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Grain Boundaries

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Grain Boundaries high-angle grain boundary (Q15 ) Ni-Base Superalloy Waspalloy low-angle grain boundary 50 m Properties of Materials The Tensile Test The Tensile ... – PowerPoint PPT presentation

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Title: Grain Boundaries


1
Grain Boundaries
high-angle grain boundary (Qgt15)
2
Properties of Materials
  • Mechanical Properties
  • Elastic
  • Plastic
  • Viscoelastic
  • Creep
  • Testing methods

3
The Tensile Test
4
The Tensile Test
5
Elastic Deformation
distance r
6
Elastic constants (isotropic case)
  • Stress strain / shear stress shear
    strain
  • Youngs modulus
  • Shear modulus
  • Poisson ratio
  • In order to completely describe the elastic
    behavior of a solid 2 of these constants need to
    be known!

7
Yield Strength sY
yield-point phenomenon (C steels, dislocations
are pinned by C)
0.002 strain offset
8
The Stress-Strain Curve
stress
necking
strain
9
Materials Selection Charts
Strength MPa
Density 1000kg/m³
10
Plastic Deformation Dislocation Glide
11
Plastic Deformation Dislocation Glide
gtmacroscopic deformation
12
Plastic Deformation Dislocation Glide
dislocation motion
13
Plastic Deformation
shear stress t
14
Some concluding words on dislocations
  • Strengthening mechanisms
  • Grain size reduction (Hall-Petch equation)
  • Solid solution strengthening
  • Strain hardening

15
Mechanical testing
  • Hardness
  • Vickers
  • Rockwell
  • Nanoindentation
  • Ductility
  • Toughness
  • Creep
  • Fatigue

16
Vickers Microhardness Testing
17
Rockwell Hardness Testing (HRC)
scale
indenter (120 diamond pyramid)
specimen
18
Ductility
stress
strain
19
Charpy Impact Testing
impact energy Avmg(h-h) specific akAv/A0
hammer
(DIN 50115)
20
T-Dependence of Av
21
Cleavage Fracture at Low Temperatures
22
Deformation at Elevated Temperatures Creep
23
Creep Testing
24
Fatigue Loading during Service
25
Fatigue Testing
26
Fatigue Testing
rotating-bending
push-pull
load
counter
servohydraulic actuator
27
Fatigue-Testing The S/N Diagram
stress amplitude MPa
cycles to failure N
28
Fracture Mechanics
KIc represents resistance to brittle fracture
MPam0.5
29
Determination of KIc using Compact Tension (CT
specimens)
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