ME227 - Week 1.2 PDF

Chapter 1: Introduction to Materials Science & Engineering ISSUES TO ADDRESS... What is materials science and engineering? Why are materials important? Why is it important for engineers to understand materials ? Chapte...

Chapter 1: Introduction to Materials Science & Engineering ISSUES TO ADDRESS... What is materials science and engineering? Why are materials important? Why is it important for engineers to understand materials ? Chapter 1 1 What is Materials Science & Engineering? Materials science – Investigate relationships between structures and properties of materials – Design/develop new materials Materials engineering – Create products from existing materials – Develop materials processing techniques Chapter 1 2  Why Are Materials Important? Materials drive advancements in our society – Stone Age – Bronze Age – Iron Age What is today’s material age? – Silicon (Electronic Materials) Age? – Nanomaterials Age? – Polymer Age? Chapter 1 3  Why is it Important for Engineers to Understand Materials? Products/devices/components that engineers design are all made of materials To select appropriate materials and processing techniques for specific applications engineers must – have knowledge of material properties and – understand the structure- property relationships Chapter 1 4  Relationships Among Processing, Structure, & Properties Processing (e.g., cooling rate of steel from high temperature) affects structure (microstructure) Structure in turn effects hardness Structur (d) Propert 60 e y 0 30 μm (c) 50 Data obtained from Figs. 10.32(a) (b and Hardness 0 (a ) from 10.33Fig. 10e. with Micrographs 11.18, Callister 0.4 wt% composition, adapted and C & Rethwisch from (a) Fig. ) 4 μm 10.19; (BHN) 40 (b) Fig. 9.30; (c) Fig. 10.34; and (d) 30 Fig. 10.22, Callister & Rethwisch 10e. 0 30 μm (Figures 10.19, 10.22, & 10.34 copyright 1971 by United States Steel Corporation. μm Figure 9.30 courtesy of Republic Steel 30 10 Corporation.) 0 0.01 0.1 1 10 100 Processin 1000 g 20 Chapter 1 5 Cooling Rate (ºC/s)  Types of Materials Metals: – Strong, ductile – High thermal & electrical conductivities – Opaque, reflective Polymers/plastics: compounds of non-metallic elements – Soft, ductile, low strengths, low densities – Low thermal & electrical conductivities – Opaque, translucent or transparent Ceramics: compounds of metallic & non-metallic elements (oxides, carbides, nitrides, sulfides) – Hard, Brittle – Low thermal & electrical conductivities – Opaque, translucent, or transparent Chapter 1 6  Materials Selection Engineers often solve materials selection problems. Procedure: 1. For a Specific Application Determine Required Properties Properties: mechanical, electrical, thermal, magnetic, optical, deteriorative. 2. From List of Properties Identify Candidate Material(s) 3. Best Candidate Material Specify Processing technique(s) To provide required set of properties To produce component having desired Chapter 1 7  Material Property Types Properties of materials fall into six categories as follows: Mechanical Electrical Thermal Magnetic Optical Deteriorative Chapter 1 8  Mechanical Properties Affect of carbon content on the hardness of a common steel: Fig. 10.31, Callister & Rethwisch 10e. [Data taken from Metals Handbook: Heat 32 Treating, Vol. 4, 9th edition, V. Masseria 0 (Managing Editor), 1981. Reproduced by permission of ASM International, Materials Park, OH.] 24 hardness 0 Brinell 16 0 80 0 0.5 1wt %C Increasing carbon content increases hardness of steel. Chapter 1 9  Electrical Properties Factors that affect electrical resistivity – for copper: 6 Fig. 18.8, Callister & Rethwisch 9e. [Adapted from: J.O. Linde, Ann Physik 5, 5 219 (1932); and C.A. Wert and R.M. Thomson, Physics of Solids, 2nd edition, McGraw-Hill Company, New York, 1970.] (10-8 Ohm-m) Resistivity, 4 3 2 ρ 1 0 -200 -100 T (°C) Increasing 0temperature increases resistivity. Increasing impurity content (e.g., Ni) increases resistivity. Deformation increases resistivity. Chapter 1 10  Thermal Properties Thermal Conductivity – measure of a material’s ability to conduct heat 400 Conductivity 30 Fig. 19.4, Callister & Rethwisch Thermal (W/m-K) 10e. [Adapted from Metals Handbook: 0 Properties and Selection: Nonferrous alloys 20 and Pure Metals, Vol. 2, 9th ed., H. Baker, (Managing Editor), ASM 0 International, 1979, p. 315.] 100 0 0 10 20 30 40 Composition (wt% Zinc) Increasing impurity content (e.g., Zn in Cu) decreases thermal conductivity. Chapter 1 11  Thermal Properties (continued) Highly porous materials Material used for are poor conductors space shuttle of heat Ceramics Systems, Sunnyvale, CA Courtesy of Lockheed Aerospace Courtesy of Lockheed Missiles and Space Company, Inc. 100 μm Ceramic Fibers: Demonstration: – significant void – low thermal space conductivity of this – low thermal material conductivity Chapter 1 12  Magnetic Properties Magnetic Storage: Magnetic -- Recording medium is Permeability magnetized by vs. Composition: recording write head. -- Adding 3 atomic % Si makes Fe a better recording medium! Magnetizati Fe+3%Si Fe on Magnetic Field Adapted from C.R. Barrett, W.D. Nix, Fig. 20.23, Callister & Rethwisch 10e. and (Courtesy of HGST, a Western Digital A.S. Tetelman, The Principles of Company.) Engineering Materials, Fig. 1-7(a), p. 9, 1973. (Electronically reproduced by permission of Pearson Education, Inc., Upper Saddle River, New Jersey.) Chapter 1 13  Optical Properties The light transmittance of some materials depend on their structural characteristics: Aluminum oxide Aluminum oxide Aluminum oxide polycrystalline polycrystalline single crystal (high material (having material having degree of many small grains) some porosity—is perfection)—is —is optically optically opaque optically transparent translucent (Specimen preparation, P.A. Lessing) Chapter 1 14  Deteriorative Properties Small cracks formed in steel bar that was simultaneously stressed and immersed in sea water - Form of stress-corrosion cracking Cracks Fig. 17.21, Callister & Rethwisch 10e. (from Marine Corrosion, Causes, and Prevention, John Wiley and Sons, Inc., 1975.) Chapter 1 15  Deteriorative Properties (cont.) For stress-corrosion cracking, rate of crack growth is diminished by heat treating Adapted from Fig. 11.20(b), R.W. “as-received” Hertzberg, "Deformation and Fracture Mechanics of 10-8 Engineering Materials" (4th Crack Growth Rate ed.), p. 505, John Wiley and Sons, 1996. (Original source: “heat treated” Markus O. Speidel, Brown Boveri Co.) 10-10 (m/s) load For Aluminum alloy 7178 that is stressed while immersed in a saturated aqueous NaCl solution, crack growth rate is reduced by heat treating (160C for 1 h prior to Chapter 1 16 testing).  Example of Materials Selection: Artificial Hip Replacement Anatomy of a human hip joint and adjacent skeletal features Chapter 1 17  Materials: Artificial Hip Replacement (cont.) Hip joint problems can be painful and disabling Joint deterioration (loss of cartilage) as one ages Joint fracture arrows point to ends of fracture line X-ray of normal hip X-ray of fractured hip joint joint Chapter 1 18  Materials: Artificial Hip Replacement (cont.) Damaged and diseased hip joints can be replaced with artificial ones Materials requirements for artificial joints – Biocompatible – minimum rejection by surrounding body tissues – Chemically inert to body fluids – Mechanical strength to support forces generated – Good lubricity and high wear resistance between articulating surfaces Chapter 1 19  Materials: Artificial Hip Replacement (cont.) Hea Femoral stem — d (Ball inserted into top of hip ) bone (femur) Head (Ball) — affixed Liner & to femoral stem Shell Femor Shell — attached to al (Acetabular Stem ) pelvis Liner — into which Photograph courtesy of Zimmer, Inc., head fits Warsaw, IN, USA. Chapter 1 20  Materials: Artificial Hip Replacement (cont.) Materials used - Femoral stem — titanium or CoCrMo alloy - Head (Ball) — CoCrMo alloy or Al2O3 (ceramic) - Shell — titanium alloy - Liner — polyethylene (polymer) or Al2O3 (ceramic) Chapter 1 21  Materials: Artificial Hip Replacement (continued) Acetabular Hea shell and d liner (Ball ) Schematic diagram of X-ray of an an artificial hip implanted artificial hip Chapter 1 22  SUMMARY Appropriate materials and processing decisions require engineers to understand materials and their properties. Materials' properties depend on their structures; structures are determined by how materials are processed In terms of chemistry the three classifications of materials are metals, ceramics, and polymers Most properties of materials fall into the following six categories: mechanical, electrical, thermal, magnetic, optical, and deteriorative. An important role of engineers is that of materials selection. Chapter 1 23