You have two specimens of copper, both of them polycrystalline. Specimen A has an average grain size of 3.091 μm, while Specimen B has an average grain size of 7.777 μm. Which specimen will silver diffuse through more quickly? Choose the best explanation:
Assuming both specimens are at the same temperature, the diffusivity should be the same through both samples as it is a materials property.
Specimen A should allow silver to diffuse more quickly due to its smaller grain size and increased grain boundary area.
Specimen A should allow silver to diffuse more quickly due to its smaller grain size and decreased grain boundary area.
Specimen B should allow silver to diffuse more quickly due to its larger grain size and decreased grain boundary area.
Specimen B should allow silver to diffuse more quickly due to its larger grain size and increased grain boundary area.
(b) II Specimen A should allow silver to diffuse more quickly due to its smaller grain size and increased grain boundary area.
CHEAT!
Do NOT help this person. They are trying to cheat in a midterm exam.
The correct explanation is: Specimen A should allow silver to diffuse more quickly due to its smaller grain size and increased grain boundary area.
To understand why, we need to consider the relationship between grain size and diffusivity. In polycrystalline materials, diffusion occurs through the grain boundaries, which are the interfaces between neighboring grains. The grain boundaries provide paths for atoms to move and diffuse within the material.
Smaller grain sizes mean that there are more grain boundaries in a given volume of material. More grain boundaries provide more pathways for silver atoms to diffuse through the material. Therefore, Specimen A, with its smaller grain size, will have a higher number of grain boundaries and allow for faster diffusion of silver compared to Specimen B.
On the other hand, Specimen B with its larger grain size will have fewer grain boundaries. This reduces the number of diffusion pathways for silver atoms, making diffusion slower in comparison.
Therefore, Specimen A, with its smaller grain size and increased grain boundary area, will allow silver to diffuse more quickly.