Materials Science Flashcards
7 cards from real Fundamentals of Engineering practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Materials Science flashcards as text
On the iron-carbon phase diagram, the eutectoid composition is approximately:
Answer: 0.76 wt% C
The eutectoid point occurs at 0.76 wt% C and 727°C, where austenite transforms isothermally to pearlite (ferrite + cementite).
Martensite in steel is formed by:
Answer: Rapid quenching of austenite
Rapid quenching of austenite traps carbon in a supersaturated body-centered tetragonal structure, producing hard, brittle martensite through a diffusionless transformation.
Which heat treatment reduces brittleness of quenched (martensitic) steel by heating below the eutectoid temperature?
Answer: Tempering
Tempering reheats martensitic steel to a sub-eutectoid temperature, allowing some carbon precipitation and relieving internal stresses to improve toughness.
The lever rule in a two-phase region of a phase diagram is used to determine:
Answer: The relative weight fractions of each phase present
The lever rule uses the tie line in a two-phase region to calculate the weight fraction of each phase present at a given overall composition and temperature.
Precipitation hardening (age hardening) increases strength by:
Answer: Generating fine precipitates throughout the matrix that obstruct dislocation motion
Fine, coherent precipitates act as obstacles that dislocations must either cut through or bypass (Orowan looping), both requiring additional stress.
The glass transition temperature (Tg) of a polymer is best described as the temperature:
Answer: Below which the polymer becomes glassy, stiff, and brittle
Below Tg, polymer chain segments lack sufficient thermal energy to rotate or translate, making the material glassy and brittle rather than rubbery.
Charpy and Izod impact tests primarily measure a material's:
Answer: Impact toughness (energy absorbed before fracture)
Both tests strike a notched specimen with a swinging pendulum and measure the energy absorbed during fracture as a measure of impact toughness.