EIT Materials Science

Question 1

What is the coordination number for an atom in a face-centered cubic (FCC) crystal structure?

Accepted Answer

12

Answer

In an FCC structure, each atom is surrounded by 12 nearest neighbors, giving a coordination number of 12.

Question 2

Which of the following crystal structures has the highest atomic packing factor (APF)?

Accepted Answer

Face-centered cubic (FCC)

Answer

FCC has an APF of 0.74, which is the highest among the listed structures (BCC = 0.68, SC = 0.52, diamond = 0.34).

Question 3

At what temperature does the eutectoid reaction occur in the iron-carbon phase diagram?

Accepted Answer

727°C

Answer

The eutectoid reaction (austenite → ferrite + cementite) occurs at 727°C and 0.76 wt% C, producing pearlite.

Question 4

What is the eutectoid composition in the iron-carbon phase diagram?

Accepted Answer

0.76 wt% C

Answer

The eutectoid point occurs at 0.76 wt% C, where austenite transforms directly to pearlite (ferrite + cementite) at 727°C.

Question 5

What type of point defect involves a missing atom at a lattice site?

Accepted Answer

Vacancy

Answer

A vacancy is a point defect where an atom is absent from its regular lattice position.

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