Concepts in Physical Metallurgy PDF

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This content has been downloaded from IOPscience. Please scroll down to see the full text. Download details: IP Address: 192.248.104.27 This content was downloaded on 21/07/2023 at 09:03 Please note that terms and conditions apply. You may also like: Semiclassical theory of resonant dissociative excitation of molecular ions by electron impact A A Narits, K S Kislov and V S Lebedev Global solvability and stabilization to a cancer invasion model with remodelling of ECM Chunhua Jin Spectroscopic and photometric studies of a candidate pulsating star in an eclipsing binary: V948 Her Filiz Kahraman Aliçavu 2nd International Conference on Rheology and Modeling of Materials (IC-RMM2)  IOP Concise Physics Concepts in Physical Metallurgy Concise lecture notes A Lavakumar Chapter 1 Introduction 1.1 The impact of materials on progress Humans have evolved through many metal ages. The progress that human civilizations have made can, in part, be attributed to their learning to use various kinds of metals. Thus metallurgy can be considered as an ancient form of technology that has made our way of life more sophisticated and developed. The beginning of the Industrial Revolution caused rapid growth in the production of iron and steel. Vast infrastructural developments took place due to improvements in metallurgy and materials science. It was thus at this time that metals and alloys, in particular steel, replaced wood as the principal structural material. The rapid developments in manufacturing, and the automotive and textile industries were also the result of the new large-scale steel production. On the eve of the twentieth century, we had copper, bronze, iron, steel, aluminum and rubber, in addition to wood, to use as structural materials. This paved the way for a series of inventions leading to a paradigm shift in road transport, from horse- drawn carriages to motorized vehicles. In the present day, innovations in materials technology have resulted in the development of light-weight alloys and composites. Automotive engine components have traditionally been made from ferrous alloys, but the emphasis on weight reduction for higher fuel efficiency has increased the use of aluminum for cylinder blocks, cylinder heads and other engine components. Some engine covers and intake manifolds are made of magnesium. Titanium is also used in the connecting rods of high-speed engines to reduce the reciprocating mass. The aviation and aerospace industry also owes much to developments in materials science. From the first Wright Flyer to the modern jets used today, the aerospace industry has made great progress in making human transportation much easier and faster. The use of light-weight and high-strength materials has made this possible. The aerospace industry today uses various light composite materials, such as carbon fiber composites, which are used in the bodies of various aircrafts. doi:10.1088/978-1-6817-4473-5ch1 1-1 ª Morgan & Claypool Publishers 2017  Concepts in Physical Metallurgy In the present era, electronic components have become an inseparable part of life. With advances in materials science, the sizes of computers and other instruments that use of electronic circuits have been reduced significantly. The development of smaller chips has brought the whole world to our palms. To illustrate the importance of materials science for the electronics industry, the example of the construction of various parts of a mobile phone can be given: Display. This relies upon the combination of a liquid crystal display and a touch screen for communication with the device. The touch screen is made from a conductive but transparent material, indium tin oxide, a ceramic conductor. Integrated circuits (ICs). At the heart of the iPhone are a number of ICs, built upon billions of individual transistors, all of which rely on precise control of the semiconductor material, silicon, to which dopant atoms have been added to change the silicon’s electronic properties Interconnects. The interconnects, which provide the links between components, are now made of copper, not aluminum, for higher speed and efficiency. Wireless. Microwave circuits need capacitors, which are ceramic insulators whose structure and composition is carefully controlled to optimize the capacitance. Battery. The battery is a modern Li-ion battery where the atomic structure of the electrodes is carefully controlled to enable the diffusion of the Li ions. Headphones. Most headphones use modern magnetic materials, whose structure and composition has been developed to produce very strong permanent magnets. This forms part of a transducer that turns electrical signals into sound. 1.2 A possible classification of physical metallurgy Figure 1.1 shows a broad classification of physical metallurgy. The ‘physical’ category will be the topic of this book, explaining the structure property correlation of the different classes of materials. Figure 1.1. A broad classification of physical metallurgy. 1-2  Concepts in Physical Metallurgy 1.3 Electrons to components In the early scientific literature, the atom was considered to be the smallest, chemically indivisible particle of matter. The smallest quantity of a substance which can exist freely by itself in a chemically recognizable form was known as a molecule. It was only in 1803 that John Dalton published his famous theory, the concept of atomicity. In this theory, he suggested that molecules are composed of atoms of different elements in a fixed proportion. In 1897, J J Thomson, while studying the passage of electricity through the low-pressure gases, discovered that gases ionize into positive and negative charges. Several studies, then showed the presence of various smaller particles known as fundamental particles. The fundamental particles inside the atoms that are important from the point of view of our subject are: Electrons. These are negatively charged particles. The mass of an electron is 9.1 × 10−31 kg, which is equal to 1/1836 of the mass of a hydrogen atom. Each possesses a unit negative charge of electricity, which is equal to 1.602 × 10−19 coulombs (C). Protons. These are positively charged particles. The mass of a proton is 1.672 × 10−27 kg. Each proton possesses a unit positive charge of electricity; this charge is also equal to 1.602 × 10−19 C. Neutrons. These are electrically neutral particles. The mass of a neutron is 1.675 × 10−27 kg. This is approximately equal to the mass of a proton. Each neutron is composed of one proton and one electron. As Richard Feynman said, ‘It would be very easy to make an analysis of any complicated chemical substance; all one would have to do would be to look at it and see where the atoms are …’. And by modifying those positions in different length scales, we can simply improve the properties of the materials. The possible length scale in this field is given below: 1. Electronic structure 2. Atomic structure 3. Crystal structure Table 1.1. Different classes of the properties of materials. Economic Price and availability, recyclability General physical Density Mechanical Modulus, yield and tensile strength, hardness, fracture strength, fatigue strength, creep strength, damping Thermal Thermal conductivity, specific heat Electric and magnetic Resistivity, dielectric constant, magnetic permeability Environmental interactions Oxidation, corrosion and wear Production Ease of manufacture, joining, finishing Aesthetic (appearance) Color, texture, feel 1-3  Concepts in Physical Metallurgy 4. Microstructure 5. Macrostructure 6. Component This leads to selecting a suitable material for a component by considering the various factors and properties (table 1.1). Further reading Askeland D R and Phulé P 2006 The Science and Engineering of Materials (Boston, MA: Cengage Learning) Avner S H 1997 Introduction to Physical Metallurgy (India: McGraw-Hill) Callister W D 2007 Callister's Materials Science and Engineering (Indian Adaptation, adapted by R Balasubramaniam) (New Delhi: Wiley) Raghavan V 2004 Materials Science and Engineering 5th edn (Englewood Cliffs, NJ: Prentice- Hall) Subramaniam A and Balani K (IITK) Materials Science and Engineering (e-book) MHRD, India 1-4