Metallurgical Engineering Exam 1 S&T (solved)

These materials exhibit both good strength and good ductility (formability) - ANSWER Metals These materials are generally hard and strong, but also brittle. - ANSWER Ceramics These materials offer good electrical a ...

These materials exhibit both good strength and good ductility (formability) - ANSWER Metals These materials are generally hard and strong, but also brittle. - ANSWER Ceramics These materials offer good electrical and thermal conductivity. - ANSWER Metals These materials typically have the lowest strength, but are light weight. - ANSWER polymers These materials can provide electrical and thermal insulation at high operating temperatures. - ANSWER Ceramics These materials would be the least suitable for use at elevated temperatures. - ANSWER Polymers In this type of bonding, the valence electrons are free to "wander" throughout the structure (high conductivity). - ANSWER Metallic This is the weakest of the four types of bonding. - ANSWER VanderWaals Two different types of atoms (an electron donor and an electron receiver) are required in this type of bonding. - ANSWER Ionic The bonds between carbon-carbon and carbon-hydrogen (common within polymers) are of this type. - ANSWER Covalent Materials bonded by this type of bond can exhibit both high strength and high ductility. - ANSWER Metallic The restricted number of "neighbors" leads to directional bonding and low densities in this type of bonding. - ANSWER Covalent When a magnesium atom gives u two electrons to an oxygen atom, resulting in the formation of MgO, the type of atomic bonding must be: - ANSWER Ionic In this type of bonding, the bonding is between molecules, not between atoms. - ANSWER VanderWaals A collection of ordered points in space is called a ___. - ANSWER Lattice The smallest volume of a lattice that retains all of its characteristics is called the: - ANSWER Unit Cell The number of immediately adjacent (i.e. touching) atoms to a given atom is called the: - ANSWER Coordination number The efficiency of filling available space (% occupied) can be evaluated by computing the: - ANSWER Packing factor In any lattice, corner atoms are shared by ___ unit cells. - ANSWER 8 The fraction of a corner atom that lies within a given unit cell is: - ANSWER 1/8 The number of atoms or lattice points fully-contained in a simple cubic unit cell is: - ANSWER 1 the coordination number for the simple cubic arrangement is: - ANSWER 6 The packing factor for the simple cubic structure is: - ANSWER .52 The number of atoms or lattice points fully contained in a BCC unit cell is: - ANSWER 2 In the BCC crystal structure, the coordination number is: - ANSWER 8 The packing factor for BCC crystal structure is: - ANSWER .68 In the BCC unit cell, the atoms are "touching" along the: - ANSWER Body diagonals Structures with stacked close-packed planes have ___ nearest neighbor atoms (i.e. the coordination number). - ANSWER 12 The stacking sequence for the FCC crystal structure is: - ANSWER ABCABC The number of atoms or lattice points fully-contained in the FCC unit cell is: - ANSWER 4 The packing factor (packing efficiency) of the FCC crystal structure is: - ANSWER .74 In the FCC unit cell, the atoms are "touching" along the: - ANSWER Face diagonals The stacking sequence for the HCP crystal structure is: - ANSWER ABABAB The packing factor (packing efficiency) of the HCP crystal structure is: - ANSWER .74 Aluminum, copper, silver and gold are "soft, weak and extremely ductile." These properties are characteristic of metals with crystal structure. - ANSWER FCC As a result of the ___ crystal structure, iron and steel at room temperature exhibit unusually high strength. - ANSWER BCC Magnesium and zinc die castings (such as Hot Wheels cars), are characteristically brittle. This is because these metals have the ___ crystal structure. - ANSWER HCP Materials that can exist in more than one crystal structure (depending upon the conditions of temperature and pressure) are called polymorphic (many-structured). Another term for this feature is: - ANSWER Allotropic When iron cools from red-heat to room temperature, it changes from FCC to BCC. Because of this change and the different packing factors associated with these structures, iron ___ during this change. - ANSWER Expands A mathematical description of directions and surfaces within a crystal is useful because: - ANSWER -Deformation occurs on particular planes in preferred directions -Certain properties may vary with direction -Atom arrangement varies with directions and along various surfaces Properties that assume different values when measured in different directions are: - ANSWER Anisotropic Lengths are measured in units of ___ crystallographic coordinate system: - ANSWER Lattice parameters