Materials Science Flashcards
7 cards from real BME 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
In the iron-carbon phase diagram, cementite (Fe3C) contains what weight percentage of carbon?
Answer: 6.70 wt%
Cementite (iron carbide, Fe3C) has a fixed stoichiometric composition of 6.70 wt% carbon.
Which type of bonding is responsible for the unique properties of graphite, including its lubricity and electrical conductivity?
Answer: Covalent bonding within layers and van der Waals forces between layers
Graphite has sp2 covalent bonding within hexagonal layers and delocalized π electrons that provide conductivity, with weak van der Waals forces between layers enabling easy shear.
A material tested in tension shows a distinct upper and lower yield point followed by Lüders band propagation. This behavior is characteristic of:
Answer: Low-carbon steels with interstitial solute pinning
In low-carbon steel, interstitial carbon and nitrogen atoms pin dislocations; the upper yield point corresponds to unpinning, after which Lüders bands propagate.
The glass transition temperature (Tg) of an amorphous polymer marks the transition from:
Answer: Glassy (rigid) to rubbery (viscoelastic) behavior
Below Tg, polymer chain segments are frozen; above Tg, segmental motion becomes possible, giving rubbery, viscoelastic behavior.
Which non-destructive testing method uses high-frequency sound waves to detect internal flaws in materials?
Answer: Ultrasonic testing
Ultrasonic testing sends high-frequency acoustic waves into a material and detects reflections from internal discontinuities like cracks and voids.
In precipitation hardening (age hardening), the maximum strength is achieved at the stage called:
Answer: Peak aging
Peak aging produces the optimal precipitate size and distribution that maximally impedes dislocation motion, giving maximum hardness and strength.
The Peierls-Nabarro stress is the theoretical stress required to:
Answer: Move a dislocation through a perfect crystal lattice
The Peierls-Nabarro stress represents the lattice friction stress that must be overcome to move a dislocation one Burgers vector in a perfect crystal.