Problem $5$

For each of the following statements, indicate whether the statement is true or false.

Justify $($explain$)$ your answer.

$($i$)$ Low bond energies are associated with high thermal expansion coefficients.

$($ii$)$ BCC crystals do not contain dislocations.

$($iii$)$ When materials are subjected to a tensile stress, the lateral strain is

always negative.

$($iv$)$ Both the tensile strength and the yield strength of a metal can be

increased by alloying.

$($v$)$ Recrystallization cannot occur at room temperature.

$($vi$)$ Diffusion in crystalline solids can only occur if there are vacancies in

the crystals.