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Introduction to materials science

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At the end of this section, students will be able to:-
• Identify with examples the different classes of
materials.
• Desc...

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Materials science: Studies the relationships that exist
between the structures and properties of materials.
Materials engi...

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It was built with the wrong steel (containing excessive ratios
of sulphur and phosphor) which undergo brittle fracture at ...

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Introduction to materials science

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Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are called alloys.
Metallurgy can also be described as the technology of metals, the way in which science is applied to the production of metals and the engineering of metal .

Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are called alloys.
Metallurgy can also be described as the technology of metals, the way in which science is applied to the production of metals and the engineering of metal .

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Introduction to materials science

  1. 1. At the end of this section, students will be able to:- • Identify with examples the different classes of materials. • Describe the distinctive chemical features of different materials. • Identify ‘Advanced Materials’ and how these differ from the classical material classes.
  2. 2. Materials science: Studies the relationships that exist between the structures and properties of materials. Materials engineering: Designing or engineering a material with a predetermined set of properties on the basis of the structure property correlations. Why should we know about materials? Because it is the job of the engineer to select materials for given application based of materials structure, properties, processing, performance and cost. What is Materials science and engineering?
  3. 3. It was built with the wrong steel (containing excessive ratios of sulphur and phosphor) which undergo brittle fracture at low temperature. Why did Titanic sink in 1912?
  4. 4. Fuel leakage in the rocket booster caused by a O-ring. The O-ring lost elasticity at low temperature. The Space Shuttle Challenger disaster:
  5. 5. Caused by metal fatigue of the wheels. Eschede train disaster:
  6. 6. Stone Age Ages of human development are called after important materials. Silicon Age Bronze Age Iron Age Concrete Now…? Polymer Age
  7. 7. Prehistoric hunting tools Hunting tools today
  8. 8. Combine Harvester today harvester's sickle, 3000 BC made from baked clay
  9. 9. Structure: The structure of a material is usually the arrangement of its internal components. Atomic structure: the organisation of atoms or molecules relative to one another. Microscopic structure: a larger structural realm, which contains large groups of atoms that are normally agglomerated together, which is subject to direct observation using some type of microscope. Macroscopic structure: comprises structural elements that may be viewed with the naked eye.
  10. 10. Properties: “A property is a material trait in terms of the kind and magnitude of response to a specific imposed stimulus.” Mechanical properties: for example, would relate deformation to an applied load or force; examples include elastic modulus and strength. Electrical properties: such as electrical conductivity and dielectric constant, the stimulus is an electric field. Thermal properties: measure for the behaviour of a material in response to temperature such as heat capacity and thermal conductivity.
  11. 11. Properties: “A property is a material trait in terms of the kind and magnitude of response to a specific imposed stimulus.” Magnetic properties: the response of a material to the application of a magnetic field. Optical properties: the stimulus is electromagnetic or light radiation. Index of refraction and reflectivity are representative optical properties.
  12. 12. Processing: The series of operations that transforms industrial materials from a raw-material state into finished parts or products. Performance: processing structure properties composition structure determines properties processing effects structure and structure determines processing routes processing influences properties and properties determines processing routes composition influences processing routes, structure & properties
  13. 13. Same material – aluminium oxide – different processing method – different structure Single crystal Polycrystalline made of very small single crystals Polycrystalline with pores Adapted from Fig. 1.2, Callister & Rethwisch 8e. (Specimen preparation, P.A. Lessing; photo by S. Tanner.)
  14. 14. Metals: Composed of one or more metallic elements (such as iron, aluminium, copper, titanium, gold, and nickel), and often also non- metallic elements (for example, carbon, nitrogen, and oxygen) in relatively small amounts. Atoms in metals and their alloys are arranged in a very orderly manner. Fig. 1.08 Callister & Rethwisch 8e. Properties: Stiff and strong, but ductile High thermal & electrical conductivity Opaque, reflective High density
  15. 15. Polymers (plastics or rubber): Many polymers are organic compounds that are chemically based on carbon, hydrogen, and other non-metallic elements (O, N, and Si). Inorganic polymers also exist such as silicon rubber. Very large molecular structures often chain-like in nature. Fig. 1.10 Callister & Rethwisch 8e. Properties: Soft, ductile, low strength, low density Thermal & electrical insulators Optically translucent or transparent
  16. 16. Ceramics: Compounds formed with metallic and non-metallic elements. They are most frequently oxides, nitrides, and carbides. Examples: aluminum oxide (or alumina, Al2O3), silicon dioxide (or silica, SiO2), silicon carbide (SiC), silicon nitride (Si3N4), clay minerals (i.e., porcelain), cement, and glass. Fig. 1.09 Callister & Rethwisch 8e. Properties: Brittle, glassy Strong Non-conducting (insulators) Optical characteristics – can be transparent, translucent, or opaque
  17. 17. Composites: A composite consist of two (or more) individual materials formed from metals, ceramics, and/or polymers. The design goal of a composite is to achieve a combination of properties that is not displayed by any single material, and also to incorporate the best characteristics of each of the component materials. Example: fibreglass Made of small glass fibres embedded within a polymeric material (epoxy). Properties: stiff, strong (from the glass) flexible, and ductile (from polymer)
  18. 18. Density Adapted from Fig. 1.03 Callister & Rethwisch 8e.
  19. 19. Stiffness Adapted from Fig. 1.04 Callister & Rethwisch 8e.
  20. 20. Materials that are utilized in high-technology: Typically traditional materials whose properties have been enhanced, newly developed, high-performance materials. Include all material types (e.g., metals, ceramics, polymers). Generally expensive. Examples include: materials that are used for lasers, integrated circuits, magnetic information storage, fibre optics, etc.
  21. 21. Semiconductors: Have electrical properties that are intermediate between the electrical conductors (metals and metal alloys) and insulators (ceramics and polymers). Examples: gallium arsenide, germanium. Biomaterials: Employed as components implanted into the human body for replacement of diseased or damaged body parts. Biocompatible - must not cause adverse biological reactions. Can be metals, ceramics, polymers, composites, or semiconductors.
  22. 22. Nano-engineered materials: Nanomaterials typically have sizes of below 100 nm (1 nm = 10-9m). At these dimensions materials can acquire novel properties (i.e. optical, mechanical, thermal). Example: Bulk silver and silver nanoparticles.
  23. 23. • Use the right material for the job. • Understand the relationship between properties, structure, and processing. • Recognise new design opportunities offered by materials selection.

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