A Study of Microstructure Evolution and Its Effect on the Mechanical Anisotropic Behavior of an Al-Mg-Si Alloy PDF Download
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Author: Zhong Li
Publisher:
ISBN:
Category :
Languages : en
Pages : 410
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Author: Zhong Li
Publisher:
ISBN:
Category :
Languages : en
Pages : 410
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Author: Cheng-Han Yu
Publisher: Linköping University Electronic Press
ISBN: 9179298117
Category :
Languages : en
Pages : 51
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Additive manufacturing (AM), also known as 3D printing, is a concept and method of a manufacturing process that builds a three-dimensional object layer-by-layer. Opposite to the conventional subtractive manufacturing, it conquers various limitations on component design freedom and raises interest in various fields, including aerospace, automotive and medical applications. This thesis studies the mechanical behavior of thin-walled component manufactured by a common AM technique, laser powder bed fusion (LPBF). The studied material is Hastelloy X, which is a Ni-based superalloy, and it is in connection to a component repair application in gas turbines. The influence of microstructure on the deformation mechanisms at elevated temperatures is systematically investigated. This study aims for a fundamental and universal study that can apply to different material grades with FCC crystallographic structure. It is common to find elongated grain and subgrain structure caused by the directional laser energy input in the LPBF process, which is related to the different printing parameters and brands of equipment. This thesis will start with the study of scan rotation effect on stainless steel 316L in an EOS M290 equipment. The statistic texture analysis by using neutron diffraction reveals a clear transition when different level of scan rotation is applied. Scan rotation of 67° is a standard printing parameter with intention to lower anisotropy, yet, the elongated grain and cell structure is still found in the as-built microstructure. Therefore, the anisotropic mechanical behavior study is carried out on the sample printed with scan rotation of 67° in this thesis. Thin-walled effects in LPBF are investigated by studying a group of plate-like HX specimens, with different nominal thicknesses from 4mm down to 1mm, and a reference group of rod-like sample with a diameter of 18mm. A texture similar to Goss texture is found in rod-like sample, and it becomes <011>//BD fiber texture in the 4mm specimen, then it turns to be <001> fiber texture along the transverse direction (TD) in the 1mm specimen. Tensile tests with the strain rate of 10?3 s?1 have been applied to the plate-like specimens from room temperature up to 700 ?. A degradation of strength is shown when the sample becomes thinner, which is assumed to be due to the overestimated load bearing cross-section since the as-built surface is rough. A cross-section calibration method is proposed by reducing the surface roughness, and a selection of proper roughness parameters is demonstrated with the consideration of the calculated Taylor’s factor and the residual stress. The large thermal gradient during the LPBF process induces high dislocation density and strengthens the material, hence, the LPBF HX exhibits better yield strength than conventionally manufactured, wrought HX, but the work hardening capacity and ductility are sacrificed at the same time. Two types of loading condition reveal the anisotropic mechanical behavior, where the vertical and horizontal tests refer to the loading direction being on the BD and TD respectively. The vertical tests exhibit lower strength but better ductility that is related to the larger lattice rotation observed from the samples with different deformation level. Meanwhile, the elongated grain structure and grain boundary embrittlement are responsible for the low horizontal ductility. A ductile to brittle transition is traced at 700 ?, so a further study with two different slow strain rates, 10?5 s?1 and 10?6 s?1, are carried out at 700 ?. Creep damage is shown in the slow strain rates testing. Deformation twinning is found only in the vertical tests where it forms mostly in the twin favorable <111> oriented grain along the LD. The large lattice rotation and the deformation twinning make the vertical ductility remain high level under the slow strain rates. The slow strain rate tensile testing lightens the understanding of creep behavior in LPBF Ni-based superalloys. In summary, this thesis uncovers the tensile behavior of LPBF HX with different variations, including geometry-dependence, temperature-dependence, crystallographic texture-dependence and strain rate-dependence. The generated knowledge will be beneficial to the future study of different mechanical behavior such as fatigue and creep, and it will also enable a more robust design for LPBF applications. Additiv tillverkning, eller 3D-utskrifter, är tillverkningsmetoder där man skapar ett tredimensionellt objekt genom att tillföra material lager for lager. Till skillnad från konventionella avverkande tillverkningsmetoder elimineras många geometriska begränsningar vilket ger större designfrihet och metoderna har därför väckt stort intresse inom en rad olika områden, inklusive flyg-, fordons- och medicinska tillämpningar. I denna avhandling studeras mekaniska egenskaper hos tunnväggiga komponenter tillverkade med en vanligt förekommande laserbaserad pulverbädds-teknik, laser powder bed fusion (LPBF). Det studerade materialet är Hastelloy X, en Ni-baserad superlegering som är vanligt förekommande for både nytillverkning och reparation av komponenter för gasturbiner. Inverkan av mikrostruktur på deformationsmekanismerna vid förhöjda temperaturer undersöks systematiskt. Detta arbete syftar till att ge grundläggande och generisk kunskap som kan tillämpas på olika materialtyper med en kubiskt tätpackad (FCC) kristallstruktur. Det är vanligt att man hittar en utdragen kornstruktur orsakad av den riktade tillförseln av laserenergi i LPBF-processen, vilket kan relateras till olika processparametrar och kan variera mellan utrustningar frän olika leverantörer. Denna avhandling inleds med studien av effekten av scanningsstrategi vid tillverkning av rostfritt stål 316L i en EOS M290-utrustning. En statistisk texturanalys med hjälp av neutrondiffraktion påvisar en tydlig övergång mellan olika mikrostrukturer när olika scanningsstrategier tillämpas. En scanningsrotation på 67 mellan varje lager är en typisk standardinställning med avsikt att sanka anisotropin i materialet, dock finns den utdragna kornstrukturen oftast kvar. I denna avhandling studeras därför de anisotropa egenskaperna hos material tillverkade med 67 scanningsrotation. Effekten av tunnväggiga strukturer i LPBF undersöks genom att studera en uppsättning platta HX-prover, med olika nominella tjocklekar från 4 mm ner till 1 mm, samt en referensgrupp med cylindriska prov med en diameter på 18 mm. Kristallografisk textur som liknar den av Goss-typ återfinns i de cylindriska proverna vilket gradvis övergår från en fibertextur med <011> i byggriktningen for 4mm-proven till en fibertextur med <001> i tvärriktningen for 1mm-proven. Dragprovning med en töjningshastighet på 10?3 s?1 har utförts på de platta provstavarna från rumstemperatur upp till 700 ?. En sänkning av styrkan uppvisas när proven blir tunnare, vilket kan antas bero på att det lastbarande tvärsnittet överskattas på grund av den grova ytan. En metod för tvärsnittskalibrering föreslås genom att kompensera for ytråheten, och valet av lämplig ytfinhetsparameter motiveras med hänsyn till den beräknade Taylor-faktorn och förekomsten av restspänningar. Den stora termiska gradienten som uppstår for LPBF-processen inducerar en hög dislokationstäthet vilket höjer materialets styrka och följaktligen uppvisar LPBF HX högre sträckgräns an konventionellt tillverkad, smidda HX, men förmågan till deformationshårdnande samt duktiliteten i materialet sänks samtidigt. Tester utförda i två olika belastningsriktningar, vertikalt respektive horisontellt mot byggriktningen, demonstrerar det anisotropiska mekaniska beteendet. De vertikala testerna uppvisar lägre hållfasthet men bättre duktilitet vilket kan relateras till en större benägenhet for kristallstukturen att rotera när deformationsgraden ökar. Samtidigt är den utdragna kronstukturen ansvarig for den lägre duktiliteten for de horisontella proverna. En övergång från ett duktilt till ett mer sprött beteende noterades vid 700 ?, och därför initierades ytterligare en studie där tester med två lägre töjningshastigheter, 10?5 s?1 och 10?6 s?1, utfördes vid 700 ?. Det kan noteras att krypskador återfinns i tester med en långsam deformationshastighet och deformationstvillingar uppstår endast i de vertikala provstavarna där det främst bildas tvillingar i korn orienterade med <111> riktningen längs belastningsriktningen. Den stora förmågan till rotation i kristallstrukturen och deformationstvillingarna bidrar till att den vertikala duktiliteten förblir hög även i testerna med en låg deformationshastighet. Testerna med en långsam draghastighet bidrar därför till en bättre förståelse av krypbeteendet i LPBF Nibaserade superlegeringar. Sammanfattningsvis så bidrar denna avhandling till bättre förståelse av de mekaniska egenskaperna hos LPBF HX i olika utföranden och förhållanden, inklusive geometriberoende, temperaturberoende, deformationshastighetsberoende samt inverkan av kristallografisk textur. Den genererade kunskapen kommer att vara till stor nytta vid fortsatta studier av olika mekaniska egenskaper som utmattning och kryp, samt bidrar till att möjliggöra en mer robust design for LPBF-tillämpningar.
Author:
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ISBN:
Category : Dissertation abstracts
Languages : en
Pages : 806
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Author: Baolute Ren
Publisher:
ISBN:
Category :
Languages : en
Pages : 472
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Author: Konstantin Naumenko
Publisher: Springer
ISBN: 331931629X
Category : Science
Languages : en
Pages : 381
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This monograph presents approaches to characterize inelastic behavior of materials and structures at high temperature. Starting from experimental observations, it discusses basic features of inelastic phenomena including creep, plasticity, relaxation, low cycle and thermal fatigue. The authors formulate constitutive equations to describe the inelastic response for the given states of stress and microstructure. They introduce evolution equations to capture hardening, recovery, softening, ageing and damage processes. Principles of continuum mechanics and thermodynamics are presented to provide a framework for the modeling materials behavior with the aim of structural analysis of high-temperature engineering components.
Author: Francis H. Froes
Publisher: Elsevier
ISBN: 0128140631
Category : Technology & Engineering
Languages : en
Pages : 483
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Additive Manufacturing for the Aerospace Industry explores the design, processing, metallurgy and applications of additive manufacturing (AM) within the aerospace industry. The book's editors have assembled an international team of experts who discuss recent developments and the future prospects of additive manufacturing. The work includes a review of the advantages of AM over conventionally subtractive fabrication, including cost considerations. Microstructures and mechanical properties are also presented, along with examples of components fabricated by AM. Readers will find information on a broad range of materials and processes used in additive manufacturing. It is ideal reading for those in academia, government labs, component fabricators, and research institutes, but will also appeal to all sectors of the aerospace industry. - Provides information on a broad range of materials and processes used in additive manufacturing - Presents recent developments in the design and applications of additive manufacturing specific to the aerospace industry - Covers a wide array of materials for use in the additive manufacturing of aerospace parts - Discusses current standards in the area of aerospace AM parts
Author: Stephan Broek
Publisher: Springer Nature
ISBN: 3031225325
Category : Technology & Engineering
Languages : en
Pages : 1336
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The Light Metals symposia at the TMS Annual Meeting & Exhibition present the most recent developments, discoveries, and practices in primary aluminum science and technology. The annual Light Metals volume has become the definitive reference in the field of aluminum production and related light metal technologies. The 2023 collection includes contributions from the following symposia: · 60 Years of Taking Aluminum Smelting Research and Development from New Zealand to the World: An LMD Symposium in Honor of Barry J. Welch · Alumina & Bauxite · Aluminium Industry Emissions Measurement, Reporting & Reduction · Aluminium Waste Management & Utilisation · Aluminum Alloys, Characterization and Processing · Aluminum Reduction Technology · Cast Shop Technology · Electrode Technology for Aluminum Production · Scandium Extraction and Use in Aluminum Alloys
Author: Hasse Fredriksson
Publisher: John Wiley & Sons
ISBN: 1119978327
Category : Technology & Engineering
Languages : en
Pages : 837
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Solidification and Crystallization Processing in Metals and Alloys Hasse Fredriksson KTH, Royal Institute of Technology, Stockholm, Sweden Ulla Åkerlind University of Stockholm, Sweden Solidification or crystallization occurs when atoms are transformed from the disordered liquid state to the more ordered solid state, and is fundamental to metals processing. Conceived as a companion volume to the earlier works, Materials Processing during Casting (2006) and Physics of Functional Materials (2008), this book analyzes solidification and crystallization processes in depth. Starting from the thermodynamic point of view, it gives a complete description, taking into account kinetics and mass transfer, down to the final structure. Importantly, the book shows the relationship between the theory and the experimental results. Topics covered include: Fundamentals of thermodynamics Properties of interfaces Nucleation Crystal growth - in vapours, liquids and melts Heat transport during solidification processes Solidification structures - faceted, dendritic, eutectic and peritectic Metallic glasses and amorphous alloy melts Solidification and Crystallization Processing in Metals and Alloys features many solved examples in the text, and exercises (with answers) for students. Intended for Masters and PhD students as well as researchers in Materials Science, Engineering, Chemistry and Metallurgy, it is also a valuable resource for engineers in industry.
Author: Zhenzhen Yu
Publisher:
ISBN:
Category :
Languages : en
Pages : 148
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In this thesis, the relationship among friction stir processing (FSP) parameters, microstructure evolution, texture development, and mechanical hehavior[sic] of AZ31B Mg alloy was investigated. First of all, in order to reveal the correlation among the deformation conditions, dynamic recrystallization (DRX) mechanisms, and microstructure evolution in the Mg alloy, hot compression tests at a wide range of Zener-Hollomon parameter (Z) values were conducted. Through optical microscopic examination, it was found out that above a critical Z value, twinning influences the DRX process resulting in a more effective grain refinement, which is manifested in a significant change in the slope of the Z-d[subscript rec] relationship, where d[subscript rec] is the recrystallized grain size. Moreover, EBSD examination revealed that the twinning also contributed to a distinct change in the recrystallization texture. Compression tests were performed along both through-thickness and in-rolling-plane directions of the plate to study the orientation dependency of twinning activities and its influence on the DRX process. X-ray line profile analysis (XLPA) provides further insights by highlighting the differences in the dislocation density/types, subgrain sizes, and twin densities during the DRX processes operating with or without the twinning. Secondly, the constitutive behaviour study was applied to the investigation of microstructure evolution during FSP. By varying the key FSP parameters systematically, i.e. rotation and travel rates of the tool, a series of FSP specimens were prepared with a wide range of thermo-mechanical inputs in terms of Z. The resulting tensile behavior in the stir zone (SZ) showed a dramatic change as a function of Z, caused by a systematic change in the texture within SZ measured by neutron diffraction. A three-dimensional transient model was developed to investigate the detailed deformation history including the temperature and strain rate profiles and material flow pattern during FSP of the Mg alloy. Such deformation history can be combined with the constitutive study from the compression tests in order to analyze the developments of micro-texture and DRX grains during FSP, which will, in turn, dominate the mechanical properties. Based on the studies above, new fundamental understandings were gained on the governing mechanisms for the deformation and recrystallization processes during FSP and the influence of thermo-mechanical input during FSP on ductility enhancement in the Mg alloy.
Author: The Minerals, Metals & Materials Society (TMS)
Publisher: John Wiley & Sons
ISBN: 1119274877
Category : Technology & Engineering
Languages : en
Pages : 886
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Book Description
The TMS 2016 Annual Meeting Supplemental Proceedings is a collection of papers from the TMS 2016 Annual Meeting & Exhibition, held February 14-18 in Nashville, Tennessee, USA. The papers in this volume represent 21 symposia from the meeting. This volume, along with the other proceedings volumes published for the meeting, and archival journals, such as Metallurgical and Materials Transactions and Journal of Electronic Materials, represents the available written record of the 67 symposia held at TMS2016. This proceedings volume contains both edited and unedited papers; the unedited papers have not necessarily been reviewed by the symposium organizers and are presented “as is.” The opinions and statements expressed within the papers are those of the individual authors only, and no confirmations or endorsements are intended or implied.
