2/15/2002, Friday

Strengthening Mechanisms

Strengthening Philosophy

Plastic deformation is due to the motion of alarge number of dislocations;

Strength (resistance to deformation) can be improved by putting obstacles to slip

Polycrystalline metalsvs.

single crystals,which one is stronger?

Dislocation in polycrystalline

Strengthening by grain size reduction

The finer the grains, the larger the area of grain boundaries that impedes dislocation motion.

Grain growth

Strain-hardening

Ductile metals become stronger when they are deformed plastically.

Dislocation stress fields

Dislocation - dislocation interaction

Chinese ancient sword

Chinese Han Dynasty, Bronze Sword, 206BC

Japanese ancient sword

Samurai

Solid Solution Strengthening

Precipitation Hardening