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Grain Boundaries Ni-Base Superalloy Waspalloy 50µm high-angle grain boundary (  >15°) low-angle grain boundary.

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Presentation on theme: "Grain Boundaries Ni-Base Superalloy Waspalloy 50µm high-angle grain boundary (  >15°) low-angle grain boundary."— Presentation transcript:

1 Grain Boundaries Ni-Base Superalloy Waspalloy 50µm high-angle grain boundary (  >15°) low-angle grain boundary

2 Properties of Materials Mechanical Properties Elastic Plastic Viscoelastic Creep Testing methods

3 The Tensile Test stress  =F/A strain  =l-l 0 /l 0

4 The Tensile Test

5 Elastic Deformation distance r r0r0 Force=dE/dr

6 Elastic constants (isotropic case) Stress – strain / shear stress – shear strain Young’s 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  Y strain offset yield-point phenomenon (C steels, dislocations are pinned by C) YY YY

8 The Stress-Strain Curve stress strain necking engineering stress true stress

9 Materials Selection Charts Strength [MPa] Density [1000kg/m³]

10 Plastic Deformation – Dislocation Glide shear stress 

11 Plastic Deformation – Dislocation Glide =>macroscopic deformation

12 Plastic Deformation – Dislocation Glide dislocation motion

13 Plastic Deformation shear stress 

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 length of the diagonals d 1 and d 2

17 Rockwell Hardness Testing (HRC) scale indenter (120° diamond pyramid) specimen

18 Ductility stress strain %EL, percent elongation %RA, percent reduction in area brittle ductile

19 Charpy Impact Testing hammer impact energy A v =mg(h-h´) specific a k =A v /A 0 (DIN 50115)

20 T-Dependence of Av BDTT

21 Cleavage Fracture at Low Temperatures

22 Deformation at Elevated Temperatures: Creep 

23 Creep Testing d  dt

24 Fatigue Loading during Service

25 Fatigue Testing

26 push-pull rotating-bending counter load servohydraulic actuator

27 Fatigue-Testing: The S/N Diagram stress amplitude [MPa] cycles to failure N fatigue limit total life design

28 Fracture Mechanics K Ic represents resistance to brittle fracture [MPam 0.5 ]

29 Determination of K Ic using Compact Tension (CT specimens) extensometer force displacement


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