Main Answer:
1. False. In metals, there are significantly more interstitials than vacancies. This is because metals have a close-packed crystal structure, leading to a higher number of interstitial spaces compared to vacancies.
2. (a) Vacancy diffusion. Diffusion by the vacancy mechanism occurs more rapidly in metal alloys.
Step-by-step explanation:
In metals, the crystal lattice structure is closely packed, and vacancies occur when some of the metal atoms are missing from their lattice positions. However, the number of vacancies is relatively small compared to the total number of lattice sites.
On the other hand, interstitials are atoms that occupy spaces between the lattice points and are less common in metals than vacancies. Therefore, the statement that there are significantly more vacancies than interstitials in metals is false. In fact, there are more interstitial spaces due to the close-packed nature of metal crystal structures.
Regarding diffusion mechanisms in metal alloys, the movement of atoms can occur through either interstitial or vacancy diffusion. Vacancy diffusion is generally more rapid in metal alloys. This is because atoms can more easily move into and out of the vacant lattice sites, allowing for faster diffusion compared to the mechanism where atoms move through the interstitial spaces.
Understanding these diffusion mechanisms is crucial in materials science, as it influences properties like hardness, strength, and conductivity in metal alloys, contributing to the design and optimization of materials for various applications.