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Why is it difficult to transmit dislocations across a grain boundary?
Slip plane isn’t continuous
Orientation of next grain = different hence τcrss = different
Obstacle effect
Dislocations encountering the grain boundary pile-up at the obstacle
At linear bit in beginning, no work hardening as no boundaries for dislocations to be stuck hence keeps sliding
Work hardening coefficient
dτ = change in shear stress
dγ = change in shear strain
Complexity effect
This is due to the availability of many slip systems in a polycrystal consisting of randomly oriented grains
Energy to deform crystal by some amount:
σdε = Στdγ (sum of all the single crystal shear strains at the shear stress)
