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Engineering Materials Cheat Sheet (DRAFT) by

ENGINEERING MATERIALS

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Chapter 1 + 2:

CHAPTER 1:
Material Science:
Invest­igates the relati­onships that exist between Structure & Properties of materials.
Material Engine­ering:
Designing the structure of a material to produce required set of proper­ties.
Classi­fic­ation of materials:
Metals, Ceramics, Polymers & Composites
Advanced materials
Semico­ndu­ctors, Biomat­erials, Smart materials & Nano-m­ate­rials
CHAPTER 2:
Solid Materials Classi­fic­ations:
Crysta­lline Materials:
Atoms are situated in a repeat­ing­/pe­riodic array over large atomic distances.
Examples:
All metals, many ceramics, and some polymers
Lattice:
3D array of points coinciding with atom positions.
Unit Cells:
The basic structure unit or building block of the crystal structure
Metallic Crystal Struct­ures:
FCC: Face-C­entered Cubic
 
Atoms located at each corners and center of each face
 
Edge Length: a = 2R√2
 
Associ­ation: unit cell has four equivalent atoms (i.e. [1/8 x8]+[1/2 x6])
 
Co-ord­ination Number: Each atom has the same number of nearest- neighbor or touching atoms, FCC has 12
 
Atomic Packing Factor­(APF): APF = (volume of atoms in a unit cell)/ (volume of unit cell) FCC is 0.74
BCC: Body-C­entered Cubic
 
Cubic unit cell with atoms located at each corner and a single atom at the cube center.
 
Edge length: a = 4R/√3
 
Associ­ation #: 2 (1 atom from 8 corners + 1 single center atom)
 
Co-ord­ination #: 8
 
APF: 0.68
HCP: Hexagonal Closed­-Packed
 
Regular hexagons on top & bottom faces with one atom located at each corner (6 corners) and a single atom in the face center. Another plane provides 3 additional atoms is located between top and bottom faces.
 
Associ­ation #: 6 ( [12x1/6] + [2x1/2] + 3)
 
Co-ord­ination #: 12
 
APF: 0.74
Density Comput­ation:
p = (n x A) / (VC x NA)
 
p = Density
 
n = number of cells associated
 
A = Atomic weight
 
VC = Volume of unit cell
 
NA Avogadro's number (6.023x1023)
Volumes (VC):
 
FCC + BCC = a3
 
HCC = 6R2c√3
Crysta­lline and Noncry­sta­lline Materials
Single Crystals:
 
When the periodic and repeated arrang­ement of atoms is perfect or extends throughout the entirety of the specimen without interr­uption, the result is a single crystal.
Polycr­yst­alline:
 
Composed of a collection of many small crystals or grains; such materials are termed polycr­yst­alline.
Polymer Crysta­lli­nity:
 
Molecular substances of small molecules (as H2O, CH4,...) are totally Crysta­lline (as solid) or totally Amorphous (as liquids)
 
% crysta­llinity = [ρc (ρs – ρa)] / [ρs(ρc – ρa)]x100
Degree of crysta­llinity depends on:
 
Cooling rate during solidi­fic­ation
 
Chain config­uration
Noncry­sta­lline Solids:
 
Lacks of systematic and regular arrang­ement of atoms over relatively large atomic distances.
 
Amorphous : meaning literally without form (non-c­rys­talline structure)
 
Super-­cooled liquids : their atomic structure resembles that of liquids
 

CHAPTER 3 + 4

CHAPTER 3
Imperf­ections In Solids
Perfect order throughout crysta­lline materials on an atomic scale does not exist, all contain large numbers of various defects or imperf­ect­ions.
Crysta­lline defect:
Lattice irregu­larity in one/more of its dimensions on the scale of atomic diameter.
Classi­fic­ation of crysta­lline imperf­ect­ions:
Point defect:
 
associated with one/more atomic positions
Types:
Vacancy:
An atom is missing from one normally occupied site
 
Formed by: Solidi­fic­ation & Atomic Vibration
Equili­brium number of vacancies (Nv):
Nv = N x e(-Qv/kT)
 
N : Total number of atomic sites
 
Qv : Energy required for vacancy formation
 
T : Absolute Temper­ature
 
k : *Boltz­mann’s Constant (1.38x10-23 J/atom K or 8.62x10-5 ev/atom K)
Self-I­nte­rst­itial:
It means an atom is crowded into an inters­titial site
 
Linear defects:
 
It is 1D defect
Burgers Vector (BV):
Gives the magnitude & direction of lattice distortion associated with a disloc­ation.
Types:
Edge disloc­ation:
Linear crysta­l-line defect associated with the lattice distortion produced in the vicinity of the extra half-plane of atoms within a crystal.
 
BV : Perpen­dicular to the disloc­ation line.*
Screw disloc­ation:
A linear crysta­l-line defect associated with the lattice distortion produced when normally // planes are joined together to form a helical ramp.
 
BV : // to the disloc­ation line.
 
Interf­acial defect:
 
It is 2D defect.
Grain Bounda­ries:
It is the boundary separating two small grains­/cr­ystals having different crysta­llo­graphic orient­ation in polycr­yst­alline materials.
Grain Size determ­ina­tion:
N = 2n-1
 
N : Average number of grains per in2 at 100X magnif­ica­tion.
 
n : Grain size #
 
Compos­ition / Concen­tration
 
C1 = m1/ (m1+m2­)x100
 
nm1 = m1 x NA/A1
 
C1’ = nm1/ (nm1+n­m2)x100
 
ρ ave. = 100 / (C1/ρ1 + C2/ρ2)
 
A ave. = 100 / (C1/A1 + C2/A2)
 
CHAPTER 4
 

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