Chapter 4 - Solidification Flashcards
Grain
Individual crystals in a Poly-Crystalline Metal
Grain Boundary
Location where grains meet
The finer the grain, the stronger the material
True
Fine Grain Structures
Strongest
Less Ductile
Many nucleation Sites
Coarse Grain Structures
Weakest
More Ductile
Equiaxed Grains
Crystals spread(Grow) equally in all directions and have random orientations
Columnar Grains
Long, thin grains in a solidified poly crystalline structure. Formed in the interior of ingots
Alloy
Mixture of two or more metals or materials or a metal & Non-metal
Solid Solution
Atoms are added to host material. Crystal Structure is maintained, No new structures formed.
A) Substitutional
B) Interstitial
Substitutional Solid Solution
Solute or impurity atom replaces host atom.
Must meet requirements of Hume-Rothery Rules
CEO 15
Hume-Rothery Rules
CEO 15 Same Crystal Structure Similar Electronegativity Same Charge/Valence Radii Differ by <= 15%
Interstitial Solid Solution
Impurity atoms fill voids among host atoms
Diameter must be substantially smaller
Case Hardening
Outer surface of material is hardened
Gas Carbourizing
Hardening by the addition of Hydrocarbon gas to the surface of a metal
Point Defects
Vacancy Interstitialcy Substitutional Frenkel Schottkey
Vacancy
Empty spot in crystal structure where atom should have been
Interstitialcy
Extra atom added into crystal structure
Substitutional
Alternate atom placed in location of previous atom. Structure un-altered
Frenkel
Smaller atom reloctes. Old space left vacant.
Schottkey
Both large and small molecule missing
Line Defects
Edge Dislocation
Screw Dislocation
Edge Dislocation
Extra Row/ Missing Row
Screw Dislocation
Shear stress applied. creates helical ramp
Planar Defects
Grain Boundary
Twin Boundary
Grain Boundary
Location where two crystals with different orientations meet
Twin Boundary
Region in which a mirror image of the structure exists
