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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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.