Control Of Strength In Metals Flashcards
5 methods of increasing strength
Work hardening Precipitate strengthening Phase balance control Solid solution strengthening Grain size control
Affect of grain size on strength
Small grain size= higher strength
How to alter grain size (ex)
Control during processing
E.g. casting, rolling, extrusion, heat treatment
Smaller substitutions atoms create
Tensile fields
Larger substitutions atoms create
Compressive fields
Puts strain on material
Increases strength
Interstitial atoms preferentially concentrate at
Dislocation sites
Adding more…. elements …
Alloying elements
Increases the solid solution strengthening increment
What is the limitation to solid solution strengthening
If u add too much it no loner goes into solution
Phase=
A homogeneous portion of a system that has uniform physical and chemical characteristics
Why does changing the phase balance change the strength
Different phases have different properties
Some elements do not… in an .. instead they form… which…
Do not readily go into solution
In an alloy
They form discrete particles
Which strengthen the alloy
The distribution of large numbers of fine precipitates….
Prevents dislocations moving past
Applied stress has to push the dislocation line past the precipitates
With precipitates the material loses strength if
Aging causes the particles to coarsen
Dislocations shear through particles
Some materials get …. if u plastically deform them
Significantly stronger and harder
Work hardening….
Increases dislocation densities by orders of magnitude.
Makes dislocations harder to move
