BE/B Eng Bachelor of Engineering Materials Engineering 2

Question 1

What is the mechanism of corrosion in metals involving an electrochemical reaction?

Accepted Answer

An oxidation reaction at the anode and a reduction reaction at the cathode in the presence of an electrolyte

Answer

Electrochemical corrosion occurs when a galvanic cell forms: the anodic metal oxidizes (loses electrons) while cathodic reduction occurs at another site, with ions transported through the electrolyte.

Question 2

What is the purpose of age hardening (precipitation hardening) in aluminum alloys?

Accepted Answer

To increase strength by forming fine precipitates that impede dislocation movement

Answer

Precipitation hardening involves solution heat treatment, quenching, and controlled aging to form fine dispersed precipitates within the matrix, which block dislocation motion and increase yield strength.

Question 3

What is a composite material?

Accepted Answer

A material made from two or more constituent materials with different properties that produce a material with superior characteristics

Answer

Composites combine a reinforcement (e.g., carbon fiber, glass fiber) within a matrix (e.g., polymer resin, metal) to achieve properties neither component possesses alone, such as high strength-to-weight ratio.

Question 4

In ceramics, what causes brittleness compared to metals?

Accepted Answer

The dominance of ionic and covalent bonds that prevent dislocation movement

Answer

Ceramic brittleness arises because ionic and covalent bonds are directional and strong, preventing the dislocation slip that allows metals to deform plastically before fracturing.

Question 5

What is Fick's First Law of diffusion in materials science?

Accepted Answer

The diffusion flux is proportional to the concentration gradient (J = -D dC/dx)

Answer

Fick's First Law states J = -D(dC/dx), where J is diffusion flux, D is diffusivity, and dC/dx is the concentration gradient; flux is proportional to and opposite in direction to the gradient.

BE/B Eng Bachelor of Engineering Practice Test

BE/B Eng Bachelor of Engineering Practice Test

BE/B Eng Bachelor of Engineering Materials Engineering 2