EIT Materials Science 3

Question 1

During quenching, steel is rapidly cooled in order to:

Accepted Answer

Trap carbon in a supersaturated solid solution, forming hard martensite

Answer

Slowly relieve internal stresses and soften the material

Answer

Produce a coarse pearlite microstructure for machinability

Answer

Cool uniformly in air from the austenitizing temperature

Question 2

Martensite in steel is characterized by:

Accepted Answer

A hard body-centered tetragonal (BCT) structure formed by diffusionless transformation

Answer

A soft FCC structure with high carbon solubility

Answer

A thermodynamically stable equilibrium phase

Answer

A mixture of ferrite and cementite lamellae

Question 3

The lever rule in a binary phase diagram is used to determine:

Accepted Answer

The mass fractions of each phase in a two-phase region

Answer

The temperature of the eutectic reaction

Answer

The solidus and liquidus temperatures

Answer

The rate of solidification of an alloy

Question 4

The primary purpose of tempering quenched steel is to:

Accepted Answer

Reduce brittleness while retaining useful hardness

Answer

Increase hardness and strength beyond the as-quenched condition

Answer

Dissolve carbides to create uniform austenite

Answer

Convert retained austenite to ferrite

Question 5

Which class of polymers cannot be re-melted after initial setting because of their network structure?

Accepted Answer

Thermosets

Answer

Thermoplastics

Answer

Elastomers

Answer

Semi-crystalline polymers

Question 6

The primary strengthening mechanism in precipitation hardening (age hardening) is:

Accepted Answer

Fine coherent precipitates impeding dislocation motion

Answer

Grain boundary strengthening through grain refinement

Answer

Work hardening from cold plastic deformation

Answer

Solid solution strengthening from alloying elements in solution

Question 7

Compared to metals, ceramics are generally characterized by:

Accepted Answer

High hardness, brittleness, and low electrical conductivity

Answer

Higher electrical conductivity and lower hardness

Answer

High ductility and moderate hardness

Answer

Low melting points and high thermal conductivity