Chapter 1: Introduction to Materials Science and Engineering
Composition
The chemical make-up of a material.
Polycrystalline material
A material composed of many crystals (as opposed to a single-crystal material that has only one crystal).
Crystalline material
A material composed of one or many crystals. In each crystal, atoms or ions show a long-range periodic arrangement.
Smart material
A material that can sense and respond to an external stimulus such as change in temperature, application of a stress, or change in humidity or chemical environment.
Alloy
A metallic material that is obtained by chemical combinations of different elements (e.g., steel is made from iron and carbon). Typically, alloys have better mechanical properties than pure metals.
Glass
An amorphous material derived from the molten state, typically, but not always, based on silica.
Metal
An element that has metallic bonding and generally good ductility, strength, and electrical conductivity.
Materials engineering
An engineering oriented field that focuses on how to transform materials into a useful device or structure.
Single crystal
A crystalline material that is made of only one crystal (there are no grain boundaries).
Materials science
A field of science that emphasizes studies of relationships between the microstructure, synthesis and processing, and properties of materials.
Ceramics
A group of crystalline inorganic materials characterized by good strength, especially in compression, and high melting temperatures. Many ceramics have very good electrical and thermal insulation behavior.
Composites
A group of materials formed from mixtures of metals, ceramics, or polymers in such a manner that unusual combinations of properties are obtained (e.g., fiberglass).
Semiconductors
A group of materials having electrical conductivity between metals and typical ceramics (e.g., Si, GaAs).
Polymers
A group of materials normally obtained by joining organic molecules into giant molecular chains or networks. Polymers are characterized by low strengths, low melting temperatures, and poor electrical conductivity.
Glass-ceramics
A special class of materials obtained by forming a glass and then heat treating it to form small crystals.
Thermoplastics
A special group of polymers in which molecular chains are entangled but not interconnected. They can be easily melted and formed into useful shapes. Normally, these polymers have a chainlike structure (e.g., polyethylene).
Thermosets
A special group of polymers that decompose rather than melt upon heating. They are normally quite brittle due to a relatively rigid, three-dimensional network structure (e.g., polyurethane).
Materials science and engineering tetrahedron
A tetrahedron diagram showing how the performance-to-cost ratio of materials depends upon the composition, microstructure, synthesis, and processing.
Materials science and engineering (MSE)
An interdisciplinary field concerned with inventing new materials and improving previously known materials by developing a deeper understanding of the microstructure-composition-synthesis-processing relationships between different materials.
Physical properties
Characteristics such as color, elasticity, electrical or thermal conductivity, magnetism, and optical behavior that generally are not significantly influenced by forces acting on a material.
Grains
Crystals in a polycrystalline material.
Structure
Description of the arrangements of atoms or ions in a material. The structure of materials has a profound influence on many properties of materials, even if the overall composition does not change.
Processing
Different ways for shaping materials into useful components or changing their properties.
Fatigue failure
Failure of a material due to repeated loading and unloading.
Density
Mass per unit volume of a material, usually expressed in units of g/cm3 or lb/in.3
Plastics
Polymers containing other additives.
Mechanical properties
Properties of a material, such as strength, that describe how well a material withstands applied forces, including tensile or compressive forces, impact forces, cyclical or fatigue forces, or forces at high temperatures.
Grain boundaries
Regions between grains of a polycrystalline material.
Synthesis
The process by which materials are made from naturally occurring or other chemicals.
Polymerization
The process by which organic molecules are joined into giant molecules, or polymers.
Strength-to-weight ratio
The strength of a material divided by its density; materials with a high strength-to-weight ratio are strong but lightweight.
Microstructure
The structure of a material at the microscopic length scale.
