Structure of Metals 110

Transcription

1 Structure of Metals 110 Welcome to the Tooling University. This course is designed to be used in conjunction with the online version of this class. The online version can be found at We offer high quality web -based e -learning that focuses on today's industrial manufacturing training needs. We deliver superior training content over the Internet using text, photos, video, audio, and illustrations. Our courses contain "roll -up -your -sleeves" content that offers real -world solutions on subjects such as Metal Cutting, Workholding, Materials, and CNC with much more to follow. Today's businesses face the challenge of maintaining a trained workforce. Companies must locate apprenticeship programs, cover travel and lodging expenses, and disrupt operations to cover training needs. Our web -based training offers low -cost, all -access courses and services to maximize your training initiatives. Class Outline

2 Class Outline Objectives The Importance of Structure The Atom Valence Electrons The Periodic Table How Elements Interact Ionic and Covalent Bonds Metallic Bonds Molecular Bonding Crystal Formation in Metals Types of Crystal Structures Effects of Crystal Structure Crystal Growth Grains and Strength Summary Lesson:1/15 Objectives l Describe the importance of metal properties. l Identify the parts of the atom. l Describe a valence electron. l Describe the usefulness of the Periodic Table. l Explain why elements react with one another. l Distinguish between an ionic and covalent bond. l Define metallic bond. l Distinguish between primary and secondary bonds. l Describe how crystals form in metals. l Describe the different types of crystal structures. l Describe the significance of crystal structure. l Explain the beginning and end of crystal growth in metals. l Identify the impact of grain size. Figure 1. An illustration of a hydrogen atom. Figure 2. A representation of grains forming in a metal.

3 Lesson:1/15 Objectives l Describe the importance of metal properties. l Identify the parts of the atom. l Describe a valence electron. l Describe the usefulness of the Periodic Table. l Explain why elements react with one another. l Distinguish between an ionic and covalent bond. l Define metallic bond. l Distinguish between primary and secondary bonds. l Describe how crystals form in metals. l Describe the different types of crystal structures. l Describe the significance of crystal structure. l Explain the beginning and end of crystal growth in metals. l Identify the impact of grain size. Figure 1. An illustration of a hydrogen atom. Figure 2. A representation of grains forming in a metal. Lesson:2/15 The Importance of Structure The study of metals requires an understanding of their internal structure. In manufacturing, materials do not stay the same. They are transformed through chemical processes or physical processes. These processes can change the strength, hardness, and ductility of a metal. Plus, when you combine materials, the result is often a new material that shares some of the properties of the original materials. The structure of any material consists of the arrangement of its inner components. Structure can be studied at several levels: from the smallest particles that make up an atom illustrated in Figure 1, to structures that are visible to the human eye. The structure of a metal usually refers to the arrangement of atoms within the metal. Figure 2 illustrates a sample arrangement of atoms. The structure of metals affects your ability to control the behavior of a metal during the manufacturing Knowing metal's structure can help you pick the best metal for a Copyright 2015process. Tooling U, LLC. AllaRights Reserved. particular application under a certain pressure, temperature, or other condition.

4 Lesson:2/15 The Importance of Structure The study of metals requires an understanding of their internal structure. In manufacturing, materials do not stay the same. They are transformed through chemical processes or physical processes. These processes can change the strength, hardness, and ductility of a metal. Plus, when you combine materials, the result is often a new material that shares some of the properties of the original materials. The structure of any material consists of the arrangement of its inner components. Structure can be studied at several levels: from the smallest particles that make up an atom illustrated in Figure 1, to structures that are visible to the human eye. The structure of a metal usually refers to the arrangement of atoms within the metal. Figure 2 illustrates a sample arrangement of atoms. The structure of metals affects your ability to control the behavior of a metal during the manufacturing process. Knowing a metal's structure can help you pick the best metal for a particular application under a certain pressure, temperature, or other condition. Figure 1. An atom consists of incredibly small particles. Figure 2. Atoms are arranged in repeating patterns within a metal. Lesson:3/15 The Atom All materials are made up of atoms, which are the basic units of matter. The structure of an atom consists of a nucleus surrounded by electrons. As you can see in Figure 1, the nucleus is located in the center, and the electrons revolve around it. The path that an electron orbits around the nucleus is called a shell. Figure 2 shows an atom with three shells. The nucleus is the biggest part of the atom, and it is made up of positively charged protons and Copyright neutrons ToolingThe U, LLC. All Rights Reserved. uncharged number of protons in the nucleus determines the type of atom. For example, every oxygen atom contains eight protons. The electrons have a very small mass, nearly 2000 times smaller than the proton or neutron. The negative charge of electrons balances the

5 Lesson:3/15 The Atom All materials are made up of atoms, which are the basic units of matter. The structure of an atom consists of a nucleus surrounded by electrons. As you can see in Figure 1, the nucleus is located in the center, and the electrons revolve around it. The path that an electron orbits around the nucleus is called a shell. Figure 2 shows an atom with three shells. The nucleus is the biggest part of the atom, and it is made up of positively charged protons and uncharged neutrons. The number of protons in the nucleus determines the type of atom. For example, every oxygen atom contains eight protons. The electrons have a very small mass, nearly 2000 times smaller than the proton or neutron. The negative charge of electrons balances the positive charge of the protons. Normally, an atom contains the same number of electrons and protons to maintain this balanced charge. Figure 1. The nucleus is located in the center, and electrons orbit around the nucleus. Figure 2. An atom with three shells. Lesson:4/15 Valence Electrons Most atoms contain more than one shell. Like any sphere, the area of the outermost shell is larger than any shell closer to the nucleus. Therefore, the further you get from the center, the more room you have to put electrons in a layer. Every shell has a maximum number of electrons that it can contain. Figure 1 illustrates the shells of a sodium atom and shows how they are filled by electrons. The electrons that are located in the outer shell of an atom are called valence electrons. If an atom s outer shell is only partially filled, its valence electrons are easily borrowed or shared during reactions with other atoms. These electrons determine the many physical and chemical properties of materials.

6 Lesson:4/15 Valence Electrons Most atoms contain more than one shell. Like any sphere, the area of the outermost shell is larger than any shell closer to the nucleus. Therefore, the further you get from the center, the more room you have to put electrons in a layer. Every shell has a maximum number of electrons that it can contain. Figure 1 illustrates the shells of a sodium atom and shows how they are filled by electrons. The electrons that are located in the outer shell of an atom are called valence electrons. If an atom s outer shell is only partially filled, its valence electrons are easily borrowed or shared during reactions with other atoms. These electrons determine the many physical and chemical properties of materials. Figure 1. A sodium atom has one valence electron. Figure 2. A carbon atom has six valence electrons. Lesson:5/15 The Periodic Table There are just over 100 elements. As you can seen in Figure 1, these elements are arranged in a periodic table according to the number of protons they contain, from lowest to highest. The hydrogen atom in Figure 2 is at the top-left of the table because it contains only one proton. This arrangement creates seven horizontal rows called periods. The vertical columns, or groups of elements, have a similar number of electrons in the outer shell. This means they respond similarly to the same chemical and physical conditions. A working knowledge of the periodic table has its practical benefits. For instance, the arrangement of groups shows which element may be used to replace another element when making a metal

7 Lesson:5/15 The Periodic Table There are just over 100 elements. As you can seen in Figure 1, these elements are arranged in a periodic table according to the number of protons they contain, from lowest to highest. The hydrogen atom in Figure 2 is at the top-left of the table because it contains only one proton. This arrangement creates seven horizontal rows called periods. The vertical columns, or groups of elements, have a similar number of electrons in the outer shell. This means they respond similarly to the same chemical and physical conditions. A working knowledge of the periodic table has its practical benefits. For instance, the arrangement of groups shows which element may be used to replace another element when making a metal alloy, so that a similar material will result. For example, molybdenum (Mo) could be considered a substitute for chromium (Cr) because they both are in Group 6 of the table. Figure 1. The periodic table groups all the elements according to the number of protons contained in each atom. Figure 2. A hydrogen atom typically has one proton and one electron. Lesson:6/15 How Elements Interact The number of electrons in the outer shell determines how an atom interacts with other atoms. Every atom has the tendency to fill its outer shell to its maximum capacity. Other atoms with very few valence electrons in the outer shell are more willing to part with these electrons. For example, a hydrogen atom, which is shown in Figure 1, has only one electron in a single shell. Hydrogen atoms easily react with oxygen to form water since both of their outer shells are incomplete. The oxygen atom borrows two hydrogen electrons to fill its outer shell, as shown in Figure 3. Copyright 2015 Tooling that U, LLC. Rights Reserved. The number of protons theallatom contains identifies its atomic number. The atomic number is unique to each element. In other words, all atoms of the same element share the same number of protons.

8 Lesson:6/15 How Elements Interact The number of electrons in the outer shell determines how an atom interacts with other atoms. Every atom has the tendency to fill its outer shell to its maximum capacity. Other atoms with very few valence electrons in the outer shell are more willing to part with these electrons. For example, a hydrogen atom, which is shown in Figure 1, has only one electron in a single shell. Hydrogen atoms easily react with oxygen to form water since both of their outer shells are incomplete. The oxygen atom borrows two hydrogen electrons to fill its outer shell, as shown in Figure 3. The number of protons that the atom contains identifies its atomic number. The atomic number is unique to each element. In other words, all atoms of the same element share the same number of protons. Figure 1. A hydrogen atom has one electron orbiting in a single shell. Figure 2. An oxygen atom has six electrons orbiting in its outer shell. Figure 3. The oxygen atom borrows two atoms from hydrogen to fill its outer shell and form a water molecule.

9 Figure 3. The oxygen atom borrows two atoms from hydrogen to fill its outer shell and form a water molecule. Lesson:7/15 Ionic and Covalent Bonds Atoms combine with one another to form molecules. These atoms are held together by strong primary bonds, which depend on the actions of the atoms valence electrons. A water molecule consists of hydrogen and oxygen atoms. The way that the electrons interact in the molecule determines the type of primary bond. An ionic bond, which is depicted in Figure 1, is formed when an atom gives up a valence electron to help another atom fill its outer shell. Together, these two atoms bond together and form a molecule. Table salt is formed by ionic bonds. The covalent bond, shown in Figure 2, is formed when atoms share electrons in their outer shell. The shared electrons act as community electrons that complete the outer shells for both atoms simultaneously, like conjoined twins. Water is held together by covalent bonds. Figure 1. An ionic bond involves the borrowing of one or more electrons. Figure 2. A covalent bond involves the sharing of electrons. Lesson:8/15 Metallic Bonds Many atoms are held together by ionic and covalent bonds. However, a different type of primary bond holds the atoms of metals together. Metallic bonds consist of an electron cloud that allows for the movement of electrons from one atom to the next. Figure 1 illustrates the arrangement of electrons in a metallic bond. In a metallic bond, electrons are neither borrowed nor shared. Instead, electrons are free to roam. Because of this unique type of bond, most metals have a high electrical conductivity. For example, copper is a popular metal for making electrical wiring, which is shown in Figure 2. Copyright involves 2015 Tooling U, LLC. All Rights Reserved. Electricity the movement of electrons, and a metallic bond permits this movement.

10 Lesson:7/15 Ionic and Covalent Bonds Atoms combine with one another to form molecules. These atoms are held together by strong primary bonds, which depend on the actions of the atoms valence electrons. A water molecule consists of hydrogen and oxygen atoms. The way that the electrons interact in the molecule determines the type of primary bond. An ionic bond, which is depicted in Figure 1, is formed when an atom gives up a valence electron to help another atom fill its outer shell. Together, these two atoms bond together and form a molecule. Table salt is formed by ionic bonds. The covalent bond, shown in Figure 2, is formed when atoms share electrons in their outer shell. The shared electrons act as community electrons that complete the outer shells for both atoms simultaneously, like conjoined twins. Water is held together by covalent bonds. Figure 1. An ionic bond involves the borrowing of one or more electrons. Figure 2. A covalent bond involves the sharing of electrons. Lesson:8/15 Metallic Bonds Many atoms are held together by ionic and covalent bonds. However, a different type of primary bond holds the atoms of metals together. Metallic bonds consist of an electron cloud that allows for the movement of electrons from one atom to the next. Figure 1 illustrates the arrangement of electrons in a metallic bond. In a metallic bond, electrons are neither borrowed nor shared. Instead, electrons are free to roam. Because of this unique type of bond, most metals have a high electrical conductivity. For example, copper is a popular metal for making electrical wiring, which is shown in Figure 2. Electricity involves the movement of electrons, and a metallic bond permits this movement.

11 Lesson:8/15 Metallic Bonds Many atoms are held together by ionic and covalent bonds. However, a different type of primary bond holds the atoms of metals together. Metallic bonds consist of an electron cloud that allows for the movement of electrons from one atom to the next. Figure 1 illustrates the arrangement of electrons in a metallic bond. In a metallic bond, electrons are neither borrowed nor shared. Instead, electrons are free to roam. Because of this unique type of bond, most metals have a high electrical conductivity. For example, copper is a popular metal for making electrical wiring, which is shown in Figure 2. Electricity involves the movement of electrons, and a metallic bond permits this movement. Figure 1. A metallic bond creates an electron cloud where electrons move freely. Figure 2. Copper is used for electrical wire because it permits the flow of electrons. Lesson:9/15 Molecular Bonding Primary bonds hold atoms together. However, molecules are also attracted to each other with weaker bonds called secondary bonds. Figures 1 and 2 compare primary bonds and secondary bonds. Secondary bonds are not as powerful as the primary bonds that hold atoms together. Primary bonds are continuous; once an electron is borrowed or shared, another force is required to change that relationship. With secondary bonds, the forces that hold the molecules together are periodic and temporary. Secondary bonds are more likely to break apart than primary bonds. The composition of chewing gum helps to explain this distinction. Primary bonds are similar to the forces that hold the separate ingredients of gum together to determine its fundamental composition: sweeteners, flavors, and gum base. Secondary forces are similar to the forces that keep the gum from splitting into separate pieces.

12 Lesson:9/15 Molecular Bonding Primary bonds hold atoms together. However, molecules are also attracted to each other with weaker bonds called secondary bonds. Figures 1 and 2 compare primary bonds and secondary bonds. Secondary bonds are not as powerful as the primary bonds that hold atoms together. Primary bonds are continuous; once an electron is borrowed or shared, another force is required to change that relationship. With secondary bonds, the forces that hold the molecules together are periodic and temporary. Secondary bonds are more likely to break apart than primary bonds. The composition of chewing gum helps to explain this distinction. Primary bonds are similar to the forces that hold the separate ingredients of gum together to determine its fundamental composition: sweeteners, flavors, and gum base. Secondary forces are similar to the forces that keep the gum from splitting into separate pieces. Figure 1. Strong primary bonds occur between atoms. Figure 2. Weaker secondary bonds occur between molecules. Lesson:10/15 Crystal Formation in Metals When a metal is a solid, the atoms that make up the metal are tightly packed together. These atoms tend to arrange themselves into a predictable, repeating pattern, which is called the metal s crystal structure. Another name for this arrangement is space lattice system. The arrangement of atoms is always the same for a particular metal. The way that atoms arrange themselves is similar to how you would pack balloons into a box. Figure 1 shows atoms that are arranged in a crystal structure. Atoms arrange themselves in the crystal structure that requires the least amount of energy. In other words, the crystal structure of a metal is the most efficient way for the atoms to pack themselves in a given space.

13 Lesson:10/15 Crystal Formation in Metals When a metal is a solid, the atoms that make up the metal are tightly packed together. These atoms tend to arrange themselves into a predictable, repeating pattern, which is called the metal s crystal structure. Another name for this arrangement is space lattice system. The arrangement of atoms is always the same for a particular metal. The way that atoms arrange themselves is similar to how you would pack balloons into a box. Figure 1 shows atoms that are arranged in a crystal structure. Atoms arrange themselves in the crystal structure that requires the least amount of energy. In other words, the crystal structure of a metal is the most efficient way for the atoms to pack themselves in a given space. Figure 1. A crystal structure is a predictable, repeating pattern of atom arrangement. Lesson:11/15 Types of Crystal Structures Metals usually settle into one of three types of crystal structures: l l l The face-centered cubic (FCC) structure contains fourteen atoms. One atom is located at each corner, and another is located in the center of each face of the cube. Figure 1 shows an FCC structure. The body-centered cubic (BCC) structure contains nine atoms. One atom is located in the center, and the rest are located at each corner. Figure 2 shows a BCC structure. The hexagonal close-packed (HCP) structure contains seventeen atoms arranged in a hexagon. Seven atoms are arranged at each end, and three atoms are sandwiched in the middle. Figure 3 shows an HCP structure. Other crystal structures than these are possible. However, almost all metals consist of one of these three crystal structures. Figure 1. A face-centered cubic structure.

14 Lesson:11/15 Types of Crystal Structures Metals usually settle into one of three types of crystal structures: l l l The face-centered cubic (FCC) structure contains fourteen atoms. One atom is located at each corner, and another is located in the center of each face of the cube. Figure 1 shows an FCC structure. The body-centered cubic (BCC) structure contains nine atoms. One atom is located in the center, and the rest are located at each corner. Figure 2 shows a BCC structure. The hexagonal close-packed (HCP) structure contains seventeen atoms arranged in a hexagon. Seven atoms are arranged at each end, and three atoms are sandwiched in the middle. Figure 3 shows an HCP structure. Other crystal structures than these are possible. However, almost all metals consist of one of these three crystal structures. Figure 1. A face-centered cubic structure. Figure 2. A body-centered cubic structure. Figure 3. A hexagonal close -packed structure.

15 Lesson:12/15 Effects of Crystal Structure The crystal structure of a metal determines its properties. Because of the way they are packed together, metals with an HCP structure tend to be very brittle. FCC metals, illustrated in Figure 1, tend to be very ductile. It is easier for the atoms in an FCC structure to "slide around" than it is in an HCP structure. Some FCC metals include aluminum, copper, gold, lead, and nickel. These metals are typically soft, ductile, and not very strong. Common HCP metals are magnesium and titanium, and both metals are very brittle. Metals with a BCC structure, shown in Figure 2, share similar properties as well. These metals tend to be hard, and they are not always ductile. Iron, chromium, and tungsten are BCC metals at room temperature. The crystal structure of a metal can change at certain temperatures. Metals form a particular crystal structure because they use the structure requiring the least amount of energy at a particular temperature. However, energy can be changed by varying the temperature or pressure. For example, iron s BCC structure changes to FCC at higher temperatures. Figure 1. An FCC structure is common for ductile metals. Figure 2. A BCC structure is common for harder metals such as iron, chromium, and tungsten. Lesson:13/15 Crystal Growth Solid metals contain a particular crystal structure. However, when a metal is in its molten state, it has no crystal structure. Instead, the arrangement of the atoms is entirely random. As a liquid metal cools, small seed crystals form at the coolest positions, as shown in Figure 1. As the temperature continues to fall, these crystals grow by incorporating other atoms from the surrounding liquid. Copyright 2015 Tooling U, LLC. All Rights Reserved. These grains grow until they are stopped by the boundary of an adjoining neighbor, as shown in

16 Lesson:12/15 Effects of Crystal Structure The crystal structure of a metal determines its properties. Because of the way they are packed together, metals with an HCP structure tend to be very brittle. FCC metals, illustrated in Figure 1, tend to be very ductile. It is easier for the atoms in an FCC structure to "slide around" than it is in an HCP structure. Some FCC metals include aluminum, copper, gold, lead, and nickel. These metals are typically soft, ductile, and not very strong. Common HCP metals are magnesium and titanium, and both metals are very brittle. Metals with a BCC structure, shown in Figure 2, share similar properties as well. These metals tend to be hard, and they are not always ductile. Iron, chromium, and tungsten are BCC metals at room temperature. The crystal structure of a metal can change at certain temperatures. Metals form a particular crystal structure because they use the structure requiring the least amount of energy at a particular temperature. However, energy can be changed by varying the temperature or pressure. For example, iron s BCC structure changes to FCC at higher temperatures. Figure 1. An FCC structure is common for ductile metals. Figure 2. A BCC structure is common for harder metals such as iron, chromium, and tungsten. Lesson:13/15 Crystal Growth Solid metals contain a particular crystal structure. However, when a metal is in its molten state, it has no crystal structure. Instead, the arrangement of the atoms is entirely random. As a liquid metal cools, small seed crystals form at the coolest positions, as shown in Figure 1. As the temperature continues to fall, these crystals grow by incorporating other atoms from the surrounding liquid. These grains grow until they are stopped by the boundary of an adjoining neighbor, as shown in Figure 2. The rate of crystalline growth is called the nucleation rate. It is related to the time

17 Lesson:13/15 Crystal Growth Solid metals contain a particular crystal structure. However, when a metal is in its molten state, it has no crystal structure. Instead, the arrangement of the atoms is entirely random. As a liquid metal cools, small seed crystals form at the coolest positions, as shown in Figure 1. As the temperature continues to fall, these crystals grow by incorporating other atoms from the surrounding liquid. These grains grow until they are stopped by the boundary of an adjoining neighbor, as shown in Figure 2. The rate of crystalline growth is called the nucleation rate. It is related to the time passed and temperature loss. Figure 1. Initial seed crystals. Figure 2. Continued crystal growth. Lesson:14/15 Grains and Strength As the metal cools and solidifies to form crystals, grains develop in the metal, as shown in Figure 1. These grains usually grow more rapidly in one direction than in the other due to small temperature variations in the cooling metal. Grains near the surface of the metal branch out in a treelike fashion. This is called dendritic growth. The surfaces where grains contact their neighbors and stop growing are called grain boundaries, as shown in Figure 2. The grain size of a metal depends on the rate at which it was cooled and by the number of nucleation sites in the molten metal. Faster cooling often results in a stronger, tougher metal with smaller grains. Slower cooling results in a softer metal with larger grains that is easier to machine, but not as strong. Figure 1. Crystal growth develops as the liquid metal cools into a solid.

18 Lesson:14/15 Grains and Strength As the metal cools and solidifies to form crystals, grains develop in the metal, as shown in Figure 1. These grains usually grow more rapidly in one direction than in the other due to small temperature variations in the cooling metal. Grains near the surface of the metal branch out in a treelike fashion. This is called dendritic growth. The surfaces where grains contact their neighbors and stop growing are called grain boundaries, as shown in Figure 2. The grain size of a metal depends on the rate at which it was cooled and by the number of nucleation sites in the molten metal. Faster cooling often results in a stronger, tougher metal with smaller grains. Slower cooling results in a softer metal with larger grains that is easier to machine, but not as strong. Figure 1. Crystal growth develops as the liquid metal cools into a solid. Figure 2. Grain boundaries form as the various grains contact each other. Lesson:15/15 Summary The structure of a metal determines the properties of that metal. Knowledge of the structure of metals can help you choose the right metal for the job. All atoms contain electrons that circulate around a nucleus. The nucleus contains neutrons and protons. Valence electrons determine properties of an element as well as bonding arrangements. Each element is distinguished by its atomic number, which indicates the number of protons in its nucleus. Atoms are held together by ionic, covalent, or metallic bonds. Bonds typically form when an atom strives to fill its outer shell with electrons. A water molecule is an example of the covalent bond formed between one oxygen and two hydrogen atoms. The metals used in manufacturing generally form one of three crystal structures: face-centered cubic (FCC), body-centered cubic (BCC), and hexagonal close-packed (HCP) structures. FCC metals are soft and ductile, but not strong. BCC metals are hard but not ductile. HCP metals are brittle. As a liquid metal cools, crystals begin to form. These grains also influence the metals strength. A smaller grain structure is stronger than a larger grain structure. Figure 1. An atom consists of protons and neutrons in the nucleus, with electrons that

19 Lesson:15/15 Summary The structure of a metal determines the properties of that metal. Knowledge of the structure of metals can help you choose the right metal for the job. All atoms contain electrons that circulate around a nucleus. The nucleus contains neutrons and protons. Valence electrons determine properties of an element as well as bonding arrangements. Each element is distinguished by its atomic number, which indicates the number of protons in its nucleus. Atoms are held together by ionic, covalent, or metallic bonds. Bonds typically form when an atom strives to fill its outer shell with electrons. A water molecule is an example of the covalent bond formed between one oxygen and two hydrogen atoms. The metals used in manufacturing generally form one of three crystal structures: face-centered cubic (FCC), body-centered cubic (BCC), and hexagonal close-packed (HCP) structures. FCC metals are soft and ductile, but not strong. BCC metals are hard but not ductile. HCP metals are brittle. As a liquid metal cools, crystals begin to form. These grains also influence the metals strength. A smaller grain structure is stronger than a larger grain structure. Figure 1. An atom consists of protons and neutrons in the nucleus, with electrons that orbit around the nucleus. Figure 2. A water molecule holds hydrogen and oxygen atoms together by covalent bonds. Figure 3. A BCC crystal structure is common in harder metals.

20 Figure 3. A BCC crystal structure is common in harder metals. Class Vocabulary Term Definition Alloy A metal consisting of two or more materials. One of these materials must be a metal. Atom The smallest distinguishable unit of a material that maintains that material's characteristics. Atomic Number Body-Centered Cubic Brittle Chemical Processes Covalent Bond The number of protons that are contained within the nucleus of an element's atoms. The crystal structure that contains an atom in the center and one atom in each corner of a cube. A metal's unwillingness to be drawn, stretched, or formed. Brittle metals tend to break if subjected to these forces. A process that changes the atomic or molecular structure of the involved materials by altering the bonds that hold together their atoms and molecules. Chemical processes result in a new substance. A type of atomic bond that occurs when two atoms share electrons. Crystal Structure A repeating arrangement of the same type of atom that creates a uniform, repeating structure. Dendritic Growth Grain development that resembles the increasingly smaller branches of a tree. Ductility Electrical Conductivity Electron Electron Cloud Element Face-Centered Cubic Grain Group Hardness Hexagonal Close-Packed Ionic Bond A metal's ability to be drawn, stretched, or formed without breaking or cracking. A material's ability to act as a medium for conveying electricity. The smallest part of the atom that revolves around the nucleus. Electrons have a negative charge, and they are the basic charge of electricity. The arrangement of electrons within a metallic bond that permits the free movement of electrons from one atom to the next. One of the basic materials out of which all matter is made. Elements are the simplest of substances, and each element contains atoms with an identical number of protons. The crystal structure that contains one atom in the center of the six sides of a cube and one atom in each corner of the cube. A repeating arrangement of either the same type of atom or different atoms that create a uniform, repeating structure. A vertical column in the periodic table that contains elements with similar properties and chemical reactions. The ability of a material to resist penetration, indentation, or scratching. The crystal structure that contains a collection of atoms that are closely packed into the shape of a hexagon. Metals with a hexagonal close-packed crystal structure are very difficult to form. A type of atomic bond that occurs when one atom "borrows" one or more electrons from another atom. Mass The amount of matter that is contained within an object. Metal A hard, crystalline solid that conducts electricity and heat. It is shiny when polished, and it can be hammered, bent, formed, and machined. Metallic Bond A type of atomic bond that occurs when atoms "share" electrons that float about in a general electron cloud. Metals are held together by metallic bonds. Molecule TheRights smallest unit into which a material can be divided without changing its properties. A molecule consists of a Copyright 2015 Tooling U, LLC. All Reserved. group of atoms held together by strong primary bonds.

21 Class Vocabulary Term Definition Alloy A metal consisting of two or more materials. One of these materials must be a metal. Atom The smallest distinguishable unit of a material that maintains that material's characteristics. Atomic Number Body-Centered Cubic Brittle Chemical Processes Covalent Bond The number of protons that are contained within the nucleus of an element's atoms. The crystal structure that contains an atom in the center and one atom in each corner of a cube. A metal's unwillingness to be drawn, stretched, or formed. Brittle metals tend to break if subjected to these forces. A process that changes the atomic or molecular structure of the involved materials by altering the bonds that hold together their atoms and molecules. Chemical processes result in a new substance. A type of atomic bond that occurs when two atoms share electrons. Crystal Structure A repeating arrangement of the same type of atom that creates a uniform, repeating structure. Dendritic Growth Grain development that resembles the increasingly smaller branches of a tree. Ductility Electrical Conductivity Electron Electron Cloud Element Face-Centered Cubic Grain Group Hardness Hexagonal Close-Packed Ionic Bond A metal's ability to be drawn, stretched, or formed without breaking or cracking. A material's ability to act as a medium for conveying electricity. The smallest part of the atom that revolves around the nucleus. Electrons have a negative charge, and they are the basic charge of electricity. The arrangement of electrons within a metallic bond that permits the free movement of electrons from one atom to the next. One of the basic materials out of which all matter is made. Elements are the simplest of substances, and each element contains atoms with an identical number of protons. The crystal structure that contains one atom in the center of the six sides of a cube and one atom in each corner of the cube. A repeating arrangement of either the same type of atom or different atoms that create a uniform, repeating structure. A vertical column in the periodic table that contains elements with similar properties and chemical reactions. The ability of a material to resist penetration, indentation, or scratching. The crystal structure that contains a collection of atoms that are closely packed into the shape of a hexagon. Metals with a hexagonal close-packed crystal structure are very difficult to form. A type of atomic bond that occurs when one atom "borrows" one or more electrons from another atom. Mass The amount of matter that is contained within an object. Metal A hard, crystalline solid that conducts electricity and heat. It is shiny when polished, and it can be hammered, bent, formed, and machined. Metallic Bond Molecule A type of atomic bond that occurs when atoms "share" electrons that float about in a general electron cloud. Metals are held together by metallic bonds. The smallest unit into which a material can be divided without changing its properties. A molecule consists of a group of atoms held together by strong primary bonds. Neutron A particle with a neutral charge that is located in the nucleus of an atom. Nucleation Rate The rate at which small particles within a liquid metal begin to cool and form a solid.

22 group of atoms held together by strong primary bonds. Neutron Nucleation Rate Nucleation Site Nucleus Period Periodic Table Physical Processes Pressure Primary Bond Proton Secondary Bond Seed Crystal A particle with a neutral charge that is located in the nucleus of an atom. The rate at which small particles within a liquid metal begin to cool and form a solid. The locations at which seed crystals develop. The core of an atom around which electrons rotate. A horizontal row within the periodic table. The table containing all the elements arranged according to their atomic numbers. Vertical columns in the table contain elements with similar properties. A process that transforms metal by manufacturing processes including forming, machining, casting, and joining. A force or stress which, when applied, causes changes to the properties of the material. A bond that forms between atoms and that involves the exchanging or sharing of electrons. A particle with a positive charge that is located in the nucleus of an atom. A bond that involves attractions between molecules. Unlike primary bonding, there is no transfer or sharing of electrons. The origin of crystal growth that develops at one of the coolest points within a metal. Shell The approximately circular level in which electrons travel around the nucleus. Each shell consists of subshells, or orbitals. Space Lattice System The stacking of atoms into compact, symmetrical, three-dimensional arrangements that occurs as crystals form in a metal. Strength Temperature Valence Electron The ability of a material to resist forces that attempt to bend, stretch, or compress. The degree of heat within a material. An electron that is located in the outermost shell of an atom. Valence electrons are easily shared or transferred during a chemical reaction.