Question 1

Which of the following best describes a vacancy defect in a crystalline solid?

Accepted Answer

A lattice site where an atom is missing

Question 2

Why are pure metals generally NOT desirable for engineering applications?

Accepted Answer

Pure metals lack the improved properties that result from controlled impurities and alloying

Question 3

Which of the following is NOT a point defect in metals?

Accepted Answer

Dislocation

Question 4

According to the equation $$N_v = N \exp\left(\frac{-Q_v}{kT}\right)$$, what happens to the number of vacancies $$N_v as $$temperature $$T$$ increases?

Accepted Answer

It increases exponentially with temperature

Question 5

Which factor is NOT part of the Rothery rules for substitutional solid solutions?

Accepted Answer

Melting point

Question 6

A self-interstitial defect occurs when:

Accepted Answer

A host atom occupies an interstitial site

Question 7

Which of the following is a requirement for complete solubility in substitutional solid solutions according to the Rothery rules?

Accepted Answer

The solute and solvent must have similar atomic radii (difference less than 15%)

Question 8

In an interstitial solid solution, the concentration of solute atoms should be:

Accepted Answer

Less than 10% of host atoms

Question 9

Which of the following is a two-dimensional defect in solids?

Accepted Answer

Boundary

Question 10

Given the equation $$N_v = N \exp\left(\frac{-Q_v}{kT}\right)$$, which parameter is typically determined experimentally?

Accepted Answer

$$Q_v ($$energy required for the formation of a vacancy)

Question 11

Which of the following statements about solid solutions is TRUE?

Accepted Answer

Solid solutions are formed when solute atoms are added to host material and the structure remains homogeneous

Question 12

If the atomic radius of copper is $$0.128\ \mathrm{nm}$$ and that of nickel is $$0.125\ \mathrm{nm}$$, what is the percent difference in atomic radii, and does this satisfy the Rothery rule for substitutional solid solutions?

Accepted Answer

2.4%, which satisfies the Rothery rule

Question 13

Which of the following is an example of an interstitial solid solution?

Accepted Answer

Carbon in iron

Question 14

What is the main reason the number of vacancies in a metal increases with temperature?

Accepted Answer

Atomic vibration increases with temperature, making it easier for atoms to leave their lattice sites

Question 15

Which of the following is NOT a plausible outcome when an impurity atom is added to a host metal?

Accepted Answer

Formation of a completely new crystal structure

Question 16

A steel alloy is made by adding carbon to iron. Which type of defect is primarily introduced?

Accepted Answer

Interstitial impurity

Question 17

Which of the following is TRUE regarding the formation of vacancies during solidification?

Accepted Answer

Vacancies are formed due to atomic vibrations

Question 18

Which of the following is a one-dimensional defect in solids?

Accepted Answer

Dislocation

Question 19

Which of the following is NOT a plausible effect of adding impurities to a metal?

Accepted Answer

Formation of a completely pure metal

Question 20

Which of the following statements about the equilibrium number of vacancies $$N_v in a $$metal is correct?

Accepted Answer

$$N_v$$ decreases as the energy required for vacancy formation $$Q_v$$ increases

Imperfections in Solids: Defects and Impurities in Metals

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