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Matse 259 Final Exam Prep Questions And Answers
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Matse 259 Final Exam Prep Questions And Answers
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Solution 2024/2025Pepper
Matse 259 Final Exam Prep Questions And
Answers
What is important in the Austenite --> Pearlite Transformation ANS✔✔ Temperature, Rate of transformation (S-Curve)
for a eutectoid alloy_______temp (decreased supercooling), _______ the rate of transformation ANS✔✔ for a eutectoid
alloy increasing temp (decreased supercooling), slows down the rate of transformation
Austenite --> Pearlite transformation occurs only if an alloy is _______to a temp ______ the eutectoid. ANS✔✔
Austenite --> Pearlite transformation occurs only if an alloy is supercooled to a temp below the eutectoid.
Austenite --> Pearlite transformation at temps ______ the eutectoid, it takes a ______ time to reach 50%
transformation. ANS✔✔ Austenite --> Pearlite transformation at temps just below the eutectoid, it takes a longtime to
reach 50% transformation.
Austenite --> Pearlite transformation at higher levels of undercooling, the transformation occurs much more _______.
ANS✔✔ Austenite --> Pearlite transformation at higher levels of undercooling, the transformation occurs much more
Rapidly.
Coarse Pearlite at a temp just below the eutectoid, thick layers of ferrite and cementite form, and _____ diffusion allows
C atoms to diffuse ______ distances and creates a _______ Lamellae. ANS✔✔ Coarse Pearlite at a temp just below the
eutectoid, thick layers of ferrite and cementite form, and high diffusion allows C atoms to diffuse long distances and
creates a thick Lamellae.
Pic
Fine Pearlite at a temp just below the eutectoid, thin layers of ferrite and cementite form, and _____ diffusion allows C
atoms to diffuse ______ distances and creates a _______ Lamellae. Forms at 540 degrees Celsius ANS✔✔ Fine Pearlite
at a temp just below the eutectoid, thin layers of ferrite and cementite form, and lower diffusion rates allows C atoms to
diffuse short distances and creates a thin Lamellae.
Forms at 540 degrees Celsius
, Solution 2024/2025
Pepper
Pic
In addition to pearlite, other microconstituents are formed during the transformation from the austenite phase. Those
include ________, _________, __________. ANS✔✔ In addition to pearlite, other microconstituents are formed during
the transformation from the austenite phase, those include Bainite, Spheroidite, Martensite .
Bainite consists of __________and _________ phases and is formed by diffusional processes. ANS✔✔ Bainite consists of
ferrite and cementite phases and is formed by diffusional processes.
Bainite forms as ________ or ________, depending on the temperature of the transformation. Fine microstructure-->
electron microscope needed. ANS✔✔ Bainite forms as needles or plates, depending on the temperature of the
transformation. Fine microstructure--> electron microscope needed.
If a _____ or _____ microstructure is held at a temperature below the eutectoid for 18 to 24 h, a _______microstructure
will form. ANS✔✔ If a pearlitic or bainitic microstructure is held at a temperature below the eutectoid for 18 to 24 h, a
spheroidite microstructure will form.
Cementite appears as _____-like particles embedded in a ferrite matrix. ANS✔✔ Cementite appears as sphere-like
particles embedded in a ferrite matrix.
Transformation occurs by additional _____ diffusion with no change in composition ANS✔✔ Transformation occurs by
additional carbon diffusion with no change in composition
Martensite forms when ______ is _______ cooled (quenched) to a relatively low temperature. ANS✔✔ Martensite
forms when austenite is rapidly cooled (quenched) to a relatively low temperature.
It is a _____ single phase structure that results from a diffusion-less transformation of _____. Quenching rate is rapid
enough to ______ carbon diffusion. ANS✔✔ It is a non-equilibrium single phase structure that results from a diffusion-
less transformation of austenite. Quenching rate is rapid enough to prevent carbon diffusion.
Martensite has what type of crystal structure? ANS✔✔ BCT
, Solution 2024/2025
Pepper
Martensitic transformation is _____ of time and is only a function of the _____ to which the alloy is quenched (athermal
transformation) ANS✔✔ Martensitic transformation is independent of time and is only a function of the temperature to
which the alloy is quenched (athermal transformation).
Most heat treatments for steels involve the ____ of a specimen to ______ temperature. ANS✔✔ Most heat treatments
for steels involve the continuous cooling of a specimen to room temperature.
An isothermal transformation diagram is valid only for conditions of _______ temperature ANS✔✔ An isothermal
transformation diagram is valid only for conditions of constant temperature
Normally, bainite _____ form at the eutectoid composition ANS✔✔ Normally, bainite will not form at the eutectoid
composition
For any cooling curve that passes through Austenite to Pearlite trans. region, the pearlite transformation ceases and
with continued cooling, the remaining austenite is transformed to martensite. ANS✔✔ For any cooling curve that passes
through Austenite to Pearlite trans. region, the pearlite transformation ceases and with continued cooling, the
remaining austenite is transformed to martensite.
At the ______, 100% martensite will form. ANS✔✔ At the ______, 100% martensite will form.
Only martensite will exist at quenching rates greater than the critical. ANS✔✔ Only martensite will exist at quenching
rates greater than the critical.
A totally _______ structure develops for low cooling rates. ANS✔✔ A totally pearlitic structure develops for low cooling
rates.
We alloy steels to facilitate the formation of _____ with relatively ______ cross sections. ANS✔✔ We alloy steels to
facilitate the formation of martensite with relatively thick cross sections.
Critical cooling rate is ______ even by the presence of carbon. ANS✔✔ Critical cooling rate is diminished even by the
presence of carbon.
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