Fundamentals of Engineering Materials Science

Question 1

What crystal structure does α-iron (ferrite) have at room temperature?

Accepted Answer

Body-centered cubic (BCC)

Answer

α-iron (ferrite) has a BCC crystal structure at room temperature, transitioning to FCC austenite above 912°C.

Question 2

Young's modulus (modulus of elasticity) is defined as:

Accepted Answer

The ratio of stress to strain in the elastic region

Answer

Young's modulus E = σ/ε is the slope of the linear portion of the stress-strain curve where deformation is fully recoverable.

Question 3

A vacancy (point defect) in a crystal lattice is best described as:

Accepted Answer

An atom missing from its normal lattice position

Answer

A vacancy (Schottky defect) is simply a missing atom at a normally occupied lattice site.

Question 4

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

Accepted Answer

12

Answer

In an FCC structure each atom touches 12 nearest neighbors: 4 in its own layer, 4 in the layer above, and 4 in the layer below.

Question 5

The Burgers vector of a dislocation represents:

Accepted Answer

The magnitude and direction of the lattice distortion caused by the dislocation

Answer

The Burgers vector characterizes a dislocation by quantifying the magnitude and direction of the lattice slip associated with it.

Fundamentals of Engineering Practice Test