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  • Metals have high thermal & electrical conductivity because valence electrons are free to roam <br />

Rev materials science &_engineering_a. lal Rev materials science &_engineering_a. lal Presentation Transcript

  • MATERIALS SCIENCEMATERIALS SCIENCE && METTALURGYMETTALURGY Dr. Achchhe Lal Department of Mechanical Engineering SVNIT Surat-395007 Phone: (+91) (261) 2201993, Mobile: 9824442503 Email: lalachchhe@yahoo.co.in, URL: http://www.svnit.ac.inKindly send your comments and feedback for improvement at this email address Projectcoordination
  • Basic References Materials Science and Engineering (5th Edition) V. Raghavan Prentice-Hall of India Pvt. Ltd., 2004. Callister's Materials Science and Engienering William D Callister (Adapted by R. Balasubramaniam) Wiley Inida (P) Ltd., 2007. The Science and Engineering of Materials Donald. R. Askeland & Pradeep Phulé Cengage Learning, 2006.
  •  Introduction to diverse kinds of engineering materials  Overview of what determines the properties of materials and how we engineer them  Structure of materials and various lengthscales: crystal structure, electromagnetic structure, defect structure, microstructure…  Stability and metastability of materials: the thermodynamics and kinetics  The tools used in materials science: x-ray diffraction, phase diagrams, TTT diagrams…  Properties of materials: elasticity, plasticity, fracture, fatigue, creep, conduction, magnetism… What will you learn?What will you learn? “A teacher’s job is to uncover and not cover the syllabus”- Richard M Felder
  • The following hyperlinks are to file-wise substructure. Content-wise substructure will appear in respective chapters.The following hyperlinks are to file-wise substructure. Content-wise substructure will appear in respective chapters. 1. CHAPTER 1: Introduction 1.1 Introduction to Materials 1.2 Hierarchy of Lengths scales 1. CHAPTER 1: Introduction 1.1 Introduction to Materials 1.2 Hierarchy of Lengths scales CHAPTER 2: CLASSIFICATION OF MATERIALS AND METALS Semiconductor, magnetic dielectric, Superconductor, nanomaterials, engineering alloy and steel , cost Irons and nonferrous materials CHAPTER 2: CLASSIFICATION OF MATERIALS AND METALS Semiconductor, magnetic dielectric, Superconductor, nanomaterials, engineering alloy and steel , cost Irons and nonferrous materials 3. CHAPTER 3: POLYMERS, CERAMICS & COMPOSITES Definition, Classification & characteristics of polymers, Types of polymerization, Polymer processing, Elastomers, Properties of ceramic materials, Cermets, Composite mate rials, Fiber reinforced plastic (FRP) 3. CHAPTER 3: POLYMERS, CERAMICS & COMPOSITES Definition, Classification & characteristics of polymers, Types of polymerization, Polymer processing, Elastomers, Properties of ceramic materials, Cermets, Composite mate rials, Fiber reinforced plastic (FRP) 4. CHAPTER 4: PHASE DIAGRAM Objectives & classification, System, phases & structural constituent of phase diagram, Coring & dendritic segregation, Gibb’s, solid phase rule, Eutectic, Peritectic & eutec toid system, Equilibrium diagrams for non - ferrous alloys, Lever rule. 4. CHAPTER 4: PHASE DIAGRAM Objectives & classification, System, phases & structural constituent of phase diagram, Coring & dendritic segregation, Gibb’s, solid phase rule, Eutectic, Peritectic & eutec toid system, Equilibrium diagrams for non - ferrous alloys, Lever rule. 5. CHAPTER 5: HEAT TREATMENT PROCESSES Definition, Purpose & classification of heat treatment processes for various types of special steels, Introduction & applications of various case hardening & surface hardening treatments. TTT & CCT curves 5. CHAPTER 5: HEAT TREATMENT PROCESSES Definition, Purpose & classification of heat treatment processes for various types of special steels, Introduction & applications of various case hardening & surface hardening treatments. TTT & CCT curves 6. CHAPTER 6: MECHANICAL BEHAVIOR OF METALS properties of metals, Deformation of metals, Mechanisms of deformation, Deformation in polycrystalline materials, Mechanical testing of materials (destructive & non -destructive testing methods). 6. CHAPTER 6: MECHANICAL BEHAVIOR OF METALS properties of metals, Deformation of metals, Mechanisms of deformation, Deformation in polycrystalline materials, Mechanical testing of materials (destructive & non -destructive testing methods).
  • 5 Objectives of Chapter 1  Introduce the field of materials science and engineering (MSE)  Provide introduction to the classification of materials
  • 6 Chapter Outline  1.1 What is Materials Science and Engineering?  1.2 Classification of Materials  1.3 Functional Classification of Materials  1.4 Classification of Materials Based on Structure  1.5 Environmental and Other Effects  1.6 Materials Design and Selection
  • Introduction to Materials Science •Material Science: Science of materials means “knowledge of material which help the engineers and technologist to make best and efficient use of material to serve need of modern civilization”. •In Short: Material science doesn’t mean just knowing the physics and chemistry of the material, their behavior and properties, but also it is essential to know how material can be suitably, efficiently and economically put to the practical use under wide range of conditions. •The conditions may be related to the operation, to the fabrication and/or to the stability to the materials in order to develop, prepare modify and apply material to specific need. •Materials are available in solid, liquid and gaseous form. However the scope of materials are restricted to the study of solid materials those are useful to the to the engineering.
  • • Four Major Components of Material Science and Engineering: • Structure of Materials • Properties of Materials • Processing of Materials • Performance of Materials • The ability to understand the relationships between these factors has been crucial to most of mankind‘s technological breakthroughs.
  • 9 © 2003 Brooks/Cole Publishing / Thomson Learning™ Introduction to Chapter 1
  • 10 ©2003Brooks/ColePublishing/ThomsonLearning™ Figure 1.1 Application of the tetrahedron of materials science and engineering to ceramic superconductors. Note that the microstructure- synthesis and processing-composition are all interconnected and affect the performance-to-cost ratio
  • 11 Figure 1.2 Application of the tetrahedron of materials science and engineering to sheet steels for automotive chassis. Note that the microstructure-synthesis and processing-composition are all interconnected and affect the performance-to- cost ratio ©2003Brooks/ColePublishing/ThomsonLearning™
  • 12 ©2003Brooks/ColePublishing/ThomsonLearning™ Figure 1.3 Application of the tetrahedron of materials science and engineering to semiconducting polymers for microelectronics
  • 6 Ao Ad force die blank force • Forging (wrenches, crankshafts) CASTING JOININGFORMING • Drawing (rods, wire, tubing) often at elev. T • Rolling (I-beams, rails) • Extrusion (rods, tubing) Adapted from Fig. 11.7, Callister 6e. ram billet container container force die holder die Ao Adextrusion roll Ao Ad roll tensile force Ao Addie die METAL FABRICATION METHODS-I
  • plaster die formed around wax prototype FORMING JOINING 8 CASTING • Sand Casting (large parts, e.g., auto engine blocks) Sand Sand molten metal • Investment Casting (low volume, complex shapes e.g., jewelry, turbine blades) wax • Die Casting (high volume, low T alloys) • Continuous Casting (simple slab shapes) molten solidified METAL FABRICATION METHODS-II
  • 7 • Hot working --recrystallization --less energy to deform --oxidation: poor finish --lower strength • Cold working --more energy to deform --oxidation: good finish --higher strength • Cold worked microstructures --generally are very anisotropic! --Forged --Fracture resistant! (a) (b) (c) --Swaged FORMING TEMPERATURE
  • 9 CASTINGFORMING JOINING • Powder Processing (materials w/low ductility) pressure heat point contact at low T densification by diffusion at higher T area contact densify • Welding (when one large part is impractical) • Heat affected zone: (region in which the microstructure has been changed). Adapted from Fig. 11.8, Callister 6e. (Fig. 11.8 from Iron Castings Handbook, C.F. Walton and T.J. Opar (Ed.), 1981.) piece 1 piece 2 fused base metal filler metal (melted) base metal (melted) unaffectedunaffected heat affected zone METAL FABRICATION METHODS-III
  • 10 Annealing: Heat to Tanneal, then cool slowly. Types of Annealing • Process Anneal: Negate effect of cold working by (recovery/ recrystallization) • Stress Relief: Reduce stress caused by: -plastic deformation -nonuniform cooling -phase transform. • Normalize (steels): Deform steel with large grains, then normalize to make grains small. • Full Anneal (steels): Make soft steels for good forming by heating to get γ, then cool in furnace to get coarse P. • Spheroidize (steels): Make very soft steels for good machining. Heat just below TE & hold for 15-25h. Based on discussion in Section 11.7, Callister 6e. THERMAL PROCESSING OF METALS
  • 11 • Ability to form martensite • Jominy end quench test to measure hardenability. • Hardness versus distance from the quenched end. 24°C water specimen (heated to γ phase field) flat ground 4” 1” Hardness,HRC Distance from quenched end Adapted from Fig. 11.10, Callister 6e. (Fig. 11.10 adapted from A.G. Guy, Essentials of Materials Science, McGraw-Hill Book Company, New York, 1978.) Adapted from Fig. 11.11, Callister 6e. HARDENABILITY--STEELS
  • Metals Nonmetals Ceramic Polymer Materials Composite Classification of Materials Ferrous metals Non ferrous metals Magnetic Materials Semiconductor Superconductor dielectric Bio Materials Future Materials Smart Materials Nanomaterial Steel CI PCS Alloy
  • Monolithic MaterialsMaterials Hybrids Ceramics & Glasses Metals (& Alloys) Polymers (& Elastomers) Sandwich Composite Lattice Segment Composites: have two (or more) solid components; usually one is a matrix and other is a reinforcement Sandwich structures: have a material on the surface (one or more sides) of a core material Lattice* Structures: typically a combination of material and space (e.g. metallic or ceramic forms, aerogels etc.). Segmented Structures: are divided in 1D, 2D or 3D (may consist of one or more materials). *Note: this use of the word 'lattice' should not be confused with the use of the word in connection with crystallography. Hybrids are designed to improve certain properties of monolithic materials
  • Common type of materials Metals Ceramics Polymers Hybrids (Composites)  Let us consider the common types of Engineering Materials.  These are Metals, Ceramics, Polymers and various types of composites of these.  A composite is a combination of two or more materials which gives a certain benefit to at least one property → A comprehensive classification is given in the next slide. The term Hybrid is a superset of composites.  The type of atomic entities (ion, molecule etc.) differ from one class to another, which in turn gives each class a broad ‘flavour’ of properties. ● Like metals are usually ductile and ceramics are usually hard & brittle ● Polymers have a poor tolerance to heat, while ceramics can withstand high temperatures ● Metals are opaque (in bulk), while silicate glasses are transparent/translucent ● Metals are usually good conductors of heat and electricity, while ceramics are poor in this aspect. ● If you heat semi-conductors their electrical conductivity will increase, while for metals it will decrease ● Ceramics are more resistant to harsh environments as compared to Metals  Biomaterials are a special class of materials which are compatible with the body of an organism (‘biocompatible’). Certain metals, ceramics, polymers etc. can be used as biomaterials. A Common Perspective & Glasses Diamond is poor electrical conductor but a good thermal conductor!! (phonons are responsible for this) Bonding and structure are key fac
  • Common materials: with various ‘viewpoints’ Glass: amorphous Ceramics Crystal Graphite PolymersMetals
  •  Metals and alloys  Cu, Ni, Fe, NiAl (intermetallic compound), Brass (Cu-Zn alloys)  Ceramics (usually oxides, nitrides, carbides)  Alumina (Al2O3), Zirconia (Zr2O3)  Polymers (thermoplasts, thermosets) (Elastomers) Polythene, Polyvinyl chloride, Polypropylene Common materials: examples Based on Electrical Conduction  Conductors  Cu, Al, NiAl  Semiconductors  Ge, Si, GaAs  Insulators  Alumina, Polythene* Based on Ductility  Ductile  Metals, Alloys  Brittle  Ceramics, Inorganic Glasses, Ge, Si * some special polymers could be conducting
  •  Based on state (phase) a given material can be Gas, Liquid or Solid (based on the thermodynamic variables: P, T,…). Intermediate/coexistent states are also possible (i.e clear demarcations can get blurred). (Kinetic variables can also affect how a material behaves: e.g. at high strain rates some materials may behave as solids and as a liquid at low strain rates)  Based on structure (arrangement of atoms/molecules/ions) materials can be Crystalline, Quasicrystalline or Amorphous. Intermediate states (say between crystalline and amorphous; i.e. partly crystalline) are also possible. Polymers are often only partly crystalline.  Liquid Crystals (‘in some sense’) are between Liquids and Crystals.  Based on Band Structure we can classify materials into Metals, Semi-metals, Semiconductors and Insulators.  Based on the size of the entity in question we can Nanocrystals, Nanoquasicrystals etc.
  •  In the next two slides we will traverse across lengthscales to demarcate the usual domain of Materials Science.  Many of the terms and concepts in the slide will be dealt with in later chapters  As we shall see the scale of Microstructures is very important and in some sense Materials Scientists are also ‘Microstructure Engineers’!  There could be issues involved at the scale of the component (i.e. design of the component or its meshing with the reminder of the system), which are traditionally not included in the domain of Materials Science. E.g. sharp corners in a component would lead to stress concentration during loading, which could lead to crack initiation and propagation, leading to failure of the component. ● The inherent resistance of the material to cracks (and stress concentrations) would typically be of concern to materials scientists and not the design of the component.
  • Atom Structure Crystal Electro- magnetic Microstructure Component Thermo-mechanical Treatments Phases Defects+ • Casting • Metal Forming • Welding • Powder Processing • Machining • Vacancies • Dislocations • Twins • Stacking Faults • Grain Boundaries • Voids • Cracks + Residual Stress Processing determines shape and microstructure of a component & their distribution Materials ScienceMaterials Science Please spend time over this figure and its implications (notes in the next slide) (Notes in the next slide)
  •  Structure could imply two types of structure:  Crystal structure  Electromagnetic structure  Fundamentally these aspects are two sides of the same coin  Microstructure can be defined as: (Phases + Defect Structure + Residual Stress) and their distributions (more about these in later chapters)  Microstructure can be ‘tailored’ by thermo-mechanical treatments  A typical component/device could be a hybrid with many materials and having multiple microstructures E.g. a pen cap can have plastic and metallic parts
  • What determines the properties of materials? Funda Check  There are microstructure ‘sensitive’ properties (often called structure sensitive properties) and microstructure insensitive properties (note the word is sensitive and not dependent).   Microstructure ‘sensitive’ properties → Yield stress, hardness, Magnetic coercivity…  Microstructure insensitive properties → Density, Elastic modulus…  Hence, one has to keep in focus:  Atomic structure  Electromagnetic structure/Bonding  Microstructure to understand the properties.
  • MATERIALS SCIENCE & ENGINEERINGMATERIALS SCIENCE & ENGINEERING PHYSICAL MECHANICAL ELECTRO- CHEMICAL TECHNOLOGICAL • Extractive • Casting • Metal Forming • Welding • Powder Metallurgy • Machining • Structure • Physical Properties Science of Metallurgy • Deformation Behaviour • Thermodynamics • Chemistry • Corrosion  The broad scientific and technological segments of Materials Science are shown in the diagram below.  To gain a comprehensive understanding of materials science, all these aspects have to be studied.
  •  What determines the properties of materials?  Cannot just be the composition!  Few 10s of ppm of Oxygen in Cu can degrade its conductivity  Cannot just be the amount of phases present!  A small amount of cementite along grain boundaries can cause the material to have poor impact toughness  Cannot just be the distribution of phases!  Dislocations can severely weaken a crystal  Cannot just be the defect structure in the phases present!  The presence of surface compressive stress toughens glass Composition Phases & Their Distribution Defect Structure Residual Stress Hence, one has to traverse across lengthscales and look at various aspects to understand the properties of materials  The following factors put together determines the properties of a material:  Composition  Phases present and their distribution  Defect Structure (in the phases and between the phases)  Residual stress (can have multiple origins and one may have to travel across lengthscales)  These factors do NOT act independent of one another (there is an interdependency) Click here to ‘understand stress’Click here to ‘understand stress’
  • Properties influenced by Atomic structure Electromagnetic structure (Bonding characteristics)  Properties of a material are determined by two important characteristics:  Atomic structure  Electromagnetic structure – the bonding character (Bonding in some sense is the simplified description of valence electron density distributions)
  •  The goal of Materials Science and Engineering is to design materials with a certain set of properties, which gives a certain desired performance. Using suitable processing techniques the material can be synthesized and processed. The processing also determines the microstructure of the material.  To understand the microstructure the material scientist has to traverse across lengthscales and has to comprehend the defect structure in the material along with the phases and their distribution. The residual stress state in the material is also very important.  Common types of materials available to an engineer are: Metals, Ceramics and Polymers. A hybrid made out of these materials may serve certain engineering goals better.  Materials are also classified based on Band Structure (Metals, Semi-metals, Semiconductors, Insulators) or Atomic Structure (Crystals, Quasicrystals, Amorphous phases). Summary
  • “fundamental” Materials • Metals: – Strong, ductile, toughness – high thermal & electrical conductivity – opaque, reflective. – Examples: Iron/Steel, Aluminum, Copper, Titanium, Nickel • Polymers/plastics: Covalent bonding  sharing of e’s – Soft, ductile, low strength, low density, less dense than metals or ceramics, resist atmospheric and other forms of corrosion – thermal & electrical insulators – Optically translucent or transparent. – Examples: Plastics, Wood, Cotton (rayon, nylon), “glue”, polyethylene – Types: Thermoplastics plastics (usually soft and melt when heated and easy to be recycled), Thermo-set plastics (usually stiff and burn when heated and not easy to be recycled), Elastomers (flexible (rubbers)) • Ceramics: ionic bonding (refractory) – compounds of metallic & non-metallic elements (oxides, carbides, nitrides, sulfides) – Brittle, glassy, elastic, excellent strength and hardness properties – non-conducting (insulators), more resistant to high temperatures – Structural clay products, Whitewares, Refractories, Glasses, Cements
  • Fe3C cementite Metal Alloys Steels Ferrous Nonferrous Cast Irons Cu Al Mg Ti <1.4wt%C 3-4.5wt%C 1600 1400 1200 1000 800 600 400 0 1 2 3 4 5 6 6.7 L γ austenite γ+L γ+Fe3C α ferrite α+Fe3C α+γ L+Fe3C δ (Fe) Co, wt% C Eutectic: Eutectoid: 0.77 4.30 727°C 1148°C T(°C) Steels <1.4wt%C Cast Irons 3-4.5wt%C microstructure: ferrite, graphite cementite
  • Low Alloy High Alloy low carbon <0.25wt%C med carbon 0.25-0.6wt%C high carbon 0.6-1.4wt%C Uses auto struc. sheet bridges towers press. vessels crank shafts bolts hammers blades pistons gears wear applic. wear applic. drills saws dies high T applic. turbines furnaces V. corros. resistant Example 1010 4310 1040 4340 1095 4190 304 Additions none Cr,V Ni, Mo none Cr, Ni Mo none Cr, V, Mo, W Cr, Ni, Mo plain HSLA plain heat treatable plain tool austentitic stainless Name Hardenability 0 + + ++ ++ +++ 0 TS - 0 + ++ + ++ 0 EL + + 0 - - -- ++ increasing strength, cost, decreasing ductility STEELS
  • NonFerrous Alloys • Cu Alloys Brass: Zn is subst. impurity (costume jewelry, coins, corrosion resistant) Bronze: Sn, Al, Si, Ni are subst. impurity (bushings, landing gear) Cu-Be: precip. hardened for strength • Al Alloys -lower ρ: 2.7g/cm3 -Cu, Mg, Si, Mn, Zn additions -solid sol. or precip. strengthened (struct. aircraft parts & packaging) • Mg Alloys -very low ρ: 1.7g/cm3 -ignites easily -aircraft, missles • Refractory metals -high melting T -Nb, Mo, W, Ta• Noble metals -Ag, Au, Pt -oxid./corr. resistant • Ti Alloys -lower ρ: 4.5g/cm3 vs 7.9 for steel -reactive at high T -space applic. NONFERROUS ALLOYS
  • Properties •Light weight •greater stiffness and strength •Higher operating temperature •Excellent corrosion resistant •Very good fatigue characteristics •Ability to Tailor the structural properties according to requirements •design flexibility •Higher reliability, durability and affordability •Dissimilar materials •Differing in forms •Insoluble to each other •Physically distinct •Chemically inhomogeneous
  • Monolithic MaterialsMaterials Hybrids Ceramics & Glasses Metals (& Alloys) Polymers (& Elastomers) Sandwich Composite Lattice Segment Composites: have two (or more) solid components; usually one is a matrix and other is a reinforcement Sandwich structures: have a material on the surface (one or more sides) of a core material Lattice* Structures: typically a combination of material and space (e.g. metallic or ceramic forms, aerogels etc.). Segmented Structures: are divided in 1D, 2D or 3D (may consist of one or more materials). *Note: this use of the word 'lattice' should not be confused with the use of the word in connection with crystallography. Hybrids are designed to improve certain properties of monolithic materials
  •  Metals and alloys  Cu, Ni, Fe, NiAl (intermetallic compound), Brass (Cu-Zn alloys)  Ceramics (usually oxides, nitrides, carbides)  Alumina (Al2O3), Zirconia (Zr2O3)  Polymers (thermoplasts, thermosets) (Elastomers) Polythene, Polyvinyl chloride, Polypropylene Common materials: examples Based on Electrical Conduction  Conductors  Cu, Al, NiAl  Semiconductors  Ge, Si, GaAs  Insulators  Alumina, Polythene* Based on Ductility  Ductile  Metals, Alloys  Brittle  Ceramics, Inorganic Glasses, Ge, Si * some special polymers could be conducting
  • The Materials Tetrahedron  A materials scientist has to consider four ‘intertwined’ concepts, which are schematically shown as the ‘Materials Tetrahedron’.   When a certain performance is expected from a component (and hence the material constituting the same), the ‘expectation’ is put forth as a set of properties.  The material is synthesized and further made into a component by a set of processing methods (casting, forming, welding, powder metallurgy etc.).  The structure (at various lengthscales*) is determined by this processing.  The structure in turn determines the properties, which will dictate the performance of the component.  Hence each of these aspects is dependent on the others. The Materials Tetrahedron * this aspect will be considered in detail later The broad goal of Materials Science is toThe broad goal of Materials Science is to understand and ‘engineer’ this tetrahedronunderstand and ‘engineer’ this tetrahedron
  • January 21, 2014
  • The Materials Selection Process 1. Pick Application Determine required Properties 2. Properties Identify candidate Material(s) 3. Material Identify required Processing Processing: changes structure and overall shape ex: casting, sintering, vapor deposition, doping forming, joining, annealing. Properties: mechanical, electrical, thermal, magnetic, optical, deteriorative. Material: structure, composition.
  • 51 Section 1.2 Classification of Materials  Metals and Alloys  Ceramics, Glasses,and Glass-ceramics  Polymers (plastics), Thermoplastics and Thermosets  Semiconductors  Composite Materials
  • • Ceramics are used in a wide range of technologies such as refractories, spark plugs, dielectrics in capacitors, sensors, abrasives, magnetic recording media, etc.The space shuttle makes use of ~25,000 reusable, lightweight, highly porous ceramic tiles that protect the aluminum frame from the heat generated during re-entry into the Earth’s atmosphere.
  • 59 Table 1.1 Representative examples, applications, and properties for each category of materials Example of Applications Properties Metals and Alloys Gray cast iron Automobile engine blocks Castable, machinable, vibration damping Ceramics and Glasses SiO2-Na2O-CaO Window glass Optically transparent, thermally insulating Polymers Polyethylene Food packaging Easily formed into thin, flexible, airtight film
  • 60 Example of Applications Properties Semiconductors Silicon Transistors and integrated Unique electrical circuits behavior Composites Carbide cutting tools for High hardness, yet Tungsten carbide machining good shock resistance -cobalt (WC-Co) Table 1.1 Continued
  • 61 ©2003Brooks/ColePublishing/ThomsonLearning™ Figure 1.4 Representative strengths of various categories of materials
  • 62 Figure 1.5 A section through a jet engine. The forward compression section operates at low to medium temperatures, and titanium parts are often used. The rear combustion section operates at high temperatures and nickel- based superalloys are required. The outside shell experiences low temperatures, and aluminum and composites are satisfactory. (Courtesy of GE Aircraft Engines.) Figure 1.6 A variety of complex ceramic components, including impellers and blades, which allow turbine engines to operate more efficiently at higher temperatures. (Courtesy of Certech, Inc.)
  • 63 ©2003Brooks/ColePublishing/ThomsonLearning™ Figure 1.7 Polymerization occurs when small molecules, represented by the circles, combine to produce larger molecules, or polymers. The polymer molecules can have a structure that consists of many chains that are entangled but not connected (thermoplastics) or can form three-dimensional networks in which chains are cross-linked (thermosets)
  • 64 Figure 1.8 Polymers are used in a variety of electronic devices, including these computer dip switches, where moisture resistance and low conductivity are required. Figure 1.9 Integrated circuits for computers and other electronic devices rely on the unique electrical behavior of semiconducting materials. Figure 1.10 The X-wing for advanced helicopters relies on a material composed of a carbon- fiber-reinforced polymer.
  • January 22, 2014
  • 66 Performance (durability, reliability, properties and behavior under different environmental conditions  Aerospace  Biomedical (Bio Materials)  Electronic Materials  Energy Technology and Environmental Technology  Magnetic Materials  Photonic or Optical Materials  Smart Materials  Structural Materials Nano Materials Section 1.3 Functional Classification of Materials
  • ©2003Brooks/ColePublishing/ThomsonLearning™ Figure: Functional classification of materials. Notice that metals, plastics, and ceramics occur in different categories. A limited number of examples in each category is provided
  • Yttrium aluminium garnet (YAG is a synthetic crystalline material), Indium tin oxide (ITO) is one of the most widely used transparent conducting oxides because of its two chief properties, its electrical conductivity and optical transparency Gallium arsenide (GaAs) is a compound of the elements gallium and arsenic. It is a III/V semiconductor, and is used in the manufacture of devices such as microwave frequency integrated circuits, monolithic microwave integrated circuits, infrared light- emitting diodes, laser diodes, solar cells and optical windows. The nickel–zinc battery (sometimes abbreviated to the chemical symbols for the elements "NiZn") is a type of rechargeable battery that may be used in cordless power tools, cordless telephones, digital cameras, battery operated lawn and garden tools, professional photography, flashlights, electric bikes, and light electric vehicle sectors, among other uses. High initial magnetic permeability, low magnetic loss, and high electrical conductivity are the most advantages features of Mn–Zn ferrite as the main category of soft magnetic materials. Therefore Mn–Zn ferrites are mainly used as the cores for inductors, transformers, recording heads and in switchmode power supplies. (Co-Pt-Ta-Cr) alloys. Magnetic ferrites are used to make inductors and components for wireless communications
  • Structural Materials These materials are designed for carrying some type of stress. Steels, concrete, and composites are used to make buildings and bridges. Steels, glasses, plastics, and composites also are used widely to make automotives. Often in these applications, combinations of strength, stiffness, and toughness are needed under different conditions of temperature and loading. Smart Materials A smart material can sense and respond to an external stimulus such as a change in temperature, the application of a stress, or a change in humidity or chemical environment. Usually a smart material-based system consists of sensors and actuators that read changes and initiate an action.
  • An example of a passively smart material is lead zirconium titanate (PZT) and shape-memory alloys. When properly processed, PZT can be subjected to a stress, and a voltage is generated. This effect is used to make such devices as spark generators for gas grills and sensors that can detect underwater objects such as fish and submarines. Other examples of smart materials include magnetorheological or MR fluids. These are magnetic paints that respond to magnetic fields. These materials are being used in suspension systems of automobiles, including models by General Motors, Ferrari, and Audi. Still other examples of smart materials and systems are photochromic glasses and automatic dimming mirrors.
  • Photonic or Optical Materials Silica is used widely for making optical fibers. More than ten million kilometers of optical fiber have been installed around the world. Optical materials are used for making semiconductor detectors and lasers used in fiber optic communications systems and other applications. Similarly, alumina (Al2O3) and yttrium aluminum garnets (YAG) are used for making lasers. Amorphous silicon is used to make solar cells and photovoltaic modules. Polymers are used to make liquid crystal displays (LCDs). Magnetic Materials Computer hard disks make use of many ceramic, metallic, and polymeric materials. Computer hard disks are made using alloys based on cobalt-platinum-tantalum-chromium (Co-Pt-Ta-Cr) alloys. Many magnetic ferrites are used to make inductors and components for wireless communications. Steels based on iron and silicon are used to make transformer cores.
  • Electronic Materials As mentioned before, semiconductors, such as those made from silicon, are used to make integrated circuits for computer chips. Barium titanate (BaTiO3), tantalum oxide (Ta2O5), and many other dielectric materials are used to make ceramic capacitors and other devices. Superconductors are used in making powerful magnets. Copper, aluminum, and other metals are used as conductors in power transmission and in microelectronics. Biomedical Our bones and teeth are made, in part, from a naturally formed ceramic known as hydroxyapatite. A number of artificial organs, bone replacement parts, cardiovascular stents, orthodontic braces, and other components are made using different plastics, titanium alloys, and nonmagnetic stainless steels. Ultrasonic imaging systems make use of ceramics known as PZT (lead zirconium titanate). Magnets used for magnetic resonance imaging make use of metallic niobium tin-based superconductors.
  • Aerospace Light materials such as wood and an aluminum alloy (that accidentally strengthened the engine even more by picking up copper from the mold used for casting) were used in the Wright brothers’ historic flight. Today, NASA’s space shuttle makes use of aluminium powder for booster rockets. Aluminum alloys, plastics, silica for space shuttle tiles, and many other materials belong to this category.
  • A metallic material that is obtained by chemical combinations of different elements (e.g., steel is made from iron and carbon). Typically, alloys have better mechanical properties than pure metals. Alloy: Ceramics:A group of crystalline inorganic materials characterized by good strength, especially in compression, and high melting temperatures. Many ceramics have very good electrical and thermal insulation behavior Composites: A group of materials formed from mixtures of metals, ceramics, or polymers in such a manner that unusual combinations of properties are obtained (e.g., fiberglass) Composition: The chemical make-up of a material. Crystalline material:A material composed of one or many crystals. In each crystal, atoms or ions show a long-range periodic arrangement Density: Mass per unit volume of a material, usually expressed in units of g/cm3 or lb/in.3 Fatigue failure: Failure of a material due to repeated loading and unloading. Glass:An amorphous material derived from the molten state, typically, but not always, based on silica. Glass-ceramics: A special class of materials obtained by forming a glass and then heat treating it to form small crystals.
  • Regions between grains of a polycrystalline material.Grain boundaries: Grains: Crystals in a polycrystalline material Materials engineering: An engineering oriented field that focuses on how to transform materials into a useful device or structure. Materials science:A field of science that emphasizes studies of relationships between the microstructure, synthesis and processing, and properties of materials. Materials science and engineering (MSE): An interdisciplinary field concerned with inventing new materials and improving previously known materials by developing a deeper understanding of the microstructure-composition-synthesis processing relationships between different materials. Materials science and engineering tetrahedron: A tetrahedron diagram showing how the performance-to-cost ratio of materials depends upon the composition, microstructure, synthesis, and processing. Mechanical properties: Properties of a material, such as strength, that describe how well a material withstands applied forces, including tensile or compressive forces, impact forces, cyclical or fatigue forces, or forces at high temperatures.
  • An element that has metallic bonding and generally good ductility, strength, and electrical conductivity Metal : Microstructure : The structure of a material at the microscopic length scale. Physical properties : Characteristics such as color, elasticity, electrical or thermal conductivity, magnetism, and optical behavior that generally are not significantly influenced by forces acting on a material. Plastics : Polymers containing other additives. Polycrystalline material : A material composed of many crystals (as opposed to a single-crystal material that has only one crystal). Polymerization : The process by which organic molecules are joined into giant molecules, or polymers. Polymers : A group of materials normally obtained by joining organic molecules into giant molecular chains or networks. Polymers are characterized by low strengths, low melting temperatures, and poor electrical conductivity. Processing: Different ways for shaping materials into useful components or changing their properties. Semiconductors: A group of materials having electrical conductivity between metals and typical ceramics (e.g., Si, GaAs).
  • A crystalline material that is made of only one crystal (there are no grain boundaries). Single crystal : Smart material : A material that can sense and respond to an external stimulus such as change in temperature, application of a stress, or change in humidity or chemical environment. Strength-to-weight ratio : The strength of a material divided by its density; materials with a high strength-to-weight ratio are strong but lightweight. Structure : Description of the arrangements of atoms or ions in a material. The structure of materials has a profound influence on many properties of materials, even if the overall composition does not change.). Synthesis : The process by which materials are made from naturally occurring or other chemicals. Thermoplastics : A special group of polymers in which molecular chains are entangled but not interconnected. They can be easily melted and formed into useful shapes. Normally, these polymers have a chainlike structure (e.g., polyethylene). Thermosets : A special group of polymers that decompose rather than melt upon heating. They are normally quite brittle due to a relatively rigid, three- dimensional network structure (e.g., polyurethane).
  • 78 Section 1.4 Classification of Materials-Based on Structure  Crystalline material is a material comprised of one or many crystals. In each crystal, atoms or ions show a long-range periodic arrangement.  Single crystal is a crystalline material that is made of only one crystal (there are no grain boundaries).  Grains are the crystals in a polycrystalline material.  Polycrystalline material is a material comprised of many crystals (as opposed to a single-crystal material that has only one crystal).  Grain boundaries are regions between grains of a polycrystalline material.
  • 79 Environmental and Other Effects Effects of following factors must be accounted for in design to ensure that components do not fail unexpectedly:  Temperature  Corrosion  Fatigue  Strain Rate
  • 80 ©2003Brooks/ColePublishing/ThomsonLearning™ Figure 1.12 Increasing temperature normally reduces the strength of a material. Polymers are suitable only at low temperatures. Some composites, special alloys, and ceramics, have excellent properties at high temperatures
  • 81 ©2003Brooks/ColePublishing/ThomsonLearning™ Figure 1.13 Skin operating temperatures for aircraft have increased with the development of improved materials. (After M. Steinberg, Scientific American, October, 1986.)
  • 82 Figure 1-14 Schematic of a X-33 plane prototype. Notice the use of different materials for different parts. This type of vehicle will test several components for the Venturestar
  • 83 Section 1.6 Materials Design and Selection  Density is mass per unit volume of a material, usually expressed in units of g/cm3 or lb/in.3  Strength-to-weight ratio is the strength of a material divided by its density; materials with a high strength-to-weight ratio are strong but lightweight.
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  • Our role in engineering materials then is to understand the application and specify the appropriate material to do the job as a function of: Strength: yield and ultimate Ductility, flexibility Weight/density Working Environment Cost: Lifecycle expenses, Environmental impact* * Economic and Environmental Factors often are the most important when making the final decision!
  • Examples of Materials• Metals • Ferrous metals and alloys (irons, carbon steels, alloy steels, stainless steels, tool and die steels) • Nonferrous metals and alloys (aluminum, copper, magnesium, nickel, titanium, precious metals, refractory metals, superalloys) • Polymeric: Plastics, Wood, Cotton (rayon, nylon), “glue” • Thermoplastics plastics • Thermoset plastics • Elastomers • Ceramics • Glasses • Glass ceramics • Graphite • Diamond • Zirconia • Alumina, • Composites • Reinforced plastics • Metal-matrix composites • Ceramic-matrix composites • Sandwich structures • Concrete
  • • Metals have useful properties including strength, ductility, high melting points, thermal and electrical conductivity, and toughness. • From the periodic table, it can be seen that a large number of the elements are classified as being a metal. A few of the common metals and their typical uses are presented below. • Common Metallic Materials • Iron/Steel - Steel alloys are used for strength critical applications • Aluminum - Aluminum and its alloys are used because they are easy to form, readily available, inexpensive, and recyclable. • Copper - Copper and copper alloys have a number of properties that make them useful, including high electrical and thermal conductivity, high ductility, and good corrosion resistance. • Titanium - Titanium alloys are used for strength in higher temperature (~1000° F) application, when component weight is a concern, or when good corrosion resistance is required • Nickel - Nickel alloys are used for still higher temperatures (~1500-2000° F) applications or when good corrosion resistance is required. • Refractory materials are used for the highest temperature (> 2000° F) applications • The key feature that distinguishes metals from non-metals is their bonding. Metallic materials have free electrons that are free to move easily from one atom to the next. The existence of these free electrons has a number of profound consequences for the properties of metallic materials. For example, metallic materials tend to be good electrical conductors because the free electrons can move around within the metal so freely. More on the structure of metals will be discussed later. Metals
  • • The broad categories or segments that make up the ceramic industry can be classified as: • Structural clay products (brick, sewer pipe, roofing and wall tile, flue linings, etc.) • Whitewares (dinnerware, floor and wall tile, electrical porcelain, etc.) • Refractories (brick and monolithic products used in metal, glass, cements, ceramics, energy conversion, petroleum, and chemicals industries) • Glasses (flat glass (windows), container glass (bottles), pressed and blown glass (dinnerware), glass fibers (home insulation), and advanced/specialty glass (optical fibers)) • Abrasives (natural (garnet, diamond, etc.) and synthetic (silicon carbide, diamond, fused alumina, etc.) abrasives are used for grinding, cutting, polishing, lapping, or pressure blasting of materials) • Cements (for roads, bridges, buildings, dams, and etc.) • Advanced ceramics – Structural (wear parts, bioceramics, cutting tools, and engine components) – Electrical (capacitors, insulators, substrates, integrated circuit packages, piezoelectrics, magnets and superconductors) – Coatings (engine components, cutting tools, and industrial wear parts) – Chemical and environmental (filters, membranes, catalysts, and catalyst supports)
  • Properties •Light weight •greater stiffness and strength •Higher operating temperature •Excellent corrosion resistant •Very good fatigue characteristics •Ability to Tailor the structural properties according to requirements •design flexibility •Higher reliability, durability and affordability •Dissimilar materials •Differing in forms •Insoluble to each other •Physically distinct •Chemically inhomogeneous
  • •Most composites are made up of just two materials. One material (the matrix or binder) surrounds and binds together a cluster of fibres or fragments of a much stronger material (the reinforcement).
  • 1. Define materials science and engineering (MSE). Define the following terms: (a) composition, (b) structure, (c) synthesis, (d) processing, and (e) microstructure Explain the difference between the terms materials science and materials engineering 2. For each of the following classes of materials, give two specific examples that are a regular part of your life: (a) metals; (b) ceramics; (c) polymers; and (d) semiconductors. Specify the object that each material is found in and explain why the material is used in each specific application 3. Describe the enabling materials property of each of the following and why it is so: (a) silica tiles for the space shuttle; (b) steel for I-beams in skyscrapers; (c) a cobalt chrome molybdenum alloy for hip implants; (d) polycarbonate for eyeglass lenses; and (e) bronze for sculptures. Tutorial : 1
  • 5. Describe the enabling materials property of each of the following and why it is so: (a) aluminum for airplane bodies; (b) polyurethane for teeth aligners (invisible braces); (c) steel for the ball bearings in a bicycle’s wheel hub; (d) polyethylene terephthalate for water bottles; and (e) glass for wine bottles 6. Write one paragraph about why single crystal silicon is currently the material of choice for microelectronics applications. Write a second paragraph about potential alternatives to single-crystal silicon for solar cell applications.
  • 7. Steel is often coated with a thin layer of zinc if it is to be used outside. What characteristics do you think the zinc provides to this coated, or galvanized, steel? What precautions should be considered in producing this product? How will the recyclability of the product be affected? 8. Coiled springs ought to be very strong and stiff. Si3N4 is a strong, stiff material. Would you select this material for a spring? Explain. Temperature indicators are sometimes produced from a coiled metal strip that uncoils a specific amount when the temperature increases. How does this work; from what kind of material would the indicator be made; and what are the important properties that the material in the indicator must possess? 9. You would like to design an aircraft that can be flown by human power nonstop for a distance of 30 km. What types of material properties would you recommend? What materials might be appropriate? 10. You would like to place a three foot diameter microsatellite into orbit. The satellite will contain delicate electronic equipment that will send and receive radio signals from earth. Design the outer shell within which the electronic equipment is contained. What properties will be required, and what kind of materials might be considered?
  • 11. The hull of the space shuttle consists of ceramic tiles bonded to an aluminum skin. Discuss the design requirements of the shuttle hull that led to the use of this combination of materials. What problems in producing the hull might the designers and manufacturers have faced? 12. You would like to select a material for the electrical contacts in an electrical switching device that opens and closes frequently and forcefully. What properties should the contact material possess? What type of material might you recommend? Would Al2O3 be a good choice? Explain 13. Aluminum has a density of 2.7 g/cm3. Suppose you would like to produce a composite material based on aluminum having a density of 1.5 g/cm3. Design a material that would have this density. Would introducing beads of polyethylene, with a density of 0.95 g/cm3, into the aluminum be a likely possibility? Explain. 14. You would like to be able to identify different materials without resorting to chemical analysis or lengthy testing procedures. Describe some possible testing and sorting techniques you might be able to use based on the physical properties of materials
  • 15. You would like to be able to physically separate different materials in a scrap recycling plant. Describe some possible methods that might be used to separate materials such as polymers, aluminum alloys, and steels from one another. 16. Some pistons for automobile engines might be produced from a composite material containing small, hard silicon carbide particles in an aluminum alloy matrix. Explain what benefits each material in the composite may provide to the overall part. What problems might the different properties of the two materials cause in producing the part? 17. What is meant by the term composition of a material? What is meant by the term structure of a material? What are the different levels of structure of a material? Why is it important to consider the structure of a material while designing and fabricating engineering components? What is the difference between the microstructure and the macrostructure of a material?