Question

Because the mechanism of creep deformation is different from the mechanism of slip in most metal deformation processes, one of the fundamental relationships between microstructure and mechanical properties of metals is reversed for creep deformation compared with normal deformation. Is it:________.

A. The Hume-Rothery Rules
B. The Hall-Petch Relation
C. The Schmid Equation

Answer 1

B. The Hall-Petch Relation

Step-by-step 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;

`\sigma_y` =
`\sigma_0` + k·(1/√d)

Where;

`\sigma_y` = 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;

`\sigma_y` = 10.253 - 10.111·(1/√d)