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Answer:
B. The Hall-Petch Relation
Explanation:
The Hall-Petch relation indicates that by reducing the grain size the strength of a material is increased up to the theoretical strength of the material however when the material grain size is reduced below 20 nm the material is more susceptible to creep deformation and displays an "inverse" Hall-Petch Relation as the Hall-Petch relation then has a negative slope (k value)
The Hall-Petch relation can be presented as follows;
[tex]\sigma_y[/tex] = [tex]\sigma_0[/tex] + k·(1/√d)
Where;
[tex]\sigma_y[/tex] = The strength
σ₀ = The friction stress
d = The grain size
k = The strengthening coefficient
The model equation for the reverse Hall-Petch effect is presented here as follows;
[tex]\sigma_y[/tex] = 10.253 - 10.111·(1/√d)