METE230 - Chapter 4

Which of the following is NOT a point defect?

• Vacancy

• Interstitial atom

• Edge dislocation

• Substitutional impurity

Which type of dislocation has a Burgers vector perpendicular to the dislocation line?

• Edge dislocation

• Screw dislocation

• Mixed dislocation

• Planar dislocation

The number of vacancies in a material increases exponentially with:

• Temperature

• Stress

• Grain size

• Atomic radius

Which of the following best describes a grain boundary?

• A perfect alignment of atoms in a lattice

• The region between two differently oriented crystals

• A type of point defect

• A one-dimensional defect

What happens when a substitutional impurity atom is larger than the host atoms?

• It creates a vacancy

• It has no effect on the lattice

• It causes distortion in the lattice

• It produces compressive strain in the lattice

Which type of dislocation results in a helical atomic arrangement around the core?

• Edge dislocation

• Screw dislocation

• Mixed dislocation

• Interstitial dislocation

Grain boundaries generally have:

• Lower energy than the bulk material

• Higher energy than the bulk material

• No effect on mechanical properties

• A perfect atomic arrangement

Which of the following statements about twin boundaries is TRUE?

• They separate grains with the same crystallographic orientation

• They occur due to atomic diffusion

• They lead to a mirror-image misorientation

• They are the same as grain boundaries

In polycrystalline materials, smaller grain size generally leads to:

• Increased strength

• Decreased hardness

• Lower dislocation density

• Increased ductility

What is the primary difference between an interstitial defect and a substitutional defect?

• The location of the impurity atom

• The effect on electrical conductivity

• The charge of the impurity atom

• The change in crystal structure