Introduction to Material Sciences, Lecture 1

Material Science

1. Intro to Material Science Lecture 1 by Ch. Azmat Ali Minhas Chairman Department of Physics UOC Chakwal

2. Why Study Material Science Every scientist/engineer encounter problems in which they have to select materials Knowledge of properties of different materials comes handy for material selection

3. Materials used for coffee cup?

4. Material for airplane wing Should withstand high force (strong) Could bear cyclic application of force (fatigue property) Density and corrosion resistance Shock landing (impact), high temperature (creep) are not important W ood…Steel…Aluminum…Carbon Fiber

5. Optical properties are important Material must interact with light Must be resistant to corrosion and wear. What about solar cell on satellite? Material for solar cells

6. Type of Materials Metals (aluminum, magnesium, zinc, iron, nickel, steel etc ) Free electrons Metallic bonding Good conductivity, ductility, formability, shock resistance etc Used for electrical and structural or lead bearing application

7. Ceramics (brick, glass, tableware, insulators) Mostly ionic bonding or amorphous Complex structure Good strength and hardness Useful optical, electrical and thermal properties. Poor formability, ductility and shock resistance. They are less often used for structural or load-bearing applications Type of Materials

8. Semiconductors (Silicon, germanium, and gallium arsenide) Electrical conductivity between conductors and ceramics Electrical conductivity can be controlled by doping Used in integrated circuits Usually made out of molten materials Type of Materials

9. Polymers (rubber, plastic and adhesives) Organic (covalent bonging) Produced by creating polymerization of organic molecules (obtained from petroleum or agricultural products) Low electrical and thermal conductivity Some have excellent ductility, formability and shock resistance; other have opposite properties They are lightweight and have excellent resistance to corrosion Type of Materials

10. Composite Materials (concrete, plywood, fiberglass etc ) Have properties that cant be obtained by a single material With composites we can produce lightweight, strong, ductile, high temperature-resistant materials Functional Classification

11. Structure-Property-Processing Relationship Structure, property and processing and inter-related. If one is changed, one or both or the others change We must determine how the three interrelate.

12. Properties Mechanical How a material responds to applied stress Most common mechanical properties are strength, ductility and stiffness Impact, creep and wear are also important Small change in processing effects mechanical properties greatly.

13. Properties Physical Electrical, magnetic, optical, thermal, elastic and chemical behavior Depend both on structure and processing of material. Small change in composition profoundly changes conductivity of semiconductors and cermaics . High firing temp greatly reduces thermal insolation properties of ceramic bricks. Small amount of impurities change the color of gas or polymer

14. The structure can be considered on several levels all of which influences the behavior of product. Atoms Arrangement of atoms Grain structure Phases Structure

15. Processing Processing produce desire shape from initial formless material. e.g for metals, by pouring liquid into mold, by welding or using high pressures (forging, drawing, extraction, rolling, bending) Ceramic’s processing is done by heat treatment. Polymers are produced by injection of softened plastic into molds, drawing, forming.

16. Structure-Property-Processing Relationship The processing of the material effects structure e .g processing of copper by casting and forming leads to very different shapes, size and orientations of grains. Cast structure may contain voids

17. D uctility  is a solid material's ability to deform under tensile stress; this is often characterized by the material's ability to be stretched into a wire . Strength : the capacity of an object or substance to withstand great force or pressure Fatigue: weakness in metal or other materials caused by repeated variations of stress . Creep: exposed to high temp Wear: subjected to abrasive conditions Impact: exposure to sudden intense blow Casting: a manufacturing process by which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. Forming processes are particular manufacturing processes which make use of suitable stresses (like compression, tension, shear or combined stresses) to cause plastic deformation of the materials to produce required shapes.