L9 - Precipitate hardening

Precipitate hardening graph cutting

F = λτb

e.g. As λ decreases, the stress to cause dislocation detachment τ increases

Bowing

At high r, F increases until f becomes zero. At these high F, the dislocation can bypass the particle by leaving a dislocation loop (Orowan loop) around the particle

Twinning

• Favoured at low temperatures and high strain rates – both situations where thermal activation of dislocations is hard.