KNJ 1433 Engineering Materials Week 1: Introduction to Materials Semester 1 2016/2017 1 Aims of the course • To provide students with the basic and relevant theory/knowledge, evaluation, analysis and application of the engineering materials. • This course includes introduction to materials, atomic structure and inter-atomic bonding, the structure of crystalline solids, phase equilibrium diagram, mechanical properties of engineering materials and their determination, deformation and dislocation, engineering applications of materials, properties and applications of Polymers, Ceramics and Composite Materials, degradation-corrosion and failure of 2 Materials. Course Outcomes By the end of this course, students should be able to: • Classify the types of materials and distinguish between their properties resulting from three various crystal structures in solids based on atomic packing, their microstructures, crystal defects and composition, strengthening mechanisms, failure mechanisms and degradation through chemical and electrochemical process such as corrosion. • Use the binary diagram in predicting the microstructure and composition of phase, and use the stress-strain curve to measure and predict the mechanical properties of the materials. • Design materials for Mechanical and Manufacturing applications through comparison of the mechanical & physical properties of Engineering materials. 3 Topics • • • • • • • • • • Introduction to Materials Atomic Structure and Inter-atomic Bonding The Structure of Crystalline Solids Phase Equilibrium Diagrams Mechanical Properties of Engineering Materials Reinforcement Mechanisms Corrosion of Metals Failure of Materials Engineering Ceramics Selection and Application of Materials 4 Assessment Test 1 & 2 20% Final Exam 50% Quiz/ Assignment 30% 5 References: 1. W. D. Callister, D. G. Rethwisch (2013). Materials Science and Engineering. 9th Edition, John Wiley and Sons, USA. 2. W. F. Smith, J. Hashemi (2010). Foundations of Materials Science and Engineering (SI Units). 5th Edition, McGraw Hill Publishers. 3. K. G. Budinski, M. K. Budinski (2009). Engineering Materials: Properties and Selection. 9th Edition, Pearson Education Series, USA 4. M. F. Ashby (2010). Materials Selection in Mechanical Design. 4th Edition, Butterworth Heinnemen, Elsevier, USA 6 Introduction to Engineering Materials • Materials Science and Materials Engineering Materials science Search for basic knowledge about: • internal structure • properties and • processing of materials Materials engineering Use of fundamental and applied knowledge of materials so that it can be utilised • products 7 Why study Engineering Materials? • Select right material among thousands of them for certain cases – mechanical properties, corrosion resistance, cost, etc. • Several criteria involved in selecting right materials such as: – In-service condition-dictate the properties required of the materials. – Any deterioration of materials properties that may occur during service operation. (e.g. : reduction of mechanical strength as a result from exposure to high temperature or corrosive environment). – Cost of finished product 8 Classification of materials • 6 main types: 1.Metals 2.Ceramics Fundamental class 3.Polymers 4.Composites 5.Electronic Process/application class 6.Biomaterial 7.Materials for future – smart material, nano 9 Classification of Materials 1. 2. 3. Metals: Materials in this group are composed of one or more metallic elements (e.g. iron, aluminium, copper, titanium, gold, and nickel), and often also non-metallic elements(e.g.. Carbon, nitrogen. and oxygen) in relatively small amounts. Ceramics: Ceramics are compounds between metallic and nonmetallic elements; they are most frequently oxides, nitrides and carbides. For example, common ceramic materials include aluminum oxide (or alumina, A1203), silicon dioxide (or silica, SiO2), silicon carbide (SiC), silicon nitride (Si3N3), and in addition, what some refer to as the traditional ceramics—those composed of clay minerals (i.e. porcelain), as well as cement and glass With regard to mechanical behaviour, ceramic materials are relatively stiff and strong— stiffness and strengths are comparable to those of the metals. Polymers: Polymers include the familiar plastic and rubber materials. Many of them are organic compounds that are chemically based on carbon, hydrogen, and other non metallic elements (i.e. O, N, and Si). Furthermore, they have very large molecular structures, often chainlike in nature, that often have a backbone of carbon atoms. E.g. PE, PVC, PP, PS, PC. 10 Classification of Materials 4. 5. Composites: Composed of two (or more) individual materials, which come from the categories previously discussed—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. A large number of composite types are represented by different combinations of metals, ceramics. and polymers. Furthermore, some naturally occurring materials are composites—for example, wood and bone. However, most of those we consider in our discussions are synthetic (or human-made)composites. (e.g. GFRP, CFRP etc.). Electronic (Semiconductors): have electrical properties that are intermediate between the electrical conductors (i.e., metals and metal alloys) and insulators (i.e., ceramics and polymers). Furthermore, the electrical characteristics of these materials are extremely sensitive to the presence of minute concentrations of impurity atoms, for which the concentrations may be controlled over very small spatial regions. Semiconductors have made possible the advent of integrated circuitry that has totally revolutionized the electronics and computer industries (not to mention our lives) over the past three decades. 11 Comparison of Properties Density Stiffness Strength Toughness 12 Classification of Materials 6. 7. Biomaterials: Biomaterials are employed in components implanted into the human body to replace diseased or damaged body parts. These materials must not produce toxic substances and must be compatible with body tissues (i.e., must not cause adverse biological reactions). All of the preceding materials— metals, ceramics, polymers, composites, and semiconductors—may be used as biomaterials. (i.e., artificial hip replacement) A) Smart Materials: Smart (or Intelligent) materials are a group of new and state-of-the-art materials now being developed that will have a significant influence on many of our technologies. The adjective smart implies that these materials are able to sense changes in their environment and then respond to these changes in predetermined manners—traits that are also found in living organisms. In addition, this smart concept is being extended to rather sophisticated systems that consist of both smart and traditional materials. (i.e., sensor – detect input signal actuator – performs a respond/adaptive function.) 13 Classification of Materials 7. B) Nanomaterials: Nanomaterials may be any one of the four basic types— metals, ceramics, polymers, and composites. They are not distinguished on the basis of their chemistry, but rather, size; the nano-prefix denotes that the dimensions of these structural entities are on the order of a nanometer (10-9 m) —as a rule, less than 100 nanometers (equivalent to approximately 500 atom diameters). Prior to the advent of nanomaterial, the general procedure scientists used to understand the chemistry and physics of materials was to begin by studying large and complex structures, and then to investigate the fundamental building blocks of these structures that are smaller and simpler. This approach is sometimes termed ‘top-down science. Electrical property 14 Processing/ Structure/ Properties/ Performance Correlations • Properties depend on structure ex: hardness vs structure of steel Hardness (BHN) (d) 600 500 400 (c) (a) (b) 4m 300 200 30m 30m 100 0.01 0.1 30m Data obtained from Figs. 10.21(a) and 10.23 with 4wt%C composition, and from Fig. 11.13 and associated discussion, Callister 6e. Micrographs adapted from (a) Fig. 10.10; (b) Fig. 9.27;(c) Fig. 10.24; and (d) Fig. 10.12, Callister 6e. 1 10 100 1000 Cooling Rate (C/s) • Processing can change structure ex: structure vs cooling rate of steel 15 The Materials Selection Process 1. Pick Application Determine required Properties Properties: mechanical, electrical, thermal, magnetic, optical, deteriorative. 2. Properties Identify candidate Material(s) Material: structure, composition. Electrical, Thermal, Magnetic, Optical 3. Material Identify required Processing Processing: changes structure and overall shape ex: casting, sintering, vapour deposition, doping forming, joining, annealing. 16 ELECTRICAL • Electrical Resistivity of Copper: Adapted from Fig. 18.8, Callister 6e. (Fig. 18.8 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.) • Adding “impurity” atoms to Cu increases resistivity. • Deforming Cu increases resistivity. 17 • Space Shuttle Tiles: THERMAL • Thermal Conductivity --Silica fiber insulation offers low heat conduction. Fig. 19.0, Callister 6e. (Courtesy of Lockheed Missiles and Space Company, Inc.) of Copper: --It decreases when you add zinc! 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. 19.4 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.) 18 • Magnetic Storage: MAGNETIC --Recording medium is magnetized by recording head. Fig. 20.18, Callister 6e. (Fig. 20.18 is from J.U. Lemke, MRS Bulletin, Vol. XV, No. 3, p. 31, 1990.) • 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. 19 • Transmittance: OPTICAL --Aluminum oxide may be transparent, translucent, or opaque depending on the material structure. single crystal polycrystal: low porosity polycrystal: high porosity Adapted from Fig. 1.2, Callister 6e. (Specimen preparation, P.A. Lessing; photo by J. Telford.) 20 DETERIORATIVE • Stress & Saltwater... --causes cracks! Adapted from Fig. 17.0, Callister 6e. (Fig. 17.0 is from Marine Corrosion, Causes, and Prevention, John Wiley and Sons, Inc., 1975.) • Heat treatment: slows crack speed in salt water! Adapted from Fig. 11.20(b), R.W. Hertzberg, "Deformation and Fracture Mechanics of Engineering Materials" (4th ed.), p. 505, John Wiley and Sons, 1996. (Original source: Markus O. Speidel, Brown Boveri Co.) --material: 4m 7150-T651 Al "alloy" (Zn,Cu,Mg,Zr) Adapted from Fig. 11.24, Callister 6e. (Fig. 11.24 provided courtesy of G.H. Narayanan and A.G. Miller, Boeing Commercial Airplane Company.) 21 Summary Materials Science and Engineering. • 6 different property classifications of materials that determine their applicability: mechanical, electrical, thermal, magnetic, optical, and deteriorative. • One aspect of materials science is the investigation of relationships that exist between the structures and properties of materials. • With regard to the design, production, and utilization of materials, there are 4 elements to consider— processing, structure, properties, and performance. • Three important criteria in materials selection are in-service conditions to which the material will be subjected, any deterioration of material properties during operation, and economics or cost of the fabricated piece. Classification of Materials. • On the basis of chemistry and atomic structure, materials are classified into three general categories: metals (metallic elements), ceramics (compounds between metallic and nonmetallic elements), and polymers (compounds composed of carbon, hydrogen, and other nonmetallic elements). In addition, composites are composed of at least two different material types. Advanced Materials. • Used in high-tech applications. These include semiconductors (having electrical conductivities intermediate between conductors and insulators), biomaterials (which must be compatible with body tissues), smart materials (those that sense and respond to changes in their environments in predetermined manners), and nanomaterials (those that have structural features on the order of a nanometer. some of which may be designed on the atomic/molecular level). 22