ME Metals and Alloys

Question 1

Which crystal structure do most face-centered cubic (FCC) metals exhibit at room temperature?

Accepted Answer

FCC

Answer

Metals such as aluminum, copper, gold, silver, and nickel have an FCC crystal structure with atoms at cube corners and face centers.

Question 2

The iron-carbon phase diagram shows that the maximum solubility of carbon in austenite (FCC iron) is approximately:

Accepted Answer

2.14 wt%

Answer

Austenite can dissolve up to 2.14 wt% carbon at 1147 degrees C; beyond this, cementite (Fe3C) forms, and compositions above 2.14 wt% C are classified as cast irons.

Question 3

The eutectoid composition in the iron-carbon system is approximately:

Accepted Answer

0.77 wt% C

Answer

At 0.77 wt% C and 727 degrees C, austenite transforms to pearlite (alternating layers of ferrite and cementite) in the eutectoid reaction.

Question 4

Age hardening (precipitation hardening) in aluminum alloys involves which sequence of steps?

Accepted Answer

Solution treatment, quenching, aging

Answer

Precipitation hardening requires solution treatment to dissolve alloying elements, rapid quenching to create a supersaturated solid solution, then aging to precipitate fine strengthening particles.

Question 5

Martensite in steel is formed by:

Accepted Answer

Rapid quenching that suppresses diffusional transformation

Answer

Martensite forms by a diffusionless, shear-type transformation when austenite is rapidly quenched, trapping carbon in a body-centered tetragonal structure.

ME - Materials Engineer Practice Test

ME - Materials Engineer Practice Test

ME Metals and Alloys