Materials Science & Engineering PDF

Why Need to study Materials Science & Engineering ? Because There is no Engineering and Science without Materials. What are  Materials ? ❖ Materials are probably more deep-s...

Why Need to study Materials Science & Engineering ? Because There is no Engineering and Science without Materials. What are  Materials ? ❖ Materials are probably more deep-seated in our culture than most of us realize. Transportation, housing, clothing, communication, recreation, and food production virtually every segment of our everyday lives is influenced to one degree or another by materials. ❖ Historically, the development and advancement of societies have been intimately tied to the members’ ability to produce and manipulate materials to fill their needs. In fact, early civilizations have been designated by the level of their materials development (Stone Age, Bronze Age, Iron Age). ❖ The development of many technologies that make our existence so comfortable has been intimately associated with the accessibility of suitable materials. 2  Types of Materials ? ❖ Metals: – Strong, ductile – High thermal & electrical conductivity – Opaque, reflective. ❖ Polymers/plastics: – Soft, ductile, low strength, low density – Thermal & electrical insulators – Optically translucent or transparent. ❖ Ceramics: compounds of metallic & non-metallic elements (oxides, carbides, nitrides, sulfides) – Brittle, glassy,  – Non-conducting (insulators) 3 Classification of Materials: A Few Additional Categories Biomaterials implanted in human body compatible with body tissues Semiconductors electrical properties  between conductors and insulators electrical properties can be precisely controlled hip replacement Intel Pentium 4 4 Composite materials ❖ A composite is composed of two (or more) individual materials, which come  from the categories of metals, ceramics, and 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. 5 Materials Science & Engineering ❖ Sometimes it is useful to subdivide the discipline of materials science  and engineering into materials science and materials engineering sub disciplines. ❖ “materials science” involves investigating the relationships that exist between the structures and properties of materials. ❖ “materials engineering” is, on the basis of these structure–property correlations, designing or engineering the structure of a material to produce a predetermined set of properties. 6 Atomic Arrangement: Ordered vs. Disordered Crystalline: atoms are arranged in a 3D, periodic array giving the material “long range order” stacking can effect properties (i.e. ductility) anisotropic materials hexagonal close-packed Non-crystalline or amorphous: atoms only have short-range, nearest neighbor order viscous materials (generally complex formulas) or rapid cooling isotropic materials 7  Microstructure Polycrystalline Single Crystal the periodic arrangement of many small crystals or grains atoms extends throughout the small crystals misoriented with entire sample respect to on another difficult to grow, environment must several crystals are initiated and be tightly controlled grow towards each other anisotropic materials anisotropic or isotropic materials  8 Levels of Structure structure properties processing performance STRUCTURE (length scale)  < 0.2 nm 1-100 nm 1-100 μm > 1 mm 1 nm = ? 9 Length Scales of Material Science Atomic – < 10-10 m Nano – 10-9 m Micro – 10-6 m Macro – > 10-3 m 10  Crystal Systems Unit cell: smallest repetitive unit which contains the complete lattice pattern of a crystal. ❖ 7 crystal systems of varying symmetry are known ❖These systems are built by changing the lattice parameters: a, b, and c are the edge lengths α, β, and γ are interaxial angles Fig. 3.4, Callister 7e. 11 Crystal Systems 14 Crystal Systems 15 Atomic arrangement 16 Space lattice 17 Crystal systems  18 Crystal systems 19 Crystal systems 20 Crystal systems 21  Crystal systems 22 Crystal systems  23 Crystal Plane  24 Equivalent Planes 25 Coordination Number  12 26 Linear Density  27 Coordination Number  8 28 Atom per unit cell 29  Atomic packing factor (APF) 30  Atomic packing factor (APF)  31 Atomic packing factor (APF)  32 Point Defects  33 Point Defects 34 Point Defects  35 Point Defects 36 Point Defects  37 Line deffect  38 Line deffect  39 Line deffect 40 41 42 43 44 45