Materials Science

Question 1

Define material strength

Answer 1

The ability of a material to resist deformation

Question 2

Define Metallic Bond

Answer 2

Atoms do not share or exchange electrons. Instead, many electrons (roughly one for each atom) are free to move throughout the metal.

Question 3

Define edge dislocation

Answer 3

Consists of an extra row or plane of atoms in the crystal structure

Question 4

Define hardness

Answer 4

The property of a material that enables it to resist plastic deformation, penetration, indentation, and scratching

Question 5

What are the desirable properties of 304 stainless steel

Answer 5

• Extremely tough
• Corrosion resistant

Question 6

Define ductility

Answer 6

The ability of a material to deform easily on application of a tensile force

Question 7

Define screw dislocation

Answer 7

Develop by a tearing of the crystal parallel to the slip direction

Question 8

Define yield strength

Answer 8

The stress at which the material transitions from elastic to plastic deformation

Question 9

An imperfection that results from a missing atom in a lattice position is a _____________ defect

Answer 9

Vacancy defect

Question 10

Describe fatigue failure

Answer 10

A material’s tendency to fracture by means of progressive brittle cracking under repeated altering or cyclic stresses of an intensity considerably below the normal strength

Question 11

Describe annealing of a metal

Answer 11

A common heat treatment process that occurs slowly to an elevated temperature where it is held for a period of time and then cooled to relieve stress and improves ductility

Question 12

What characteristics are typical of alloys

Answer 12

• Stronger than pure metals
• Reduced electrical conductivity
• Reduced thermal conductivity

Question 13

Define Covalent Bond

Answer 13

Bond formed when two elements share electrons

Question 14

Describe heat treatment of a metal

Answer 14

The heating of a component to take advantage of metallic crystalline structures and their effects on the metal to gain desirable properties

Question 15

Name three types of point imperfections

Answer 15

• Vacancy defects
• Substitutional defects
• Interstitial defects

Question 16

Define Hydrogen Bond

Answer 16

Similar to a molecular bond but occurs due to the ease with which hydrogen atoms are willing to give up an electron to atoms of oxygen, fluorine, or nitrogen

Question 17

Eight atoms at the corners of a cube and one atom at the center of the cube describes a _____________ lattice-type structure

Answer 17

Body Centered Cubic (BCC)

Question 18

Define macroscopic material defects

Answer 18

• Defects that are three dimensional and on the macroscopic scale. Introduced to a material during refinement from its raw state or during fabrication.
• Most common bulk defects are called inclusions.

Question 19

Describe creep

Answer 19

The ability of a material to deform under constant stress or load

Question 20

Define mixed dislocation

Answer 20

Some combination of edge and screw dislocations

Question 21

Name three types of microscopic imperfections

Answer 21

• Point imperfection
• Line imperfection
• Interfacial imperfection

Question 22

An imperfection that results from an impurity, or a lattice atom, at an interstitial site

Answer 22

Interstitial defect

Question 23

Describe the relationship between grain size and tensile strength, ductility, and creep

Answer 23

• Smaller grain size increases tensile strength and ductility.
• Larger grain size improves high temperature creep properties.

Question 24

Body Centered Cubic (BCC) structures have what properties

Answer 24

• High Strength
• Low Ductility

Question 25

Hexagonal Close-Packed (HCP) structures have what properties

Answer 25

Not as ductile as FCC metals

Question 26

Describe work hardening

Answer 26

Occurs when straining a metal beyond the yield point to plastic deformation which causes the metal to become stronger and more difficult to form

Question 27

An imperfection that results from an impurity at a lattice position is a ________________ defect

Answer 27

Substitutional defect

Question 28

Define ultimate tensile strength

Answer 28

• The maximum resistance a material presents to fracture.
• The peak of the stress/strain curve

Question 29

A mixture of two or more materials, at leas one of which is a metal, is called a ____________

Answer 29

Alloy

Question 30

Describe cold working of a metal

Answer 30

Plastic deformation of a metal below the crystallization temperature which decreases ductility and increases strength by reducing the materials grain size without relieving the strain hardening

Question 31

Define Ionic Bond

Answer 31

One or more electrons is wholly transferred from an atom of one element to the atom of another element

Question 32

Describe hot working of a metal

Answer 32

Plastic deformation of a metal above the crystallization temperature which increases strength without reducing ductility since strain hardening is relieved

Question 33

Materials that are arranged in a pattern that periodically repeats in a three dimensional geometric lattice are said to be ______________ solids

Answer 33

Crystalline

Question 34

Eight atoms at the corners of a cube and one atom at the center of each of the faces of the cube describes a _____________ lattice-type structure

Answer 34

Face Centered Cubic (FCC)

Question 35

Describe quenching of a metal

Answer 35

The controlled cooling of a metal to take advantage of metallic crystalline structures and their effects on the metal to gain desirable properties

Question 36

Define malleability

Answer 36

The ability of a material to display large deformation when subjected to a compressive force

Question 37

Define Molecular Bond

Answer 37

When a temporary weak charge is created by electrons of neutral atoms spending more time in one region of their orbit than another, the molecule weakly attracts other molecules with similar weak charges.

Question 38

Define toughness

Answer 38

The work required to deform one cubic inch of metal until it fractures

Question 39

Materials that have no regular arrangement of atoms or molecules are said to be _____________ materials

Answer 39

Amorphous

Question 40

Face Centered Cubic (FCC) structures have what properties

Answer 40

• Lower strength than BCC
• Higher ductility than BCC

Question 41

Three layers of atoms with the top and bottom layers containing six atoms at the corners of a hexagon and one atom at the center of each hexagon and the middle layer containing three atoms nestled between the atoms of the top and bottom layers describes a ________________ lattice-type structure

Answer 41

Hexagonal Close-Packed (HCP)

Question 42

______________ imperfections can only occur in crystalline materials, can include edge, screw, and mixed types, and are also called dislocations

Answer 42

Line imperfection