MSE 220 Fall 2019 - Quiz 4
October 31, 2019
Name: _______Solution___________________________
Discussion 101 102 103 104 105
Honor Pledge (write out):
______________________________________________________________________________
______________________________________________________________________________
Signature: ________________________________
1
, 1. (9 pts) Use the phase diagram on the next page to answer the following:
a. A sample of the alloy Fe 0.5 wt% C is heated to 1200°C and then slowly cooled to 400ºC.
After cooling this alloy to 400°C, answer the following. Clearly label your work and be sure to
show and separately label any compositions you determined and used in your calculations.
What phases are present? What is the fraction of each phase present?
α and Fe3C
Cα ~ 0.01 wt% C CFe3C = 6.7 wt% C Co = 0.5 wt% C
𝐶𝐶𝐹𝐹𝐹𝐹3 𝐶𝐶 − 𝐶𝐶𝑜𝑜 6.7 − 0.5
𝑊𝑊𝛼𝛼 = = = 0.927
𝐶𝐶𝐹𝐹𝐹𝐹3 𝐶𝐶 − 𝐶𝐶𝛼𝛼 6.7 − 0.01
𝐶𝐶𝑜𝑜 − 𝐶𝐶𝛼𝛼 0.5 − 0.01
𝑊𝑊𝐹𝐹𝐹𝐹3 𝐶𝐶 = = = 0.073
𝐶𝐶𝐹𝐹𝐹𝐹3 𝐶𝐶 − 𝐶𝐶𝛼𝛼 6.7 − 0.01
What microconstituents are present? What is the fraction of each microconstituent present?
Proeutectoid α and eutectoid α + Fe3C layered structure
Determine amounts of α and γ at temperature just above eutectoid to determine how much of
each microconstituent is present after the transformation
Cο = 0.5 wt% C Cα = 0.022 wt% C Cγ = 0.76 wt% C
𝐶𝐶𝑜𝑜 − 𝐶𝐶𝛼𝛼 0.5 − 0.022
𝑊𝑊𝛾𝛾 = = = 0.648
𝐶𝐶𝛾𝛾 − 𝐶𝐶𝛼𝛼 0.76 − 0.022
𝐶𝐶𝛾𝛾 − 𝐶𝐶𝑜𝑜 0.76 − 0.5
𝑊𝑊𝛼𝛼 = = = 0.352
𝐶𝐶𝛾𝛾 − 𝐶𝐶𝛼𝛼 0.76 − 0.022
All of the γ becomes the eutectoid α + Fe3C so the fractions of microconstituents are
𝑊𝑊𝑝𝑝𝑝𝑝𝑝𝑝−𝛼𝛼 = 0.352 𝑊𝑊𝛼𝛼+𝐹𝐹𝐹𝐹3 𝐶𝐶 = 0.648
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October 31, 2019
Name: _______Solution___________________________
Discussion 101 102 103 104 105
Honor Pledge (write out):
______________________________________________________________________________
______________________________________________________________________________
Signature: ________________________________
1
, 1. (9 pts) Use the phase diagram on the next page to answer the following:
a. A sample of the alloy Fe 0.5 wt% C is heated to 1200°C and then slowly cooled to 400ºC.
After cooling this alloy to 400°C, answer the following. Clearly label your work and be sure to
show and separately label any compositions you determined and used in your calculations.
What phases are present? What is the fraction of each phase present?
α and Fe3C
Cα ~ 0.01 wt% C CFe3C = 6.7 wt% C Co = 0.5 wt% C
𝐶𝐶𝐹𝐹𝐹𝐹3 𝐶𝐶 − 𝐶𝐶𝑜𝑜 6.7 − 0.5
𝑊𝑊𝛼𝛼 = = = 0.927
𝐶𝐶𝐹𝐹𝐹𝐹3 𝐶𝐶 − 𝐶𝐶𝛼𝛼 6.7 − 0.01
𝐶𝐶𝑜𝑜 − 𝐶𝐶𝛼𝛼 0.5 − 0.01
𝑊𝑊𝐹𝐹𝐹𝐹3 𝐶𝐶 = = = 0.073
𝐶𝐶𝐹𝐹𝐹𝐹3 𝐶𝐶 − 𝐶𝐶𝛼𝛼 6.7 − 0.01
What microconstituents are present? What is the fraction of each microconstituent present?
Proeutectoid α and eutectoid α + Fe3C layered structure
Determine amounts of α and γ at temperature just above eutectoid to determine how much of
each microconstituent is present after the transformation
Cο = 0.5 wt% C Cα = 0.022 wt% C Cγ = 0.76 wt% C
𝐶𝐶𝑜𝑜 − 𝐶𝐶𝛼𝛼 0.5 − 0.022
𝑊𝑊𝛾𝛾 = = = 0.648
𝐶𝐶𝛾𝛾 − 𝐶𝐶𝛼𝛼 0.76 − 0.022
𝐶𝐶𝛾𝛾 − 𝐶𝐶𝑜𝑜 0.76 − 0.5
𝑊𝑊𝛼𝛼 = = = 0.352
𝐶𝐶𝛾𝛾 − 𝐶𝐶𝛼𝛼 0.76 − 0.022
All of the γ becomes the eutectoid α + Fe3C so the fractions of microconstituents are
𝑊𝑊𝑝𝑝𝑝𝑝𝑝𝑝−𝛼𝛼 = 0.352 𝑊𝑊𝛼𝛼+𝐹𝐹𝐹𝐹3 𝐶𝐶 = 0.648
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