ME Metallurgy and Phase Diagrams

Question 1

On the iron-iron carbide (Fe-Fe3C) phase diagram, what is the carbon content at the eutectoid composition?

Accepted Answer

0.76 wt% C

Answer

The eutectoid point in the Fe-Fe3C system occurs at 0.76 wt% C and 727°C, where austenite transforms to pearlite upon slow cooling.

Question 2

Pearlite is a microstructure consisting of alternating lamellae of:

Accepted Answer

Ferrite and cementite

Answer

Pearlite forms by the eutectoid reaction and consists of alternating layers of alpha-ferrite and cementite (Fe3C).

Question 3

Martensite in steel is formed by:

Accepted Answer

Rapid quenching of austenite, preventing diffusion-based transformation

Answer

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

Question 4

The Gibbs phase rule for a system in equilibrium is expressed as:

Accepted Answer

F = C - P + 2

Answer

The Gibbs phase rule F = C - P + 2 relates degrees of freedom (F), components (C), and phases (P) at equilibrium.

Question 5

In a binary phase diagram, the lever rule is used to determine:

Accepted Answer

The relative amounts (fractions) of each phase in a two-phase region

Answer

The lever rule applies the principle of mass balance to calculate the weight fractions of each phase present in a two-phase region of a phase diagram.

ME - Materials Engineer Practice Test

ME - Materials Engineer Practice Test

ME Metallurgy and Phase Diagrams