Recursos de colección

ETD at Indian Institute of Science (2.878 recursos)

Repository of Theses and Dissertations of Indian Institute of Science, Bangalore, India. The repository has been developed to capture, disseminate and preserve research theses of Indian Institute of Science.

Metallurgy (metalrg)

Mostrando recursos 1 - 20 de 106

  1. Fracture and Deformation in Bulk Metallic Glasses and Composites

    Narayan, R Lakshmi
    Plastic flow in bulk metallic glasses (BMGs) localizes into narrow bands, which, in the absence of a microstructure that could obstruct them, propagate unhindered under tensile loading. In constrained deformation conditions such as indentation and at notch roots, extensive shear band formation can occur. A key issue in the context of fracture of BMGs that is yet to be understood comprehensively is how their toughness is controlled by various state parameters. Towards this end, the change in fracture toughness and plasticity with short term annealing above and below the glass transition temperature, Tg, is studied in a Zr-based BMG. Elastic...

  2. Microstructural, Mechanical and Oxidation Behavior of Ni-Al-Zr Ternary Alloys

    Tiwary, Chandra Sekhar
    The thesis introduces a novel alloy system based on submicron distributions of intermetallic phases realised through eutectic solidification in the ternary system Ni-Al-Zr. Various compositions in this system comprising of intermetallic phases distributed in different eutectic structures show ultra-high strength at temperatures upto 700°C combined with reasonable tensile plasticity, exceptional oxidation resistance and high temperature structural stability. Intermetallics have long been used in high temperature alloys systems such as in the classical Ni-base superalloys that derive their strength from nanoscale dispersions of the aluminide, Ni3Al(γ’) in a matrix of disordered fcc Ni (γ), alloyed with expensive, high density refractory elements...

  3. Microstructural, Mechanical and Oxidation Behavior of Ni-Al-Zr Intermetallic Eutectic Alloys

    Gunjal, Vilas Vishnu
    The excellent high temperature microstructure stability, high strength, and oxidation resistance of intermetallics has for long driven the development of intermetallic based alloys. More recent studies demonstrated attractive properties of eutectic intermetallic in the Ni-Al-Zr systems. This thesis deals with study of binary Ni3Al+Ni7Zr2, NiAl+Ni7Zr2 and Ni3Al+NiAl+Ni7Zr2 ternary intermetallic eutectic alloys in this system and includes the identification of compositions that would yield each eutectic structure and their microstructural characterization, mechanical and oxidation behavior. The thesis is divided into six chapters. Chapter 1 reviews the study on high temperature materials development and presents the objectives of work in the current...

  4. Microstructural, Mechanical and Oxidation Behavior of Ni-Al-Zr Intermetallic Eutectic Alloys

    Gunjal, Vilas Vishnu
    The excellent high temperature microstructure stability, high strength, and oxidation resistance of intermetallics has for long driven the development of intermetallic based alloys. More recent studies demonstrated attractive properties of eutectic intermetallic in the Ni-Al-Zr systems. This thesis deals with study of binary Ni3Al+Ni7Zr2, NiAl+Ni7Zr2 and Ni3Al+NiAl+Ni7Zr2 ternary intermetallic eutectic alloys in this system and includes the identification of compositions that would yield each eutectic structure and their microstructural characterization, mechanical and oxidation behavior. The thesis is divided into six chapters. Chapter 1 reviews the study on high temperature materials development and presents the objectives of work in the current...

  5. Evolution of Microstructure and Texture during Severe Plastic Deformation of a Magnesium-Cerium Alloy

    Sabat, Rama Krushna
    Magnesium alloys have poor formability at room temperature, due to a limited number of slip systems owing to the hexagonal closed packed structure of magnesium. One possibility to increase the formability of magnesium alloys is to refine the grain size. A fine grain magnesium alloy shows high strength and high ductility at room temperature, hence an improved formability. In addition to grain refinement, the formability of Mg alloys can be improved by controlling crystallographic texture. Severe plastic deformation (SPD) processes namely, equal channel angular pressing (ECAP) and multi-axial forging (MAF) have led to improvement in room temperature mechanical property of...

  6. Evolution of Microstructure and Texture during Severe Plastic Deformation of a Magnesium-Cerium Alloy

    Sabat, Rama Krushna
    Magnesium alloys have poor formability at room temperature, due to a limited number of slip systems owing to the hexagonal closed packed structure of magnesium. One possibility to increase the formability of magnesium alloys is to refine the grain size. A fine grain magnesium alloy shows high strength and high ductility at room temperature, hence an improved formability. In addition to grain refinement, the formability of Mg alloys can be improved by controlling crystallographic texture. Severe plastic deformation (SPD) processes namely, equal channel angular pressing (ECAP) and multi-axial forging (MAF) have led to improvement in room temperature mechanical property of...

  7. Experimental and Numerical Investigation on Friction Welding of Thixocast A356 Aluminium Alloy

    Singh, Shailesh Kumar
    The challenges of weight reduction and good strength in automotive industry have drawn considerable interest in thixocasting technologies. Joining of such components with conventional fusion welding creates voids, hot cracking, distortion in shape, and more importantly evolution of dendritic microstructure that ultimately would lead to inferior mechanical properties of the weld region. Thus, the purpose of making thixocast component is lost. The friction welding which is a solid state joining process can avoid defects associated with melting and solidification in a typical fusion weld and can be a promising alternative. This process produces a weld under compressive force at the...

  8. Experimental and Numerical Investigation on Friction Welding of Thixocast A356 Aluminium Alloy

    Singh, Shailesh Kumar
    The challenges of weight reduction and good strength in automotive industry have drawn considerable interest in thixocasting technologies. Joining of such components with conventional fusion welding creates voids, hot cracking, distortion in shape, and more importantly evolution of dendritic microstructure that ultimately would lead to inferior mechanical properties of the weld region. Thus, the purpose of making thixocast component is lost. The friction welding which is a solid state joining process can avoid defects associated with melting and solidification in a typical fusion weld and can be a promising alternative. This process produces a weld under compressive force at the...

  9. Some Processing and Mechanical Behavior Related Issues in Ti-Ni Based Shape Memory Alloys

    Shastry, Vyasa Vikasa
    Shape memory alloys (SMAs) exhibit unique combination of structural and functional properties and hence have a variety of current and potential applications. The mechanical behaviour of SMAs, in particular the influence of processing on the microstructure, which in turn influences the performance of the alloy, mechanical properties at the nano-scale, and under cyclic loading conditions, are of great current interest. In this thesis, specific issues within each of these broad areas are examined with a view to suggest further optimize/characterize SMAs. They are the following: (a) For thermo-mechanical secondary processing of SMAs, can we identify the optimum combination of temperature-...

  10. Destabilisation and Failure of Cylindrical Nanopores : A Phase Field Study

    Joshi, Chaitanya
    Phase field models have played an important role in shaping our understanding of a variety of micro structural phenomena in materials. Their attractive features include (a) their ability to capture instabilities in microstructures, and (b) their ability to handle topological transitions { such as splitting or coalescence { gracefully. Therefore, we have chosen to use a phase field model in our study of instabilities in cylindrical pores in nanoporous membranes which eventually lead to their failure. Our study is motivated by recent studies on thermal stability of nanoporous membranes of alumina, titania and zirconia. The key feature in our model...

  11. Destabilisation and Failure of Cylindrical Nanopores : A Phase Field Study

    Joshi, Chaitanya
    Phase field models have played an important role in shaping our understanding of a variety of micro structural phenomena in materials. Their attractive features include (a) their ability to capture instabilities in microstructures, and (b) their ability to handle topological transitions { such as splitting or coalescence { gracefully. Therefore, we have chosen to use a phase field model in our study of instabilities in cylindrical pores in nanoporous membranes which eventually lead to their failure. Our study is motivated by recent studies on thermal stability of nanoporous membranes of alumina, titania and zirconia. The key feature in our model...

  12. Effect of Li Addition on the Plasticity of AZ31 Mg-Alloy

    Govind, *
    Mg-alloys, despite being the lightest structural metallic materials, find limited applications due to their poor workability, which is due to the hcp structure that does not provide sufficient number of independent slip systems for compatible deformation. Workability improves with the increase in the deformation temperature, when non-basal slip starts playing a larger role in deformation. Efforts were made to improve the workability through control of texture, grain refinement and alloying. Alloying activates non-basal slip by decreasing the critical resolved shear stress (CRSS) on non-basal planes or by promoting cross slip through an increase in the stacking fault energy (SFE) on...

  13. Effect of Li Addition on the Plasticity of AZ31 Mg-Alloy

    Govind, *
    Mg-alloys, despite being the lightest structural metallic materials, find limited applications due to their poor workability, which is due to the hcp structure that does not provide sufficient number of independent slip systems for compatible deformation. Workability improves with the increase in the deformation temperature, when non-basal slip starts playing a larger role in deformation. Efforts were made to improve the workability through control of texture, grain refinement and alloying. Alloying activates non-basal slip by decreasing the critical resolved shear stress (CRSS) on non-basal planes or by promoting cross slip through an increase in the stacking fault energy (SFE) on...

  14. Design & Fabrication of Bio-responsive Drug Carriers Based on Protamine & Chondroitin Sulphate Biopolymers

    Radhakrishnan, Krishna
    The present thesis focuses on the fabrication of bio-stimuli responsive micro- and nano-carriers for drug delivery applications. In particular, the objective of this work is to investigate the possibility of using polypeptide drug protamine and glycosaminoglycan drug, chondroitin sulphate as stimuli responsive components in the design of bioresponsive carriers. These biopolymers are biocompatible, biodegradable and clinically used for various applications. Two designs that incorporate these stimuli responsive components have been studied in this thesis. The first design involves hollow micro and nanocapsules that have been fabricated by incorporating the stimuli responsive biopolymers as wall components. Upon exposure to biological triggers, these...

  15. Design & Fabrication of Bio-responsive Drug Carriers Based on Protamine & Chondroitin Sulphate Biopolymers

    Radhakrishnan, Krishna
    The present thesis focuses on the fabrication of bio-stimuli responsive micro- and nano-carriers for drug delivery applications. In particular, the objective of this work is to investigate the possibility of using polypeptide drug protamine and glycosaminoglycan drug, chondroitin sulphate as stimuli responsive components in the design of bioresponsive carriers. These biopolymers are biocompatible, biodegradable and clinically used for various applications. Two designs that incorporate these stimuli responsive components have been studied in this thesis. The first design involves hollow micro and nanocapsules that have been fabricated by incorporating the stimuli responsive biopolymers as wall components. Upon exposure to biological triggers, these...

  16. Corrosion And Wear Behaviour of Plasma Electrolytic Oxidation And Laser Surface Alloy Coatings Produced on Mg Alloys

    Rapheal, George
    In the present investigation, surface coatings employing laser surface alloying (LSA) and plasma electrolytic oxidation (PEO) processes have been prepared on Mg alloys. The coatings have been investigated for corrosion and wear behaviour. Two important Mg alloys based on Mg–Al system were selected namely, MRI 230D and AM50 as substrates. LSA coatings have been prepared employing Al and Al2O3 as precursors using different laser scan speeds. PEO coatings were prepared in standard silicate and phosphate based electrolytes employing unipolar, pulsed DC. Hybrid coatings using a combination of the two processes were also produced and investigated for corrosion and wear behaviour....

  17. Corrosion And Wear Behaviour of Plasma Electrolytic Oxidation And Laser Surface Alloy Coatings Produced on Mg Alloys

    Rapheal, George
    In the present investigation, surface coatings employing laser surface alloying (LSA) and plasma electrolytic oxidation (PEO) processes have been prepared on Mg alloys. The coatings have been investigated for corrosion and wear behaviour. Two important Mg alloys based on Mg–Al system were selected namely, MRI 230D and AM50 as substrates. LSA coatings have been prepared employing Al and Al2O3 as precursors using different laser scan speeds. PEO coatings were prepared in standard silicate and phosphate based electrolytes employing unipolar, pulsed DC. Hybrid coatings using a combination of the two processes were also produced and investigated for corrosion and wear behaviour....

  18. Some Mechanical Properties of Ti-6Al-4V-B Alloys

    Singh, Gaurav
    The alloys of Ti are extensively used in a number of industries with the α+β alloy Ti-6Al-4V (referred to as Ti64 hereafter) being the most popular. Recently, it was demonstrated that the addition of a small amount of B – as small as 0.04 wt.% – results in an order-of-magnitude reduction in the as-cast grain size. Consequently, there is considerable current interest in understanding the mechanical behaviour of B-modified alloys, with particular emphasis on correlating the microstructural changes with the property variations and the deleterious effects – if any – of TiB particles especially in the context of fatigue. Prior...

  19. Some Mechanical Properties of Ti-6Al-4V-B Alloys

    Singh, Gaurav
    The alloys of Ti are extensively used in a number of industries with the α+β alloy Ti-6Al-4V (referred to as Ti64 hereafter) being the most popular. Recently, it was demonstrated that the addition of a small amount of B – as small as 0.04 wt.% – results in an order-of-magnitude reduction in the as-cast grain size. Consequently, there is considerable current interest in understanding the mechanical behaviour of B-modified alloys, with particular emphasis on correlating the microstructural changes with the property variations and the deleterious effects – if any – of TiB particles especially in the context of fatigue. Prior...

  20. Engineering Bioactive And Multifunctional Graphene Polymer Composites for Bone Tissue Regeneration

    Kumar, Sachin B
    The growing incidences of orthopedic problems globally have created a huge demand for strong bioactive materials for bone tissue engineering. Over the years, studies have shown chemical, physical, and mechanical properties of biomaterials influence the cellular interactions at the material-tissue interface, which subsequently controls biological response to materials. Strong biomaterials with surface properties that actively direct cellular response hold the key for engineering the next generation orthopedic implants. With its unique properties graphene can be used to reinforce poly (ε-caprolactone) (PCL) to prepare strong and bioactive polymer nanocomposites for bone tissue regeneration. The thesis entitled ―Engineering bioactive and multifunctional graphene...

Aviso de cookies: Usamos cookies propias y de terceros para mejorar nuestros servicios, para análisis estadístico y para mostrarle publicidad. Si continua navegando consideramos que acepta su uso en los términos establecidos en la Política de cookies.