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Author: Somayeh Pasebani
Publisher:
ISBN:
Category : Ferritic steel
Languages : en
Pages : 618
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Book Description
Oxide dispersion strengthened (ODS) alloys are potential candidates to be used as high temperature structural materials in advanced nuclear and fossil energy systems because of highly stable microstructure and high creep strength. The high temperature properties of these alloys are caused by high density of dislocations and grain boundaries that are effectively pinned by ultrafine Y-Ti-O-enriched particles. The traditional processing method of ODS alloys is via mechanical alloying (MA) of high chromium content powder in combination with up to 0.5 wt.% Y2O3, followed by hot consolidation via hot extrusion or hot isostatic pressing. In the current study, Fe-based ODS and nickel-based ODS alloys are developed by using spark plasma sintering (SPS). Furthermore, in Fe-based ODS alloys or so called nanostructured ferritic steels, Y2O3 is replaced by equal atomic percent of La2O3. Then, the effects of alloying composition, processing parameters including milling parameters and sintering parameters, on the microstructure characteristics and mechanical properties of the milled powder and consolidated alloys were investigated and structure-properties were correlated. Several Fe-14Cr based alloys with varying compositions were processed. Microstructural characteristics of the consolidated alloys were examined via transmission electron microscopy and atom probe tomography, and mechanical properties were evaluated using microhardness testing, shear punch testing and mini-compression testing. Lanthanum oxide (0.5 wt.%) was added to Fe-14Cr leading for improving microstructural stability and mechanical properties mainly due to a high number density of La-Cr-O-enriched nanoclusters (NCs). The combined addition of La, Ti (1 wt.%) and Mo (0.3 wt.%) to the Fe-14Cr base composition further enhanced the microstructural stability and mechanical properties. The NCs enriched in Cr-Ti-La-O with a number density of 1.4×1024 m−3 were found in this alloy (sintered at 950 °C for 7 min) with a bimodal grain size distribution. Formation mechanism of these NCs can be explained through the concentrations and diffusion rates of the initial oxide species formed during the milling process and initial stages of sintering as well as the thermodynamics nucleation barrier and their enthalpy of formation. Milling provided solid solution, high density of dislocations, vacancies in the powder and facilitated the nucleation of NCs and enhanced the densification behavior by initiating sintering at lower temperatures while lowering the activation energy for both grain boundary and volume diffusion. Significant densification occurred at temperatures greater than 950 °C with a relative density higher than 98%. High mechanical strength values were achieved in room and high temperature are due to the combined strengthening mechanisms of work hardening, grain refinement, dispersion strengthening and solid solution strengthening. The microstructure of lanthana-bearing NFS was stable after self-ion irradiation at 500 °C up to 100 dpa. A notable irradiation hardening and enhanced dislocation activity occurred after irradiation. On the other hand, nickel-based oxide dispersion strengthened (ODS) alloys were developed by adding 1.2 wt.% Y2O3 to Ni-20Cr matrix via MA and SPS. Additionally, 5 wt.% Al2O3 was added to Ni-20Cr-1.2Y2O3 to provide composite strengthening. Higher sintering temperature led to higher fraction of recrystallized grains, higher hardness, density, and higher volume fraction of annealing twins. Adding 1.2 wt.% Y2O3 to the Ni-20Cr matrix significantly reduced the grain size. Higher compression yield stress at 800 °C for Ni-20Cr-1.2Y2O3-5Al2O3 alloy was attributed to a combined effect of dispersion and composite strengthening.
Author: Somayeh Pasebani
Publisher:
ISBN:
Category : Ferritic steel
Languages : en
Pages : 618
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Book Description
Oxide dispersion strengthened (ODS) alloys are potential candidates to be used as high temperature structural materials in advanced nuclear and fossil energy systems because of highly stable microstructure and high creep strength. The high temperature properties of these alloys are caused by high density of dislocations and grain boundaries that are effectively pinned by ultrafine Y-Ti-O-enriched particles. The traditional processing method of ODS alloys is via mechanical alloying (MA) of high chromium content powder in combination with up to 0.5 wt.% Y2O3, followed by hot consolidation via hot extrusion or hot isostatic pressing. In the current study, Fe-based ODS and nickel-based ODS alloys are developed by using spark plasma sintering (SPS). Furthermore, in Fe-based ODS alloys or so called nanostructured ferritic steels, Y2O3 is replaced by equal atomic percent of La2O3. Then, the effects of alloying composition, processing parameters including milling parameters and sintering parameters, on the microstructure characteristics and mechanical properties of the milled powder and consolidated alloys were investigated and structure-properties were correlated. Several Fe-14Cr based alloys with varying compositions were processed. Microstructural characteristics of the consolidated alloys were examined via transmission electron microscopy and atom probe tomography, and mechanical properties were evaluated using microhardness testing, shear punch testing and mini-compression testing. Lanthanum oxide (0.5 wt.%) was added to Fe-14Cr leading for improving microstructural stability and mechanical properties mainly due to a high number density of La-Cr-O-enriched nanoclusters (NCs). The combined addition of La, Ti (1 wt.%) and Mo (0.3 wt.%) to the Fe-14Cr base composition further enhanced the microstructural stability and mechanical properties. The NCs enriched in Cr-Ti-La-O with a number density of 1.4×1024 m−3 were found in this alloy (sintered at 950 °C for 7 min) with a bimodal grain size distribution. Formation mechanism of these NCs can be explained through the concentrations and diffusion rates of the initial oxide species formed during the milling process and initial stages of sintering as well as the thermodynamics nucleation barrier and their enthalpy of formation. Milling provided solid solution, high density of dislocations, vacancies in the powder and facilitated the nucleation of NCs and enhanced the densification behavior by initiating sintering at lower temperatures while lowering the activation energy for both grain boundary and volume diffusion. Significant densification occurred at temperatures greater than 950 °C with a relative density higher than 98%. High mechanical strength values were achieved in room and high temperature are due to the combined strengthening mechanisms of work hardening, grain refinement, dispersion strengthening and solid solution strengthening. The microstructure of lanthana-bearing NFS was stable after self-ion irradiation at 500 °C up to 100 dpa. A notable irradiation hardening and enhanced dislocation activity occurred after irradiation. On the other hand, nickel-based oxide dispersion strengthened (ODS) alloys were developed by adding 1.2 wt.% Y2O3 to Ni-20Cr matrix via MA and SPS. Additionally, 5 wt.% Al2O3 was added to Ni-20Cr-1.2Y2O3 to provide composite strengthening. Higher sintering temperature led to higher fraction of recrystallized grains, higher hardness, density, and higher volume fraction of annealing twins. Adding 1.2 wt.% Y2O3 to the Ni-20Cr matrix significantly reduced the grain size. Higher compression yield stress at 800 °C for Ni-20Cr-1.2Y2O3-5Al2O3 alloy was attributed to a combined effect of dispersion and composite strengthening.
Author: Anshuman Patra
Publisher: CRC Press
ISBN: 1000580555
Category : Technology & Engineering
Languages : en
Pages : 199
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Book Description
Refractory metals such as W, Mo, Ta, Nb, and Re have immense potential for application in plasma-facing materials in nuclear reactors, defense materials, aviation counterweights, heating elements in furnaces, and so forth. This book presents a wide perspective of oxide dispersion strengthened refractory alloys fabrication and critical properties. It provides a comprehensive road map for an appropriate basis for alloy design, process parameter selection, fabrication route, and deformation behavior for oxide dispersion strengthened refractory alloys. It further covers achievement of application-oriented properties and critical process-regulating parameters for development of sustainable materials. Features: Covers development of oxide dispersion strengthened sustainable material to withstand high-temperature environments Describes stimulating application-oriented final mechanical properties Illustrates fabrication of alloys through effective route to achieve desired properties Presents in-depth explanation of deformation behavior at ambient and high temperatures Explores critical applications of the alloys in nuclear reactors, defense, and aviation sectors Oxide Dispersion Strengthened Refractory Alloys will be of interest to graduate students and researchers in high-temperature materials, mechanics, metallurgy, powder metallurgy, and physical metallurgy.
Author: Arnab Kundu
Publisher:
ISBN: 9781085578196
Category : Chromium-iron alloys
Languages : en
Pages : 360
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Book Description
Fe-Cr based oxide dispersion strengthened (ODS) alloys are potential candidates for usage as nuclear fuel cladding material for the upcoming Generation-IV nuclear reactor, especially in liquid sodium cooled fast reactors. These high performance materials have many advantages since they possess remarkable mechanical strength at high temperature and outstanding irradiation resistance. Particularly, ODS steels known as nanostructured ferritic alloys have negligible swelling under irradiation, and equally excellent creep properties because of nano-reinforcements i.e. the nanometric oxides present in the matrix. Traditionally, ODS processing combines mechanical alloying (MA) followed by hot consolidation via hot extrusion and hot isostatic pressing. In the present study, the ODS alloys are produced by a combined route of MA and Spark Plasma Sintering (SPS). After consolidation, the effects of processing parameters including milling parameters and sintering parameters, on the microstructure characteristics and mechanical properties of the milled powder and consolidated alloys are investigated. Once the suitable parameters are decided for the maximum compaction state for Fe-9Cr alloy, Fe-Cr alloys were produced with varying Cr content to understand the effect of Cr on the process of MA and SPS. Secondly, the effect of bimodal distribution obtained by various MA time has been observed after consolidation process. Finally, having understood the basic fundamentals of processing of Fe-Cr alloys, Fe-9Cr ODS was produced with addition of W and Ti and oxide particles as dispersoid phase. During the process of MA, the oxides get dissolved in the matrix and during consolidation process these oxides get precipitated as nanophases in the matrix thus resulting in the higher strength. In general, yttria (Y2O3) has been used as the oxide which is added to the Fe-Cr alloy system. Recently some work has been done on the addition of lanthana (La2O3). In this study, we have introduced a new oxide (CeO2) in the same amount (wt%) compared to Y2O3 and La2O3 to understand the effect of CeO2 on the ODS alloy. Powder and consolidated alloys characterization were performed using Scanning electron microscopy (SEM), Electron backscatter diffraction (EBSD) and Transmission electron microscopy (TEM). The mechanical properties were evaluated using microhardness testing and mini-compression testing. Corrosion tests were conducted at room temperature in various to understand the nature of the oxide layer formed on the Fe-Cr and Fe-9Cr ODS materials. Mechanical alloying created high density of dislocations, vacancies in the powder and facilitated the nucleation of NCs. It resulted in faster densification behavior by initiating sintering at lower temperatures by lowering the activation energy for both grain boundary and volume diffusion. Maximum densification (around 98%) occurred at temperatures 1000 °C for a sintering time of 45 min at 80 MPa pressure for 10 h ball milled powder. Due to the combined strengthening mechanisms of work hardening, grain refinement, dispersion strengthening and solid solution strengthening, superior strength was achieved for the materials. On addition of alloying elements and the rare earth oxides, the presence of second phase particles like Cr0.875Ti0.125 is observed along with Ti-Cr-O-RE type precipitates which imparts high strength to the matrix both at room temperature an at elevated temperatures.
Author: Pasquale Cavaliere
Publisher: Springer
ISBN: 303005327X
Category : Technology & Engineering
Languages : en
Pages : 781
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Book Description
This book describes spark plasma sintering (SPS) in depth. It addresses fundamentals and material-specific considerations, techniques, and applications across a broad spectrum of materials. The book highlights methods used to consolidate metallic or ceramic particles in very short times. It highlights the production of complex alloys and metal matrix composites with enhanced mechanical and wear properties. Emphasis is placed on the speed of the sintering processes, uniformity in product microstructure and properties, reduced grain growth, the compaction and sintering of materials in one processing step, various materials processing, and high energy efficiency. Current and potential applications in space science and aeronautics, automation, mechanical engineering, and biomedicine are addressed throughout the book.
Author: Cury Suryanarayana
Publisher: CRC Press
ISBN: 0203020642
Category : Technology & Engineering
Languages : en
Pages : 488
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Book Description
This book surveys the broad field of mechanical alloying from a scientific and technological perspective to form a timely and comprehensive resource valuable to both students and researchers. The treatment progresses from the historical background through a description of the process, the different metastable effects produced, and the mechanisms of
Author: Małgorzata Sopicka-Lizer
Publisher: Elsevier
ISBN: 1845699440
Category : Technology & Engineering
Languages : en
Pages : 436
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Book Description
Mechanochemical processing is a novel and cost effective method of producing a wide range of nanopowders. It involves the use of a high energy ball mill to initiate chemical reactions and structural changes. High energy ball milling: Mechanochemical processing of nanopowders reviews the latest techniques in mechanochemistry and how they can be applied to the synthesis and processing of various high-tech materials.Part one discusses the basic science of mechanochemistry with chapters on such topics as the mechanism and kinetics of mechanochemical processes, kinetic behaviour in mechanochemically-induced structural and chemical transformations and materials design through mechanochemical processing. Part two reviews mechanochemical treatment of different materials including synthesis of complex ceramic oxides, production of intermetallic compound powders, synthesis of organic compounds, synthesis of metallic-ceramic composite powders and activation of covalent bond-based materials. Part three covers mechanochemical processes in metal powder systems and other applications with coverage of topics such as plating and surface modification using ultrasonic vibrations, activated powders as precursors for spark plasma sintering, titanium dioxide photocatalyst synthesis by mechanochemical doping and synthesis of materials for lithium-ion batteries.With its distinguished editor and international team of contributors, High energy ball milling: Mechanochemical processing of nanopowders is a standard reference for all those involved in the production of ceramic and metallic components using sintering and other powder metallurgy techniques to produce net shape components. - Examines the latest techniques in mechanochemistry and how they can be applied to the synthesis and processing of various high-tech materials - Discusses the basic science of mechanochemistry including kinetic behaviour, processes and mechanisms and materials design through mechanochemical processing - Reviews mechanochemical treatment of different materials including synthesis of ceramic oxides, organic compounds and metallic-ceramic composite powders
Author: Isaac Chang
Publisher: Elsevier
ISBN: 085709890X
Category : Technology & Engineering
Languages : en
Pages : 624
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Book Description
Powder metallurgy (PM) is a popular metal forming technology used to produce dense and precision components. Different powder and component forming routes can be used to create an end product with specific properties for a particular application or industry. Advances in powder metallurgy explores a range of materials and techniques used for powder metallurgy and the use of this technology across a variety of application areas. Part one discusses the forming and shaping of metal powders and includes chapters on atomisation techniques, electrolysis and plasma synthesis of metallic nanopowders. Part two goes on to highlight specific materials and their properties including advanced powdered steel alloys, porous metals and titanium alloys. Part three reviews the manufacture and densification of PM components and explores joining techniques, process optimisation in powder component manufacturing and non-destructive evaluation of PM parts. Finally, part four focusses on the applications of PM in the automotive industry and the use of PM in the production of cutting tools and biomaterials. Advances in powder metallurgy is a standard reference for structural engineers and component manufacturers in the metal forming industry, professionals working in industries that use PM components and academics with a research interest in the field. Discusses the forming and shaping of metal powders and includes chapters on atomisation techniques Highlights specific materials and their properties including advanced powdered steel alloys, porous metals and titanium alloys Reviews the manufacture and densification of PM components and explores joining techniques
Author: Joan-Josep Suñol
Publisher: Mdpi AG
ISBN: 9783036521176
Category : Technology & Engineering
Languages : en
Pages : 134
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Book Description
Mechanical alloying is a technique of producing alloys and compounds that permits the development of metastable materials (with amorphous or nanocrystalline microstructure) or the fabrication of solid solutions with extended solubility. The elements or compounds to be mixed (usually as powders) are introduced in jars usually under a controlled atmosphere. Regarding the scope of this book, advanced materials have been developed by mechanical alloying: Fe-X-B-Cu (X = Nb, NiZr) nanocrystalline alloys, mixtures of the binary Fe-Mn and Fe-Cr alloys with chromium and manganese nitrides, Mn-Al-Co and Mn-Fe alloys, non-equiatomic refractory high-entropy alloys, nanocrystalline Fe-Cr steels, nanaocrystalline Mn-Co-Fe-Ge-Si alloys, Al-Y2O3 nanocomposite, and hydride-forming alloys. Likewise, production conditions and ulterior treatments can provide readers interesting ideas about the procedure to produce alloys with specific microstructure and functional behavior (mechanical, magnetic, corrosion resistance, hydrogen storage, magnetocaloric effect, wastewater treatment, and so on). As an example, to obtain the improvement in the functional properties of the alloys and compounds, sometimes controlled annealing is needed (annealing provokes the relaxation of the mechanical-induced strain). Furthermore, the powders can be consolidated (press, spark plasma sintering, and microwave sintering) to obtain bulk materials.
Author: Eugene A. Olevsky
Publisher: Springer
ISBN: 3319760327
Category : Technology & Engineering
Languages : en
Pages : 432
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Book Description
This book represents the first ever scientific monograph including an in-depth analysis of all major field-assisted sintering techniques. Until now, the electromagnetic field-assisted technologies of materials processing were lacking a systematic and generalized description in one fundamental publication; this work promotes the development of generalized concepts and of comparative analyses in this emerging area of materials fabrication. This book describes modern technologies for the powder processing-based fabrication of advanced materials. New approaches for the development of well-tailored and stable structures are thoroughly discussed. Since the potential of traditional thermo-mechanical methods of material treatment is limited due to inadequate control during processing, the book addresses ways to more accurately control the resultant material's structure and properties by an assisting application of electro-magnetic fields. The book describes resistance sintering, high-voltage consolidation, sintering by low-voltage electric pulses (including spark plasma sintering), flash sintering, microwave sintering, induction heating sintering, magnetic pulse compaction and other field-assisted sintering techniques. Includes an in-depth analysis of all major field-assisted sintering techniques; Explains new techniques and approaches for material treatment; Provides detailed descriptions of spark plasma sintering, microwave sintering, high-voltage consolidation, magnetic pulse compaction, and various other approaches when field-assisted treatment is applied.
Author: YONG-DEOG. KIM
Publisher:
ISBN:
Category :
Languages : en
Pages : 224
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Book Description
The intermetallic compound, B2 NiAl, is a promising material for high temperature structural applications such as in aviation jet engines or gas turbines, provided that its high temperature mechanical properties can be improved. Although extensive efforts over the last several decades have been devoted toward enhancing ductility through alloying design and reducing impurities, as well as improving high temperature creep strength through precipitation and dispersion strengthening, these efforts have relied on traditional approaches, a combination of large grain size to limit diffusional creep and precipitation/dispersion (50 ~ 100 nm size) strengthening to limit dislocation creep, for high temperature strengthening. While traditional approaches have shown a good improvement from a relatively high temperature strengthening point of view, the size and number density of dispersoids were not able to provide sufficient strength in the high temperature creep regime. Furthermore, details of the interaction mechanism between dislocations and dispersoids are not yet well understood. This study focuses on designing and developing advanced oxide dispersion strengthened (ODS) NiAl intermetallics with improved high temperature creep strength by incorporating a high number density (~1024 m-3) of very thermally stable Y-Ti-O nano-clusters, akin to those recently observed to improve creep strength and radiation resistance in nano-structured ferritic alloys. Advanced ODS NiAl alloys have been produced by mechanical alloying of pre-alloyed Ni-50at%Al with Y2O3 and Ti elemental powders. The milled powders were subsequently consolidated by spark plasma sintering, with the objective of producing very high number densities of nano-sized Y-Ti-O precipitates, along with fine grain size. Advanced experimental characterization techniques, combined with microhardness strength measurement, were used to investigate the material microstructure and strength following processing and to evaluate the thermal stability during an extensive matrix of long-term thermal annealing. In particular, the size, number density and composition of nano-clusters were assessed. While improvements in strength were obtained in the advanced NiAl ODS alloys, and the higher strength persisted through thermal annealing for 100 hrs at 1723K, characterization revealed the presence of Al in the oxide precipitate phases. The Al incorporation is believed detrimental to the formation of a high density of thermally stable Y-Ti-O nanoscale precipitates.
