Material Science and Engineering PDF

Material Science and Engineering Early civilizations have been designated by the level of their materials development: 1. Stone Age – limited number of materials, those that occur naturally: stone, wood, clay, skins and so on – approximately 2.5 million BC Early civilizations have been designated...

Material Science and Engineering Early civilizations have been designated by the level of their materials development: 1. Stone Age – limited number of materials, those that occur naturally: stone, wood, clay, skins and so on – approximately 2.5 million BC Early civilizations have been designated by the level of their materials development: 2. Bronze Age – techniques were discover for producing materials that had properties superior to those on the natural one: pottery and various metals – approximately 3500 BC Early civilizations have been designated by the level of their materials development: 3. Iron Age – it was discovered that the properties of a material could be altered by heat treatments and by the addition of other substances. At this point, materials utilization was totally a selection process that involved deciding from a given, rather limited set of materials the one best suited for an application by virtue of its characteristics: metal alloys – approximately 1000 BC Different material that evolved (after 100 years) with rather specialized characteristics that meet the needs of our modern and complex society: Metals Plastics Glasses Fibers MATERIALS SCIENCE AND ENGINEERING Materials science ✓ involves investigating the relationships that exist between the structures and properties of materials. Materials scientists ✓ develop or synthesize new materials. MATERIALS SCIENCE AND ENGINEERING Materials engineering ✓ on the basis of these structure – property correlations, designing or engineering the structure of a material to produce a predetermined set of properties. Materials engineer ✓ create new products or systems using existing materials, and/or develop techniques for processing materials. MATERIALS SCIENCE AND ENGINEERING  Structure of a material usually relates to the arrangement of its internal components ▪ Microscopic – subject to direct observation using some type of microscope. ▪ Macroscopic – structural elements that may be viewed with the naked eye. MATERIALS SCIENCE AND ENGINEERING Property ✓ is a material trait in terms of the kind and magnitude of response to a specified imposed stimulus.  Generally, definitions of properties are made independent of material shape and size. Different categories of all important properties of solid material:  Mechanical – relate deformation to an applied load or force: examples include elastic modulus and strength.  Electrical – includes conductivity and dielectric constant, the stimulus is an electric field.  Thermal – behavior of solids can be represented in terms of heat capacity and thermal conductivity. Different categories of all important properties of solid material:  Magnetic – demonstrate the response of a material to the application of a magnetic field.  Optical – the stimulus is electromagnetic or light radiation; index of refraction and reflectivity are representative optical properties.  Deteriorative – relate to the chemical reactivity of materials.  The four components of the discipline of materials science and engineering and their interrelationship PROCESSING STRUCTURE PROPERTIES PERFORMANCE o The structure of a material will depend on how it is processed; furthermore, a material’s performance will be a function of its properties. WHY STUDY MATERIALS SCIENCE AND ENGINEERING? 1. Select the right material from the many thousands that are available. (ex. Strength and ductility) 2. Deterioration of material properties that may occur during service operation (ex. Temperature or corrosive environment) 3. Economics (ex. Expense incurred during fabrication to produce desired shape) PROPERTIES OF MATERIALS 1. Strength - The ability of a material to stand up to forces being applied without it bending, breaking, shattering or deforming in any way. PROPERTIES OF MATERIALS 2. Elasticity - The ability of a material to absorb force and flex in different directions, returning to its original position. PROPERTIES OF MATERIALS 3. Plasticity - The ability of a material to be change in shape permanently. PROPERTIES OF MATERIALS 4. Ductility - The ability of a material to change shape (deform) usually by stretching along its length. PROPERTIES OF MATERIALS 5. Tensile Strength - The ability of a material to stretch without breaking or snapping. PROPERTIES OF MATERIALS 6. Malleability - The ability of a material to be reshaped in all directions without cracking. PROPERTIES OF MATERIALS 7. Toughness - A characteristic of a material that does not break or shatter when receiving a blow or under a sudden shock. PROPERTIES OF MATERIALS 8. Hardness - The ability of a material to resist scratching, wear and tear and indentation. PROPERTIES OF MATERIALS 9. Conductivity - The ability of a material to conduct electricity. PROPERTIES OF MATERIALS 10. Young’s Modulus and Specific Stiffness - Young's modulus measures the resistance of a material to elastic (recoverable) deformation under load. PROPERTIES OF MATERIALS 11. Elongation - Elongation to failure is a measure of the ductility of a materials, in other words it is the amount of strain it can experience before failure in tensile testing. PROPERTIES OF MATERIALS 12. Density - Density is a measure of how heavy an object is for a given size, i.e. the mass of material per unit volume. PROPERTIES OF MATERIALS 13. Maximum Service Temperature - The strength of a material tends to fall quickly when a certain temperature is reached. PROPERTIES OF MATERIALS 14. Cost - Materials are usually sold by weight or by size. Material costs are therefore given as cost per unit weight or cost per unit volume. PROPERTIES OF MATERIALS 15. Energy Content - Energy is used to mine, refine and process materials - this is called the "energy content" of the material. Energy content is closely related to recycling. PROPERTIES OF MATERIALS 16. Recycle Fraction - The fraction recycled is a measure of the proportion of a material in use in products which can economically be recycled. PROPERTIES OF MATERIALS 17. Resistivity - Resistivity is a measure of the resistance to electrical conduction for a given size of material.  Classification of materials This scheme is based primarily on chemical makeup and atomic structure. 1. METALS  Materials in this group are composed of one or more metallic elements (such as iron, aluminum, copper, titanium, gold, and nickel), and often also nonmetallic elements (for example, carbon, nitrogen, and oxygen) in relatively small amounts.  - The term metal alloy is used in reference to a metallic substance that is composed of two or more elements. Characteristics : ▪ Stiff and Strong ▪ Ductile ▪ Resistant to Fracture ▪ extremely good conductors of electricity and heat ▪ not transparent to visible light ▪ a polished metal surface has a lustrous appearance 2. CERAMICS  compounds between metallic and nonmetallic elements; they are most frequently oxides, nitrides, and carbides  traditional ceramics—those composed of clay minerals (i.e., porcelain), as well as cement, and glass Characteristics : ▪ Stiff and Strong ▪ Very hard ▪ extremely brittle (lack ductility) ▪ highly susceptible to fracture ▪ typically insulative to the passage of heat and electricity ▪ more resistant to high temperatures and harsh environments than metals and polymers ▪ optical characteristics, ceramics may be transparent, translucent, or opaque 3. POLYMERS  Many of them are organic compounds that are chemically based on carbon, hydrogen, and other nonmetallic elements  they have very large molecular structures, often chain-like in nature that have a backbone of carbon atoms Characteristics: ▪ not as stiff nor as strong as these other material types ▪ extremely ductile and pliable (i.e., plastic), which means they are easily formed into complex shapes. ▪ relatively inert chemically and unreactive in a large number of environments. ▪ tendency to soften and/or decompose at modest temperatures ▪ low electrical conductivities and are nonmagnetic. 4. COMPOSITES  Composed of two (or more) individual materials, which came from 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 to incorporate the best characteristics of each of the component materials.  Ex. Fiberglass , carbon fiber-reinforce polymer (used in aircraft and high- tech sporting equipment) 5. ADVANCE MATERIALS  Materials that are utilized in high-technology (or high-tech) applications  Semiconductors, biomaterials, and what we may term “materials of the future” (that is, smart materials and nanoengineered materials).  Used for lasers, IC, LCD and fiber optics. Classification Of Advance Materials a. Semiconductors – have electrical properties that are intermediate between the electrical conductors and insulators. Classification Of Advance Materials b. Biomaterials – are employed in components implanted into the human body for replacement if diseased or damaged body parts. Classification Of Advance Materials c. Materials of the future i. Smart materials ✓ Able to sense changes in their environments and respond to these changes in predetermined manners –traits that are also found in living organisms. ✓ Components : sensor (detects and input signal) and actuator ( performs a responsive and adaptive function). ✓ Sensor materials include optical fibers, piezoelectric materials, and microelectromechanical devices. ✓ Actuator materials include shape memory alloys, piezoelectric ceramics, magnetorestrictive materials and electrorheological/magnetorheological fluids. Classification Of Advance Materials ii. Materials of the future  Nanoengineered materials  Nanotechnology is the study of properties of materials whose dimensions are on the order of a nanometer (10^-9 m) – as a rule, less than 100 nanometers.