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

Properties of Materials Mechanical Properties Elastic Plastic Viscoelastic Creep Testing methods

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

The Tensile Test

Elastic Deformation distance r r0r0 Force=dE/dr

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!

Yield Strength  Y strain offset yield-point phenomenon (C steels, dislocations are pinned by C) YY YY

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

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

Plastic Deformation – Dislocation Glide shear stress 

Plastic Deformation – Dislocation Glide =>macroscopic deformation

Plastic Deformation – Dislocation Glide dislocation motion

Plastic Deformation shear stress 

Some concluding words on dislocations Strengthening mechanisms Grain size reduction (Hall-Petch equation) Solid solution strengthening Strain hardening

Mechanical testing Hardness Vickers Rockwell … Nanoindentation Ductility Toughness Creep Fatigue

Vickers Microhardness Testing length of the diagonals d 1 and d 2

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

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

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

T-Dependence of Av BDTT

Cleavage Fracture at Low Temperatures

Deformation at Elevated Temperatures: Creep 

Creep Testing d  dt

Fatigue Loading during Service

Fatigue Testing

push-pull rotating-bending counter load servohydraulic actuator

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

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

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