Chapter 1- Introduction to Materials Science & Engineering Lesson Objective... Introduce fundamental concepts in MSE You will learn about: material structure how structure dictates properties how processing can change structure This course will help you to: use materials properly realize new design opportunities with materials a Chapter 1- Engineered structures are not blackboxes. They are made from raw materials which have a processed internal structure. This internal structure affects the material and The engineered structure properties... Structure Properties Processing Structure ProcessingProperties Chapter 1- Structural featureDimension (m) atomic bonding missing/extra atoms crystals (ordered atoms) and crystal defects second phase particles crystal texturing < > Structure has many dimensions Chapter 1- Understanding Size How big (small) are we talking about? Classical systems are macroscopic and nanosystems are nanoscopic. Chapter 1- Understanding Size 1 meter source: Glenn Fishbine - CERN Chapter 1- Understanding Size 10 centimeters source: Glenn Fishbine - CERN Chapter 1- Understanding Size 1 centimeter source: CERN Chapter 1- Understanding Size micrometers source: CERN Chapter 1- Understanding Size 10 micrometers source: CERN Chapter 1- Understanding Size 1 micrometer source: CERN Chapter 1- Understanding Size 100 nanometers source: CERN Chapter 1- Understanding Size 10 nanometers source: CERN Chapter 1- Understanding Size 1 nanometer source: CERN Chapter 1- Size Matters Its not just how big you are Its what you can do with it Chapter 1- Understanding Effects Physical processes do not scale uniformly gravity friction combustion electrostatic van der Walls brownian quantum Chapter 1- Understanding Effects Gravity Chapter 1- Understanding Effects Friction Chapter 1- Understanding Effects Combustion Chapter 1- Understanding Effects Electrostatic Chapter 1- Understanding Effects van der Waals Chapter 1- Understanding Effects brownian Chapter 1- Understanding Effects Quantum "I don't like it, and I'm sorry I ever had anything to do with it. - Erwin Schrodinger "I think that I can safely say that nobody understands quantum mechanics. - Richard Feynman Chapter 1- Understanding Size of Effects Centimeter: Gravity, friction, combustion, Newtonian mechanics Millimeter: Gravity, friction, combustion, electrostatic, magnetic Micrometer: Electrostatic, magnetic, van der Walls, Brownian Nanometer: Electrostatic, magnetic, van der Walls, Brownian, Quantum Angstrom: Quantum mechanics (1/10,000,000,000 meter) Chapter 1- ex: hardness vs structure of steel Properties depend on structure Data obtained from Figs (a) and with 4wt%C composition, and from Fig and associated discussion, Callister 6e. Micrographs adapted from (a) Fig ; (b) Fig. 9.27;(c) Fig ; and (d) Fig , Callister 6e. ex: structure vs cooling rate of steel Processing can change structure 2 Structure, Processing, & Property Hardness (BHN) Chapter Pick ApplicationDetermine 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, environment tolerance corrosion resistance. Material: structure, composition. 3 The Materials Selection Process Chapter 1- Electrical Resistivity of Copper: Adding impurity atoms to Cu increases resistivity. Deforming Cu increases resistivity. 4 Adapted from Fig. 18.8, Callister 6e. (Fig adapted from: J.O. Linde, Ann Physik 5, 219 (1932); and C.A. Wert and R.M. Thomson, Physics of Solids, 2nd edition, McGraw-Hill Company, New York, 1970.) ELECTRICAL Chapter 1- Space Shuttle Tiles: --Silica fiber insulation offers low heat conduction. Thermal Conductivity of Copper: --It decreases when you add zinc! 5 Fig. 19.0, Callister 6e. (Courtesy of Lockheed Missiles and Space Company, Inc.) Adapted from Fig. 19.4W, Callister 6e. (Courtesy of Lockheed Aerospace Ceramics Systems, Sunnyvale, CA) (Note: "W" denotes fig. is on CD-ROM.) Adapted from Fig. 19.4, Callister 6e. (Fig is adapted from Metals Handbook: Properties and Selection: Nonferrous alloys and Pure Metals, Vol. 2, 9th ed., H. Baker, (Managing Editor), American Society for Metals, 1979, p. 315.) THERMAL Chapter 1- Magnetic Permeability vs. Composition: --Adding 3 atomic % Si makes Fe a better recording medium! Adapted from C.R. Barrett, W.D. Nix, and A.S. Tetelman, The Principles of Engineering Materials, Fig. 1-7(a), p. 9, 1973.Electronically reproduced by permission of Pearson Education, Inc., Upper Saddle River, New Jersey. 6 Fig , Callister 6e. (Fig is from J.U. Lemke, MRS Bulletin, Vol. XV, No. 3, p. 31, 1990.) Magnetic Storage: --Recording medium is magnetized by recording head. MAGNETIC Chapter 1- Transmittance: --Aluminum oxide may be transparent, translucent, or opaque depending on the material structure. 7 Adapted from Fig. 1.2, Callister 6e. (Specimen preparation, P.A. Lessing; photo by J. Telford.) single crystal polycrystal: low porosity polycrystal: high porosity OPTICAL Chapter 1- Stress & Saltwater... --causes cracks! Heat treatment: slows crack speed in salt water! 4m4m --material: 7150-T651 Al "alloy" (Zn,Cu,Mg,Zr) Adapted from Fig (b), R.W. Hertzberg, "Deformation and Fracture Mechanics of Engineering Materials" (4th ed.), p. 505, John Wiley and Sons, (Original source: Markus O. Speidel, Brown Boveri Co.) 8 Adapted from Fig. 17.0, Callister 6e. (Fig is from Marine Corrosion, Causes, and Prevention, John Wiley and Sons, Inc., 1975.) Adapted from Fig , Callister 6e. (Fig provided courtesy of G.H. Narayanan and A.G. Miller, Boeing Commercial Airplane Company.) Enviromental Tolerance Chapter 1- Review: Mechanical Properties Stress vs. strain Hookes law E yy TS FF E Chapter 1- Tensile stress Chapter 1- Shear stress Chapter 1- Shear deformation Chapter Stress and Strain Stress: Force per unit area arising from applied load. Tension, compression, shear, torsion or any combination. Stress = = force/area Strain: physical deformation response of a material to stress, e.g., elongation. Chapter Simple tension: cable Simple shear: drive shaft Note: = M/A c R here. Ski lift (photo courtesy P.M. Anderson) Common States of Stress Chapter Simple compression: Note: compressive structural member ( < 0). (photo courtesy P.M. Anderson) Common States of Stress Chapter Elastic Deformation Elastic means reversible! F Linear- elastic Non-Linear- elastic 2. Small load F bonds stretch 1. Initial3. Unload return to initial Chapter Plastic Deformation of Metals Plastic means permanent! 1. Initial2. Small load3. Unload planes still sheared F elastic + plastic bonds stretch & planes shear plastic elastic F linear elastic linear elastic plastic Chapter Tensile specimen Other types: -compression: brittle materials (e.g., concrete) -torsion: cylindrical tubes, shafts. Tensile test machine Strain Testing Often 12.8 mm x 60 mm specimen extensometer Adapted from Fig. 7.2, Callister & Rethwisch 3e. gauge length Chapter 1- Use the right material for the job. Understand the relation between structure, properties, and processing. Recognize new design opportunities offered by materials selection. Lesson Goals: 9 SUMMARY