the existence of metastable precipitate forms at near equiatomic compositions within the theoretical temperature range (261.9-1425.2 0C). The Instron 5900 mechanically validated presence of precipitates, while Electron Dispersive X-Ray Spectroscopy (EDS) confirmed the existence compositionally. Literature confirms B19’ precipitates size increases with temperature. This suggests higher resistance samples will promote growth of precipitates due to increased heat input. Increased average particle size was observed with increased resistance (0-.3 µm). Crystal lattice inconsistencies between Nitinol parent phase (B2) and B19’ promote premature fracture due to increased misfit dislocation density. Therefore increased weld resistance promotes the growth of incoherent Ti3Ni4 precipitates which inhibit load bearing capabilities, causing premature failure.

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Hodgson, David K. "The Post Weld Heat Treatment Response in the Heat Affected Zone of 2.25Cr-1Mo Steel". The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1367416587.

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Maier, Petra. "Segregation behaviour of phosphorus, manganese and carbon in boiler shell weld materials". Thesis, Loughborough University, 2002. https://dspace.lboro.ac.uk/2134/35335.

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The work in this thesis has developed theoretical models to predict the microstructural behaviour of weld materials. Three different types of boiler shell weld materials from nuclear power plants have been investigated. The materials considered differ mainly in the manganese concentration and their microstructure after different temperature exposures during industrial use. Element segregation can be predicted according to the typical reactor conditions and therefore the influence of longer life times can be evaluated. Sufficient experimental data have been taken by application of advanced transmission electron microscopes which offer images of high quality. The application of a thermodynamic software package MTDATA to predict the free concentration of each element for model prediction has been. Phosphorus, of great interest because it causes embrittlement, is enhanced at the grain boundary and increases with operating temperature and life time. Its interaction with carbon and manganese is of interest. Site-competition between carbon, phosphorus and manganese has to be applied. These site competition model prediction results fit best to the experimental data.

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11

Wildash, Clint. "Microstructure factors affecting hydrogen induced cold cracking in high strength steel weld metal". Thesis, University of Leeds, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364642.

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McFarland, K. W. "Fissure and chevron crack formation in SD2-3% nickel steel submerged arc weld deposits". Thesis, Cranfield University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376196.

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13

Andersson, Jim. "Manufacturing of Welded Rings : Evaluation of Post-Weld Operations". Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-74578.

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Pipe and ring blanks can be produced in several different ways. Today's focus on environmental effects motivates companies to develop processes that are as efficient as possible in their production. Ringsvets AB is a company that produces pipe and ring blanks from a flat stock by rolling and welding the piece to make it stay in its desired form. The direct benefit of the method is the minimizing of material loss, and it has thereby both environmental and economical advantages. The downside of the method is that the processes involved changes the mechanical behavior of the ring, locally around the weld zone. The focus of this master thesis is the processes and how they affect the material, both microstructure and behavior. The processes involved are; rolling, welding, shaping, brushing, forging, heat treatment, and calibration. The purpose of this work was to elevate the knowledge and understanding of the processes at Ringsvets. The goals were to give a theoretical description of them along with practical test results and explanations of how and why they function in reality. A literature study has been conducted which provided a theoretical basis on how the material reacts on certain processes. Practical examination of samples from current production has been done to get evidence of how well the processes are used, and how well they function, in today's production. Lastly, the main focus of the thesis, an evaluation has been made; do theory and practice correlate, and should anything be changed to correlate better? The results showed that the first operations do not alter the material behavior to an unacceptable extent. Forging, on the other hand, gives the material a very high hardness in the weld zone, and that needs to be corrected. The following heat treatment should compensate for that in a perfect world, but does not in reality. The finished ring shows good properties in general but with places where the heat treatment has failed to correct the uneven behavior induced by earlier operations. The heat treatment requires some adjustments before it functions as intended. Some grainshas not been recrystallized which makes them very hard and non-ductile. Future tests using a higher temperature or a longer heat treatment time would reveal the best way to adjust the heat treatment to obtain the desired properties. Other changes in the processes could also be benecial. Interesting things to try and change would, for example, be the degree of deformation in the forging, which affects the recrystallization temperature. Notes should be taken that this examination is done on just one sample of just one size. Analyses of different samples of different sizes should be done to ensure of the accuracy of the examination.

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14

Champagne, Matthew. "Investigation of 2195 and 2219 Post Weld Heat Treatments for Additive Friction Stir Lap Welds". ScholarWorks@UNO, 2017. https://scholarworks.uno.edu/td/2402.

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To evaluate potential uses for friction stir welding in additive manufacturing, two separate parts were fabricated, one of 2195-T84 and the other 2219-T87, utilizing fixed pin techniques and additive lap welds. The parts were cut into samples, artificially aged and subjected to Rockwell hardness (HRB), Vickers hardness, micrographic photography, and metallographic imaging on both pre- and post- heat treatment. Additionally, tensile testing was performed on the heat-treated samples. A comparisons of test results showed a minimal increase in the yield strength of the 2195-T84 samples compared to as-welded tensile results obtained from a previous project. The ultimate tensile strength was reduced by approximately 16%. Further testing will be required to determine the nature of this reduction. No previous results were available for the as-welded 2219-T87, but UTS of the artificially aged samples was approximately 91% that of the parent material.

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15

Rafferty, John Gerard. "Robust weld quality : a quality system model for welding engineering and fabrication methodology in the petrochemical, process, structural and offshore industry sectors". Thesis, University of the West of Scotland, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244009.

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16

Kimpton, Claire Michelle. "Effects of post weld heat treatments on the fatigue of the inertia welded nickel based superalloy RR1000 at high temperatures". Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/1326/.

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To improve the efficiency of turbine aero engines, higher operating temperatures and weight savings are being investigated. Alloys such as RR1000 are being trialled as they perform better at higher temperatures than current nickel-based superalloys. To achieve weight savings, inertia welding is being trialled for turbine discs but current post weld heat treatments reduce fatigue life. In this investigation, a number of novel post weld heat treatments were trialled aimed at improving post weld microstructure and fatigue properties. Extensive microstructural characterisation and mechanical testing were used to assess the effect of these treatments on both parent and weld materials. Post weld heat treatment (PWHT) was found to have a great effect on the size and distribution of γ' and carbides, particularly when a PWHT temperature of 980ºC or above was used. The effect of this microstructural change on the hardness of the weld and parent material has also been characterised. Extensive total life fatigue testing was carried out at 650ºC. It was found that failure can occur in both the parent and weld material, although it is deduced that the yield stress of the weld needs to be surpassed to see weld failure (plasticity in the weld). Increasing dwell time at peak load reduced the life of these components. Two mechanisms for crack growth were observed with initiation either at the surface or at a large Hf rich particle subsurface. Oxidation was found to have a large effect on both initiation and growth of fatigue cracks. By introducing a sharp pre-fatigue crack into samples, static load testing was used to determine a threshold value of K (stress intensity factor) for growth and growth rates were plotted at different K values. It was seen in these tests that PWHT had a large effect on growth rates and threshold values of K.

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Narayanan, Badri Kannan. "Effect of Alloying on Microstructure and Precipitate Evolution in Ferritic Weld Metal". The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243965903.

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18

Sutton, Benjamin James. "Solidification Behavior and Hot Cracking Susceptibility of High Manganese Steel Weld Metals". The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366302517.

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Alexandre, Rex T. "Induction Bending of Internally Clad Steel Pipes: Failure Mechanisms & Processing Parameter Optimization in Ni-base Alloy Weld Overlays". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480422106975311.

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20

Du, Plessis John. "Control of diffusible weld metal hydrogen through arc chemistry modifications". Diss., Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-05152007-131110.

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Pitrun, Miroslav. "The effect of welding parameters on levels of diffusible hydrogen in weld metal deposited using gas shielded rutile flux cored wires". Access electronically, 2004. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20050202.153920/index.html.

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Luskin, Timothy Clark. "Investigation of Weldability in High-Cr Ni-base Filler Metals". The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366210427.

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23

Wheeling, Rebecca Ann. "Eutectic Backfilling: A Fundamental Investigation into Compositional Effects on the Nature of this Crack Healing Phenomenon for Ni-30Cr Weld Applications". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1523349907312233.

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24

Nissley, Nathan Eugene. "Intermediate temperature grain boundary embrittlement in nickel-base weld metals". Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1156949345.

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Gould, Elijah Katunich. "Development of Constitution Diagram for Dissimilar Metal Welds in Nickel Alloys and Carbon and Low-Alloy Steels". The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1285007217.

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Eksi, Murat. "Optimization Of Mechanical And Microstructural Properties Of Weld Joints Between Aluminium-magnesium And Aluminium-magnesium-silicon Alloys With Different Thicknesses". Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615649/index.pdf.

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For the last decades usage of aluminium alloys have been increasing tremendously. They have been used in aerospace industry widely and now aluminium alloys are becoming more and more popular in automotive and defense industries. Consequently
successful welding of aluminium alloys gains importance. In this study a research is carried out on eldability of plates having different thicknesses of composition 5754 aluminium and 6063 aluminium in T-fillet geometry using Gas-metal Arc Welding technique. It was aimed to have a successful joint without using pre-weld and post-weld heat treatments. During tests welding current and voltage were the varying parameters as welding speed was held constant. Macro-examinations were performed to see the penetration of the weld metal. It was seen that the type of filler wire greatly effects weld penetration. Hardness tests, tensile tests were done to compare the mechanical properties of the welded joints with different filler wires. Despite having better penetration in 4043 filler wire used weld joints, 5356 filler wire used weld joints had higher tensile strength and ductility. In the second part of the study, a dynamic loading machine was designed and manufactured to see the behavior of the fillet welds under dynamic loading. The amount of stress and strain given to the specimen on this machine was adjustable but can&rsquo
t be measured. The tests that were made with this machine aimed only to compare the number of cycles of specimens before fracture. For dynamic loading tests two groups of specimens were prepared with filler wire 4043
each group having been welded with different heat inputs. It was aimed to see the effect of welding heat input on service lifes but no significant difference between cycle numbers of specimen groups having been welded with different heat inputs was observed. Microstructure examinations of these specimens revealed that coarsening the grains, grain boundaries, particles in PMZ and HAZ regions between Al 6063 base metal and weld zone made these areas more susceptible and favorable for crack propogation than Al 6063 base metal.

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Semple, Jennifer K. Semple. "Pedigreed Material Property Data for Residual Stress and Distortion Modeling of Naval Steel Weldments". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1533813179740352.

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Mahaffey, David. "Inertia Friction Welded Ni-Base Superalloys: Process Examination, Modeling and Microstructure". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1462525317.

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Suh, Sanghyun. "Weldability Evaluation in Autogenous Welds of Alloys 230, 800H, and 825". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471581194.

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Race, Julia Margaret. "Carbon diffusion across dissimilar steel welds". Thesis, University of Cambridge, 1992. https://www.repository.cam.ac.uk/handle/1810/221881.

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Dai, Tao Dai. "Effect of Postweld Heat Treatment on the Properties of Steel Clad with Alloy 625 for Petrochemical Applications". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1523572474171801.

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Choudhary, Habib Ullah. "Anomalous behaviour of molybdenum in steel welds". Thesis, University of Cambridge, 1993. https://www.repository.cam.ac.uk/handle/1810/219195.

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The addition of molybdenum to steel welds in quite small concentrations leads to a variety of anomalous microstructural and mechanical property effects. In some cases, the effects manifest even when there are no obvious changes in microstructure at the resolution of a transmission electron microscope. There are two particular discrepancies. A quantitative analysis of molybdenum-containing steel welds indicates that there is a degree of strengthening which cannot be explained by the known solid solution or microstructural effects of molybdenum in steels. Secondly, in multirun welds, the addition of molybdenum appears to make the microstructure which evolves during solidification (the primary microstruet1lre) extremely stable. These and other associated phenomena are examined in this thesis. The molybdenum effects mentioned above have been reproduced in detail, using a series of 'high-purity' multirun welds. Having confirmed that molybdenum increases the fraction of primary microstructure in such welds, an attempt was made to see whether the effect is attributable to a change in the austenitisation characteristics with alloying additions. Extensive work using dilatometric techniques backed by microscopy analysis has demonstrated that molybdenum does not lead to any substantial or unexpected changes in the ability to form austenite. The second hypothesis, that the primary microstructure is stabilised as molybdenum increases the tempering resistance, is proven and provides a good explanation of the observations. A series of tempering experiments have established that the anomalously high strength of the molybdenum containing welds cannot be attributed to solid solution strengthening or microstructural effects. Indeed, it appears that there is a submicroscopic secondary hardening type effect which enhances the strength. Even the thermal treatment that occurs as the weld cools from the solidification temperature is shown to be sufficient to induce molybdenum based secondary hardening type effects. Some preliminary atomic resolution effects also lend support to this concept. Titanium as a trace element is important in steel welds, as an element which promotes the intragranular nucleation of acicular ferrite on titanium-rich phases. It is demonstrated that the titanium effect is not intrinsically different for molybdenumcontaining welds. However, the extra hardenability associated with molybdenum certainly helps to suppress the formation of other grain boundary nucleated phases which might swamp events that occur on the inclusions within the grains. An interesting observation is that titanium has a positive effect in limiting the grain boundary nucleated phases, because the intragranularly nucleated acicular ferrite to some extent stifles the formation of other phases.

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Stevens, Peter Alastair. "Shear zone properties of inertia friction welds". Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5770/.

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Inertia weld process variables arc characterised using empirical relations that arc functions of the weld input parameters, allowing the variables to be predicted for any future production welds. The techniques for establishing the empirical relations can be applied to future alloy system for inertia welding by using significantly refined test matrices, reducing the development costs of new welds. Power loss in the bearings for two inertia welding machines is characterised by using hydrostatic bearing theory and several experimental techniques. This allows energy-based empirical relations for new alloy systems to be developed using sub-scale welds only, reducing the cost of implementing future production welds. Average temperature and now stress of the plasticised zone of welds is used to characterise the average shear zone thickness. Two separate models arc developed and arc found to correlate well with each other and with experimental observations. This work helps to improve the mechanistic understanding of inertia weld interfaces and can be used in computational fluid dynamics models to characterise the bond-line cleaning mechanism.

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Haddad, Naseem Issa Abdallah. "The development of microstructure in duplex stainless steel welds". Thesis, University of Cambridge, 1990. https://www.repository.cam.ac.uk/handle/1810/221890.

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Hall, Bruce Eric. "The microstructure and properties of laser welds in steels". Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334008.

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Mirza, Rashad Mahmood. "Determination of low levels of diffusible hydrogen in steel welds". Thesis, University of Leeds, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342396.

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37

Lawson, Benjamin James. "Compositional Optimization, Mechanical Properties, and Tempering Response in Type 410 Stainless Steel Welds". The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1557201840078564.

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Attallah, Moataz. "Microstructure property development in friction stir welds of aluminim based alloys". Thesis, University of Birmingham, 2008. http://etheses.bham.ac.uk//id/eprint/1024/.

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Friction Stir Welding (FSW) is known to result in a complex microstructural development, with features that remain unexplained, such as: the formation of the onion rings structure. Moreover, various microstructural factors have been suggested to control the strength in Al-Mg AA5xxx welds. The influence of the basemetal microstructural parameters (e.g. grains, intermetallic particles, stored energy) on the microstructure-property development has not been previously investigated, and is the subject of the present work. To rationalise the microstructural and local strength (hardness) development, especially within the heat affected zone (HAZ), a simple and rapid 3-D heat transfer model was established to predict the thermal fields associated with FSW. This numerical model utilises the alternating direction implicit method to simulate the transient thermal cycle based on the process parameters, thermo-physical and thermo-mechanical properties of the material. The model was fitted for the friction coefficient and contact conductance between the sheet and the backing plate using experimental torque and force data, as well as in-situ thermocouple measurements for AA2xxx and AA5xxx welds. The model predictions were consistent with the microstructural and microhardness development in the welds. Gleeble thermal simulations showed that the heating rate during welding affects the recrystallisation start temperature, which could delay or speed up recrystallisation. In the thermo-mechanically affected zone (TMAZ), the onion rings structure was studied in several AA5xxx and AA2xxx welds. This follows a thorough microstructural investigation of the basemetals sheets prepared by direct chill and continuous casting, to establish the influence of the microstructural heterogeneity in the basemetal on the onion rings formation and the microstructural development. Stereological studies of the intermetallic particle distributions in the basemetal and the welds revealed that there is a direct relation between the banding of constituent particles (Al(Fe,Mn)Si or Al6(Fe,Mn) in AA5xxx) or equilibrium phases (Al2CuMg or Al2Cu in AA2xxx) along the rolling direction, and the formation of the onion rings. A clear onion rings structure was defined by three microstructural features, which are: 1) the existence of fine and coarse grain bands, 2) grain boundary precipitates coinciding with the fine grain bands, and 3) coarse particle segregation in the coarse grain bands. Upon etching, these microstructural heterogeneities form the unique onion rings etching profile. The formation of the onion rings was rather independent of the process parameters and alloy type, as long as the intermetallic particles are banded regardless of their types. However, alloys with high area fraction of intermetallic particles (~> 0.02) were found to produce more pronounced microstructural heterogeneities, which resulted in a stronger etching intensity. The microstructural heterogeneities within the AA5xxx welds, especially the interaction between the dislocations and the fine Al6(Fe,Mn) dispersoids, indicated that establishing a structure-property model requires the incorporation of the various strengthening factors. Stereological studies of the grain size and intermetallic particle distributions in the TMAZ indicated that the hardness is a combination of various microstructural factors, with grain-boundary strengthening as the main factor, with additional contributions by Orowan strengthening by the Al6(Fe,Mn) particles in specific locations, as well as a minor contribution by solid solution strengthening which resulted from the dissolution of Mg2Si during welding. The high dislocation stored energy in the TMAZ, as measured by differential scanning calorimetry, was associated with the geometrically-necessary dislocations which resulted from the interaction with the intermetallic particles and grains, but do not contribute to the hardness.

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Kim, Yeong Ho. "Chromium-free consumable for welding stainless steel corrosion perspective /". Columbus, Ohio : Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1133285376.

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Whitaker, Iain Robert. "The structure and properties of autogenous laser beam welds in aluminium alloys". Thesis, University of Nottingham, 1994. http://eprints.nottingham.ac.uk/28427/.

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Autogenous laser beam welds were made in sheets of the aluminium alloys 8090, 8009 and 6061. The Al-Li based alloy 8090 was subjected to both continuous wave CO2 and pulsed Nd:YAG thermal cycles with average powers of 1.5-3.8 kW and 0.8- 0.9 kW respectively. The two techniques were compared for their influence on the 8090 solidified weld pool shape, the fusion zone microstructure and microhardness, the HAZ and the susceptibility of the fusion zone to post-weld heat treatment. It was found that CO2 keyhole welding is preferable to Nd:YAG welding, under the welding conditions investigated, as essential elements such as Li and Mg were lost by evaporation during Nd:YAG processing. Microscopy of the 8090 CO2 weld fusion zone revealed that the solidification mode was sensitive both to the temperature gradient and growth rate during solidification, with a transformation from cellular to equiaxed dendritic growth occurring from the weld pool edge to the weld centre. The secondary dendrite arm spacing was found to be 2-5µm and the metastable phase δ (Al3Li) was present after welding with a very fine homogeneous distribution of -5nm diameter spheres. Porosity was identified as a major welding defect and was attributed to two distinct formation mechanisms. Firstly, the release of hydrogen gas during welding caused spherical gas bubbles throughout the weld pool. Secondly, the delicate balance of forces within the keyhole resulted in larger irregular shaped pores at the weld centre-line towards the weld root. This second type of pore was virtually absent in full penetration welds. The influence of heating rate to the solution treatment temperature on 8090 CO2 weld metal was assessed and the weld metal grain size was found to be most uniformly small after a heating rate of 1 K/min. A TEM investigation confirmed that the grain boundary pinning dispersoid β(Al3Zr) was responsible for inhibiting grain growth. However, the microhardness and notch-tensile strength of the CO2 weld metal did not depend on the weld metal grain size. Instead, it was suggested that the residual cast structure was responsible for determining the mode of failure and fracture strength. Microstructural studies of CO2 laser welds in RSIPM 8009 and wrought 6061 confirmed the cooling rate of 102-103 K/s predicted for CO2 welds in 8090. However, the 8009 CO2 weld metal did not solidify by epitaxial growth from the fusion boundary, which was the case for CO2 welds in 8090 and 6061. Instead, solidification in 8009 weld pools occurred via many isolated events on primary intermetallic particles. The intermetallic particles had the stoichiometry Al4.5(Fe,V,Si) with the AI.mFe tetragonal lattice parameters. It was qualitatively shown that the 8009 weld microhardness had an inverse relationship with the volume fraction of intermetallic particles. Chemical analysis of the 6061 weld metal confirmed that even when aluminium is alloyed with volatile elements such as Mg it is mostly retained within the weld pool during CO2 keyhole laser welding. It was found that a much higher power was required to obtain a deep penetration weld in 6061 than in either of the other alloys.

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Jones, Stephen John. "Modelling inclusion potency and simultaneous transformation kinetics in steels". Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245152.

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Baker, Sarah. "Investigating the process-microstructure-mechanical property development in Ti-6AL-4V friction stir welds". Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6057/.

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The aim of the work reported in this thesis is to develop friction stir welding for superplastic titanium alloys. A number of studies have shown that friction stir welding is capable of retaining the fine-grained superplastic microstructure of the base metal and so there has been much commercial interest in combining it with superplastic forming processes. Within this programme friction stir welding was performed with a variety of process parameters and in both the conventional and stationary shoulder configuration. This meant that a number of welds were created with various rates of heat input. The elevated temperature and intense plastic deformation associated with the friction stir welding process substantially alters the base metal microstructure. As a result the influence of the process parameters on the microstructure, texture and residual stress development has been identified within this investigation. Tool wear and deformation also remains a hindrance in the commercialisation of friction stir welding titanium alloys. Wear and deformation of the tool not only changes its shape, but it can have further implications on the structural integrity of the weld. Thus the influence of the process parameters on wear and deformation of the tool have also been identified.

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Duffey, Matthew James. "Metallurgical Characterization and Weldability Evaluation of Ferritic and Austenitic Welds in Armored Steels". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1460910681.

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Siggs, Eirian Bethany. "Laser and electron beam treatments for corrosion protection of friction stir welds in aerospace alloys". Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/479/.

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Friction Stir Welding (FSW) is a suitable technology for aerospace structure development and is a possible replacement for mechanical fastening. To achieve the application of FSW, pre and post-weld treatments are required. A pre-weld treatment of surface preparation was required to ensure a weld with good mechanical properties. The surface preparation necessary is the removal of paint and anodising layers from aerospace alloys. Laser paint removal was assessed and designed to remove these layers with only an oxide remaining, which welded to produce high quality welds. The post-weld treatment was essential to increase the corrosion resistance of the welded area. The improvement in corrosion resistance was achieved with High Power Beam Surface Modification (HPBSM), which created a homogeneous surface through rapid surface melting and solidification. The rapid thermal processing dissolved and dispersed the precipitate solute atoms which were retained in solid solution through planar solidification. Electron beams and various lasers were used in the HPBSM processing. Excimer Laser Surface Melting (LSM) improved corrosion resistance but the layer depth was restricted by processing parameters. HPBSM processing studies using an electron beam, USP-CO\(_2\) laser and Nd:YAG laser provided understanding on how processing parameters controlled the modified layer characteristics.

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Daus, Friedrich Herbert. "Process, microstructure and property relationships in dissimilar nickel base superalloy inertia friction welds". Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/1062/.

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The objective of this research was to study the difference in microstructure and high temperature fatigue behaviour between three RR1000 to IN718 inertia friction welds and to provide further understanding of the inertia friction welding process. Between the three welds no significant differences in the weld microstructures were found. Also high temperature fatigue crack growth tests within 0.3 mm of the weld interface, showed no difference in crack growth rate due to the three different sets of welding parameters. The cracks were found to propagate from RR1000 through the weld interface into IN718 passing a 10-30 mm wide zone, allowing higher crack growth rates. Fractographic studies have shown that these higher crack growth rates are caused by a higher tendency to intergranular cracking. In the present welds a semi-solid weld contact layer of 10 - 30 mm thickness developed, being an intermediate alloy of varying composition of the two base materials. In the surrounding material constitutional liquation of NbC particles in IN718 and of primary γ′ in RR1000 occurred. Similar welding process characteristics during the final second of the three welding cycles resulted in the observed similar weld microstructure and high temperature fatigue properties. It was further found that the local fatigue crack growth rate increase occurs in the weld contact layer.

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Khan, Fareed Ashraf. "Some aspects of convection as well as graphite and carbide formations during casting". Licentiate thesis, KTH, Metallernas gjutning, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-228388.

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It is an established fact that segregation during casting affects the physical properties of carbon-based ferro alloys; this motivates the study of the segregation behaviour of carbon and carbide-forming solute elements. In this context, this thesis investigates two different situations: the effects of cooling rate and turbulence on the precipitation behaviour of the graphite nodules in nodular cast iron; the nature of carbide precipitation in a bearing steel grade and the effects of subsequent soaking on these carbides. The structures of boiling water reactor inserts cast by the uphill and downhill casting of nodular cast iron were examined. The samples were taken from representative locations in the top, middle and bottom cross sections of the castings. It was observed that in uphill-cast inserts the nodules were larger but fewer in number the bottom section, whereas in downhill-cast inserts the nodules in the bottom section were smaller, but greater in number. Variation in volume fraction of the graphite nodules across the inserts was also observed. The probable cause of this variation was the difference in cooling rate in different sections of the insert. Between the steel tubes located at the central part of the casting, the fraction of graphite was lower, which could be the result of carburization of the steel tubes. To study the effects of melt stirring during the solidification of nodular cast iron, several experiments were conducted at variable cooling rates and for different stirring times. Examination of the microstructure was conducted using Light Optical Microscope (LOM) and Scanning Electron Microscope (SEM). It was observed that during stirring the melt oxidized and oxide nuclei were formed. The number of nucleation sites for the precipitation of graphite nodules increased, which raised the nodule count and the fraction of the graphite precipitated. The matrix transformed from pearlite to ferrite, which could be due to the fact that more carbon had diffused out of the matrix. The segregation behaviour in hypereutectoid bearing steel produced by ingot casting was also studied. The effects of soaking on micro and macro segregation was investigated in samples taken from as cast and soaked ingots; emphasis was laid on the bulk matrix and A-segregation channels. Samples were also taken from ingots which were soaked and then hot worked. The micro and macro examination of the microstructure was conducted using LOM and SEM. Quantitative and qualitative composition analysis was performed using Energy-dispersive X-ray spectroscopy (EDX) and an electron micro probe analyzer (EMPA). It was observed that M3C, M2C and M6C had precipitated. The carbide morphology in the bulk matrix was different to that in the A-segregation channels. All the primary carbides in the bulk matrix were found to have dissolved after 4 hours of soaking at 1200oC.
Det är ett faktum att segringar som uppstår under gjutning påverkar materialegenskaperna hos kolbaserade järnlegeringar; detta utgör motivationen till studien av segringsuppträdandet hos kol och karbidbildande ämnen. Denna avhandling behandlar två olika aspekter inom ramen för detta ämne: påverkan av kylningshastighet och turbulens på kärnbildningen av grafitnoduler i nodulärt gjutjärn samt karbidbildning i kullagerstål och dess påverkan på den efterföljande värmebehandlingen av dessa karbider. Strukturen hos rör till vattenkokare som tillverkats av nodulärt gjutjärn som gjutits med fyllning från botten eller från toppen undersöktes. Prover togs från representativa tvärsnittspositioner från toppen, mitten och botten av de gjutna ämnena. Resultaten visade att användandet av bottenfyllda kokiller gav upphov till större men färre karbider i nedre delen av ämnet, medans användandet av toppfyllda kokiller gav upphov till mindre men fler karbider i nedre delen av ämnet. Variationer av volymfraktionen av grafitnoduler längs tvärsnitten observerades också. Den mest sannolika orsaken till denna variation var skillnaden i kylhastighet i de olika områdena av tvärsnitten. Hos rör tillverkade av det centrala delen av ämnet så var fraktionen grafit lägre, vilket kan bero på en uppkolning av rören. Ett flertal experiment utfördes med varierande kylningshastigheter och olika omrörningstider för att studera inverkan av omrörning av smältan på stelningen av nodulärt gjutjärn. Studier av mikrostrukturen genomfördes med ljusoptisk mikroskopi och svepelektronmikroskopi. Resultaten visade att smältan oxiderades under omrörningen, vilket resulterade i bildandet av oxider. Detta ledde till en ökning av kärnbildningsområden för grafitnoduler, vilket ledde till en ökning av antalet noduler samt fraktionen av grafit som fälldes ut. Strukturen omvandlades från perlit till ferrit, vilket troligen orsakades av att kol hade diffunderat ut från strukturen. Segringsbeteendet hos hypereutektoida kullagerstål tillverkade genom götgjutning undersöktes också. Effekten av värmebehandling på mikro- och makrosegringar undersöktes i prover tagna från gjutna och värmebehandlade ämnen. Fokus var på att studera strukturen i ämnena samt A-segringar. Dessutom togs prover från ämnen som först värmebehandlats och därefter varmbearbetats. Både mikro- och makroundersökningar av mikrostrukturen utfördes med ljusoptisk mikroskopi och svepelektronmikroskopi. Dessutom så genomfördes kvantitativa sammansättningsbestämningar med energidispersiv röntgenspektroskopi och elektronmikroprobsanalys. Resultaten visade att M3C, M2C och M6C karbider hade fällts ut. Karbidmorfologin i huvuddelen av strukturen skiljde sig från den som återfanns i A-segringar. Samtliga primära karbider i huvuddelen av strukturen hade lösts upp efter 4 timmars värmebehandling vid 1200oC.

QC 20180523

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47

Peer, Andrea J. "Performance Testing and Modeling of Ultra-High Strength Steel and Complex Stack-Up Resistance Spot Welds". The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1493403670252986.

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48

Stritch, Kyle B. "Microstructural Evolution and Mechanical Properties in Simulated Heat Affected Zone Regions of Grade 91 Steel Welds". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471444438.

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Kusunoki, Takuya. "Quantification of the Tempering Response in Type 410 Steel Welds". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1607011624665895.

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SIVO, ANTONIO. "On the Laser Powder Bed Fusion based processing route for hard to weld Nickel Superalloys". Doctoral thesis, Politecnico di Torino, 2022. http://hdl.handle.net/11583/2971609.

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