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Development of Microstructure
an mpor ance o cros ruc ure
in Materials Selection
Dept. of Metall. & Mater. Engg.
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Use of Materials over ages
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Some Design Criteria in the
e ec on o a er a s
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Materials-Processing Pyramid
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Precipitation Hardening in the First Aerospace
Alluminum Alloy: The Wright Flyer Crankcase An aluminum copperalloy (with a Cu composition of 8wt%) was used in the engine that powered the historicfirst fl i ht of the Wri ht brothers in 1903.
In 1906, Wilm, accidentally discovered age hardening. 1938: Guinier and Preston (x-ray); 1950-60 TEM
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High Temperature Applications: Turbine Blades
Grain vs. Grain Boundary
.
Precipitation vs. Dispersion Hardening
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Strengthening by
ra n e nement
As Cast
Structure
As Cast
Fine GrainStructure
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Grain Boundary Strengthening
20010-1 10-2 5x10-3
grain size, d (mm)
slip planein
B Pa)
150
gr
ain
grain Ag
yi
eld(
50
100
1
y
oundar
-0.5
04 8 12 160
yield = o + kyd1/2
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Effect of Grain refinement on the
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Combined Grain Refinement &
-
Modification
200X
8000X
Modification
(1M13+ 0.02Sr) (5min) 200X
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Load Bearing Capacity of Al-7Si alloy
400
450No GR/MOD
GR
300
350
(m/mm
3) MOD
GR+MOD
150
200
sistance
50
100
WearR
50N 60N 70N 100N 120N 150N 200NNormal Load
ng e oc y ms-
Distance 1.8 Km
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Fe-Fe3C Phase Diagram
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Microstructure evolution in Eutectoid steel
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Microstructure evolution in Hypoeutectoid steel
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Microstructure evolution in Hypereutectoid steel
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Effect of C on microstructure of steels
0% C
0.2% C
0.4% C
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0.8% C
0.6% C
1.2% C
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Pearlite
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Bainite
Upper Bainite Lower Bainite
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Martensite
Lath Martensite Plate Martensite
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Spheroidite
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Effect of C on Mech. Properties
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Effect of Microstrcture on
.
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Effect of Microstructure on
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Effect of Microstructure on
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Al-Cu Microstructures
GP zones
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Design of Microstructure in Ti alloys
/ microstructure
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High Strength Al based Nanocomposites
Al-Al Ti Nanocomposite94 4 2
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Al-Al3Fe In-situ Nanocomposites by MA
10
12Ageing time, 2hrs
Al100-X
FeX- 20h MA
green compact
6
8
rdness,
GP
573K
673K
0
2
4H
100nm
0 5 10 15 20
Composition (at % Fe)
4000
5000
as compacted
473K
Ageing time, 2hrs
Al100-X
FeX- 20h MA
,MPa
HardnessHardness
2000
3000
673K
YieldStrength
0 5 10 15 20
0
Composit ion (at % Fe)
Yield StrengthYield Strength
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High Strength Conducting Cu Based Nanocomposites
Cu Nanocomposite
Cu-W2edwithOFH
1
rationo
rmali
5 10 15 20 25 300
HR
wt.% Tungsten
900
1200
gth(MPa)
Nanocomposite
HP
Microcomposite
300
600
30nm
60nm
117nm
pressivestre
Cu-20%Ta at
500oC
5 20 30
0
Co
Wt. % Tungsten
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Microstructure Development
Polishing Emery Paper polishing
Cloth Polishing
Electropolishing
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Polishing
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Principle of Etching
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Effect of Grain
r en a on
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Functioning of an Optical Microscope
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=
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Effect of wavelength
680nm 550nm 470nm
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Effect of Numerical Aperture
1.25 0.65
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Bright Field Image
Dark Field Image
S i El t Mi t IIT M d
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Scanning Electron Microscope at IIT Madras
Transmission Electron Microscope at IIT Madras
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Transmission Electron Microscope at IIT Madras
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High resolution micrograph from an icosahedral
quasicrystal showing five fold symmetry (Courtesy K. I. Hiraga)
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Crystal vs.
Amorphous
Aberration corrected TEM
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Aberration corrected TEM
Atom Probe Tomography: LEAP
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Atom Probe Tomography: LEAP
AlCrCuNiZnCo compacted at
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p
600C & 650MPa
1 Million atoms
AlCrCuNiZnFe compacteda a
20 Million atoms
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