EA = −Ar,EB =

Brn,EN = −

Ar+Brn, r0 = (

AnB)1/(1−n)

%IC = (1− exp(−0.25)(XA − XB )2 )*100,

   

ρ =nAVcNA

,ρmetal > ρceramics >polymers  

u = 13(2u' − v' ),v = 1

3(2v' −u' ), t = −(u+ v),w = w'

i = −(h+ k)  

0D:Vaccumcis,Intrstituals,Impritice 3D:Pore or crack

1D:Screw or edge dislocation 2D:Grain boundaries

NV = N exp−QV

kTD = D0 exp(−

Qd

RT) ∂C∂t

= D ∂2C∂x2

 

 

σ =FA0

= Eε,ε = Δll0,%EL = (

l f − l0l0

)*100,Toughness :σ T = KεnT

%RA = (A0 − Af

A0)*100,Re silience :Ur =

12σ yεy (y→ yield)

Grain_ size_ reduction :σ yield =σ 0 + kyd−1/2

Solid _ Solution :σ y ~ C1/2 (C = concentration)

%CW =πr20 −πr

2d

πr20*100

 

)%2.91()%8()%9.71(:,:

:)%2.91()%8()%9.71(:

),()()(C:_

,)exp(:

_,_,_,)(1,

__,__,__mod:,]2[:

3

02

2max

max

2/1

AgwtAgwtAgwtLEgLPeritectic

CFeEutectoidAgwtAgwtAgwtLEg

CCLreactionEutectictll

tRTQ

KsCreep

SamplitudestressrangestressstressmeanYK

aaYK

crackoflengthaenergysurfacespecificelasticityofulusEaE

Crack

EEE

s

Cn

armdesign

CCdesign

ss

C

βα

γδ

αγ

βα

βα

εσ

σσσσππ

σ

γπγ

σ

βα

ε

+⎯→←

⎯→←+

+⎯→←

+⎯→←

+⎯→←

Δ

Δ

=Δ

Δ=−=

====<<

===

•

 

     

BCC   FCC  

2   4  

a=4R/(√3)   a=2R√2  

0.68   0.74  

8   12  

Cubic a=b=c α=β=ϒ=90°

Hexagonal a=b≠c α=β=90°, ϒ=120°

Tetragonal a=b≠c α=β=ϒ=90°

Trigonal a=b=c α=β=ϒ≠90°

Orthorhombic a≠b≠c α=β=ϒ=90°

Monoclinic a≠b≠c α=ϒ=90°≠β

Triclinc a≠b≠c α≠β≠ϒ≠90°

   Eutectic:Liquid-­‐>two  solid  phases  Eutectoid:One  solid  phase-­‐>two  other  solid  phase  Peritectic:Liquid&one  solid  phase-­‐>a  second  solid  In  Fe-­‐C  diagram:    wt%C  <0.76:  Hypoeutectoid  steel,ferrite-­‐soft  most  0.76<wt%C<2.1  :  Hypereutectoid  steel,  Fe3C  most  Polymer:  Saturated  hydrocarbons:1  C-­‐  4  other  atoms  Methane:CH4,  Ethane:C2H6,  Propane:C3H8,  Butane:C4H10,  Pentane:C5H12,  Hexane:C6H14  Doubel  bond:1  C-­‐3  other  atoms;  Triple  bond...  

 Isomerism:   Same   chemical   formula,   different   structure.   Condensation:  Process   is   conducted   in  presence  of   a   catalyst.  Water,CO2  are   commonly  condensed  out.  

       

   R(cation)/R(anion):   less   than   0.155,  

linear;  0.155-­‐0.225,  triangular;  0.225-­‐0.414,  TD;  0.414-­‐0.732,  OH;  0.732-­‐1.0,  Cubic;  Zinc  Blende:  TD  site  AX(include  rock-­‐salt),AX2,ABX3.  FCC:4OH  sites,  8TD  sites  Linear:  Repeating  Units:  single  chains,  Van  der  waals  force,  very  flexible,  example:  Nylon.  Branched:  Side  chains,  lowers  density  due  to  chain  packing,  example:LDPE  Cross-­‐Linked:  Covalent  bonding,  stronger,  can  be  caused  by  a  non-­‐reversible  reaction.  Some  rubber:  adding  in  additional  additives  (Vulcanization).    Network:  Multifunctional   (3   or  more   activate   covalent   bond).   Example:   epoxy   –   good  mechanical   strength   and   thermal  properties.    Conformation:Molecular  orientation  can  be  changed  without  break  bonds.  Configurations  –   to  change  must  break  bonds  Stereoisomerism:  mirror  plane;  Tacticity:   isotactic:   all   R   groups  on   same   side;   syndiotactic:   all   R   groups   alternate   side;  atactic:  random  R  groups.  Cis  isomerism:  bulky(CH2)  groups  on  same  side.  Trans  isomerism:  bulky  group  on  opposite  side.  Copolymers:  random;alternating(ABAB);block(AAAABBBB);graft(branch).  Drawing  increase  in  %Crystallinity,  increase  in  TS  and  E,  decrease  in  ductility.  Annealing  reverses  effects  of  drawing.  Thermoplastics:  Little  cross-­‐linking;  ductile;  soften  with  heat.  Eg:  PE,PS.  Thermosets:  Cross-­‐liking(15-­‐50%);brittle;don’t  soften  with  heat,Eg:Epoxy.  Improve  mechanical  properties:  Fillers:  Improve  TS  and  toughness,  reduce  cost;  Plasticizers:  Reduce  Tg,  less  brittle.  Processing:  Thermoplastic:  can  be  reversibly  cooled  &  reheated;  heat  till  soft,  shape  as  desired,  then  cool.  Thermoset:when  heated  forms  a  network,  degrades  when  heated,  mold  the  prepolymer  then  allow  further  reaction.  Polymer  types:  Elastomers(rubber);Fibers;Coatings;Adhesives;Films;Foams.  Ceramics:  Applications:  Die  blanks;  die  surface;  tools(Singal  crystal  or  add  polycrystalline  diamond);  sensors.  Fabrication:  Glass  forming(Pressing,  blowing,  fiber  drawing,  sheet  forming),  Particulate  forming(Slip  casting,  hydroplastic  forming,   drying,   firing,   sintering,uniaxial   compression,   hot   pressing),   Cementation.   Application:   Heat   engine;   ceramic  armor.     Heat   treating  Glass:   Annealing:   remove   internal   stress   caused   by   uneven   cooling;   Tempering:   put   surface   part  into  compression  to  suppresses  growth  of  crack  from  surface  scratches.  For  glass:  viscosity  decrease  with  T  increase  while  specific  volume  increase  with  T;  impurities  lower  deformation  temperature.  Defect:  Frenkel  Defect:   a   cation   is  out  of  place.Shottky  Defect:   a  paired  set  of   cation  and  anion  vacancies.   Substitutional  cation  impurity:  cation  vacancy;  Substitutional  anion  impurity:  anion  vacancy.  Metal  Ferrous  alloy  with  >2.1  wt%  C,  low  melting.  Cementite  decomposes  to  ferrite  +  graphite.  Limitations  of  ferrous  alloy:  relatively  high  density,  low  conductivity,  poor  corrosion  resistance.  Cu  Alloy:  Brass;Bronze;Cn-­‐Be  Alloy:  density=2.7g/cm3;Mg  Alloy:  density  =1.7g/cm3,ez  ignite;Refractory  metal:  Hight  melt  T,eg:Nb,Mo;  Noble  metal:  oscide  corrosion  resistance;  Ti  alloy:  density=4.5g/cm3,reactive  at  high  T.  Strengthen  and  Failure  %EL<5% -- Brittle(Ceramic) %EL>5% Not Brittle (Metal)

Resilience: Capacity to absorb energy when deformed elastically and then upon loading, to have this energy recovered.

Toughness: Ability to absorb energy up to fracture. Hardness: Resistance to permanently indenting the surface.

Moch Hardness; Rockweel Hardness; Brinell Hardness; K&V Microindetantion

Youngs’Modulus: Metal≈Ceramics>Polymers; Yield Strength Metal> Polymers Tensile strength:

Metal≈Ceramics≈Polymers

If dislocation does not occur,neiter does deformation. Smaller grain/crystal size more likely to slip. Larger crystal yield at first.

Strengthening 1: Reduce grain size. Grain boundaries are barriers to slip and strength increases with misorientation. Before

rolling: isotropic; uniformity in all direction. After: anisotropic, direction dependence Strengthening 2: Solid solutions. Impurity atoms distort the lattice and generate stress oppose dislocation direction. Strengthening 3: Precipitation Strengthening. Hard

precipitates are difficult to shear. Strengthening 4: Cold working: Forging, Drawing, Rolling, Extrusion. Room temperature,

reversible.

Recovery: No change in strength & ductility

Recrystallization: New crystals are formed

Grain growth: Grain boundary area increase => energy is reduced.

Ductile fracture: occurs with plastic deformation, warning before failure

Brittle fracture: occurs with little or no plastic deformation, no warning

Brittle failure: Many pieces, little deformation

Ductile failure: One piece, large deformation

Intergranular: between grains; Intragranular: within grains. Three non-destructively ways to detect: 1)X-ray 2)Ultrasonic

inspection 3)Surface inspection(Dye penetration) Ts(Engineering material)<Ts(Ideal or perfect material)

Longer sample, smaller load for failure. Flaws cause premature failure, larger samples contain more flaws.

Increased loading rate increases . .y sand Tσ ,decreases %EL.

Improving fracture toughness: a)add monoclinic grain to crack b).Microcracks. Fatigue = failure under cyclic stress.

Fatigue can cause part failure below critical stress. Improving fatigue lifeL impose a compressive surface stress; remove stress

concentrators. Water and some chemicals can accelerate crack growth and shorten life performance(Break network).

Metal   fabrication   methods:   Forming(Forging,   rolling,   drawing,   extrusion),Casting(die,sand,investment),Joining(Powder  metallurgy,  welding)  How  working:  recrystallization.  Cold  working:  no  recrystallization.  Annealing:  Stress  relief:  reduce  stress  by  plastic  deformation;  not  uniformed  cooling.  Spherodize:  for  steel,  make  steel  soft  and  ductile,   longer   time.  Full   anneal:  make  a  material   softer.  Normalize:  Steel;deform  steel   to  grow   large  grain.  Process  Anneal:  Notify  the  effect  of  cold  work.  Hardenability:  4in  heigh,  1in  in  diameter.  Diffusion:  Interdiffusion;  self  diffusion;  vacancy  diffusion;  interstitial  diffusion