MATEPRO Module 4 Flashcards
In material selection, These materials were selected primarily because, not only did
they possess the desired properties and characteristics for
the intended functions of specific parts, but also they were
the ones that could be manufactured at the _________ cost
Lowest
With regards to the structures of materials, the ____________ and _____________ of a material all boil down to its ______________ and _____________.
Properties and performance, structure and processing
The number of protons in the nucleus
determines whether an atom will be
____________, ______________, or _______________
(low, high, intermediate)
Metallic, nonmetallic, or semimetallic.
Combination of multiple atoms
Molecules
Attractive Forces that hold the molecules together
Bonds
Examples of primary bonds are _________, ____________, _____________
Ionic bonds, Covalent Bonds, Metallic Bonds
Secondary bonds include _____________.
van de Waals forces
Occurs when one or more electrons from an outer orbit are transferred from one atom to another.
Ionic bonds
Ionic bonds generally have ____________ and ________________.
Poor ductility and low thermal/electrical conductivity.
The electrons in outer orbits are shared by atoms to form molecules. Atoms achieve stability by sharing electrons with other atoms
Covalent Bonds
Covalent bonds generally have ____________, ____________, and ________________.
Low electrical conductivity and high hardness, and high melting point.
Occurs in atoms with very few valence electrons (1-3)
Metallic bonds
Metallic bonds generally have ____________ and ________________.
High thermal and electrical conductivity.
Occurs when a molecule is polarized: one side is more positive/negative than the other. The attraction of opposite charges without electron transfer
Van der Waals forces
The various orderly configurations of the atoms when metals solidify from a molten state
Crystals
Refers to the atomic arrangement when solidified
Crystal Structure
The smallest group of atoms showing the characteristic
lattice structure of a particular metal. It is the building block of
crystal.
Unit Cell
Topologically ordered, three-dimensional geometrical array of atoms composed of one or more repeating unit cells
Lattice Structure
Lacks the periodically ordered arrangement
that is characteristic of a crystalline solid
Amorphous Structure
When metals solidify, the atoms assume a _______________.
Crystal Structure
A metal is normally made up of only____-______ or ______________
structure, but some can have multiple. These are called _____________ or ____________.
One crystal structure or lattice structure, allotropic or polymorphic
For the crystal structure of metals, three basic atomic arrangements include the following (mention their characteristic)
- Body-centered cubic (BCC); high strength
- Face-centered cubic (FCC) ; high ductility
- Hexagonal Close Packed (HCP); Brittle
The change of a metal’s
lattice structure from one form to another
Allotropic transformation
The top and bottom planes in the HCP structure
Basal Planes
The modification of any of the three arrangements
by adding atoms of some other metals
Alloying
Rank the three crystal structures of metal based on packed configurations (from most to least packed)
- HCP
- FCC
- BCC
When the crystal is subjected to an external force, it returns to its original shape when force is removed
Elastic deformation
Also known as permanent deformation. If the force on the crystal structure is increased sufficiently that it does
not return to its original shape when the force is removed
Plastic deformation
Ratio of the applied shearing force
to the cross-sectional area being sheared
Shear stress
Properties that are uniform in all directions
Isotropic properties
Properties that vary with direction
Anisotropic properties
The combination of a slip plane and
its direction
Slip System
Metals with 5 or more slip systems are __________.
Ductile
List the number of slip systems per crystal (BCC, FCC, HCP)
BCC - 48 possible slip systems
FCC - 12 slip systems
HCP - 3 slip systems
The strength of metals can be theoretically calculated
using ____________.
Molecular dynamics
The ___________ strength of metals is found to be approximately one to two orders of magnitude __________ than the strength levels obtained from molecular
dynamics.
Actual, lower
The reason for the discrepancy between the actual strength and theoretical calculation.
Defects and imperfections in the crystal structure
When the material is raised to a high
enough temperature, the material will
attempt to _____________ to release some of that energy
Recrystallize
The greater the amount of deformation, the ________ the recrystallization temperature
Lower
When metals are plastically
deformed at temperatures below
their recrystallization temperature,
the process is called _____________ .
Cold Working
If a material is deformed at
a temperature greater than
its recrystallization
temperature, the process is
called ____________.
Hot Working
Materials composed of two or more different
elements, which tend to exhibit their own characteristic
properties
Alloys
Consists of either a single crystal (for
pure metals) or polycrystalline aggregate (for alloys)
Grain / crystalline structure
The initial stage of crystal formation
Nucleation
The surfaces
that separate the individual
grains once they interfere with
and impinge upon one another
Grain boundaries
The behavior of a single crystal or
a single grain is __________ .
Anisotropic
