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Chapter 9: Problem 80

A steel alloy contains \(95.7 \mathrm{wt} \% \mathrm{Fe}, 4.0 \mathrm{wt} \% \mathrm{~W}\), and \(0.3 \mathrm{wt} \% \mathrm{C}\). (a) What is the eutectoid temperature of this alloy? (b) What is the eutectoid composition? (c) What is the proeutectoid phase? Assume that there are no changes in the positions of other phase boundaries with the addition of \(\mathrm{W}\).

Short Answer

Expert verified
Based on the given steel alloy composition and the assumption that the addition of Tungsten does not change the positions of other phase boundaries, the eutectoid temperature is 723°C, the eutectoid composition is 0.76 wt% C, and the proeutectoid phase is Ferrite (α-phase).

Step by step solution

01

Identify eutectoid temperature

The eutectoid temperature is the temperature at which the eutectoid transformation takes place. In our case, we are dealing with an iron-carbon phase diagram, and we can find the eutectoid temperature from the phase diagram. For a standard iron-carbon phase diagram, the eutectoid temperature occurs at 723°C. Since the addition of W doesn't change the positions of other phase boundaries, the eutectoid temperature of the given steel alloy is also 723°C.
02

Identify eutectoid composition

The eutectoid composition refers to the composition of the alloy at which the eutectoid transformation happens. From the standard iron-carbon phase diagram, the eutectoid composition is the composition of the steel alloy at the eutectoid transformation temperature. According to the iron-carbon phase diagram, the eutectoid composition occurs at 0.76 wt% C. Since the addition of W doesn't change the positions of other phase boundaries, the eutectoid composition of the given steel alloy is also 0.76 wt% C.
03

Determine the proeutectoid phase

The proeutectoid phase is the phase that forms before the eutectoid transformation occurs. The given steel alloy composition has 0.3 wt% C, which is to the left of the eutectoid composition (0.76 wt% C) on the iron-carbon phase diagram. Therefore, the proeutectoid phase for the given steel alloy is the phase that forms to the left of the eutectoid point, which is Ferrite (α-phase).

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Most popular questions from this chapter

An intermetallic compound is found in the goldtitanium system that has a composition of \(58.0\) wt \(\%\) Au-42.0 wt \(\%\) Ti. Specify the formula for this compound.

For a lead-tin alloy of composition \(80 \mathrm{wt} \% \mathrm{Sn}-\) \(20 \mathrm{wt} \% \mathrm{~Pb}\) and at \(180^{\circ} \mathrm{C}\left(355^{\circ} \mathrm{F}\right)\), do the following: (a) Determine the mass fractions of the \(\alpha\) and \(\beta\) phases. (b) Determine the mass fractions of primary \(\beta\) and eutectic microconstituents. (c) Determine the mass fraction of eutectic \(\beta\).

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Compute the mass fractions of proeutectoid ferrite and pearlite that form in an iron-carbon alloy containing \(0.35 \mathrm{wt} \% \mathrm{C}\).

A hypothetical A-B alloy of composition 40 \(\mathrm{wt} \% \mathrm{~B}-60 \mathrm{wt} \% \mathrm{~A}\) at some temperature is found to consist of mass fractions of \(0.66\) and \(0.34\) for the \(\alpha\) and \(\beta\) phases, respectively. If the composition of the \(\alpha\) phase is \(13 \mathrm{wt} \%\) B-87 wt \(\% \mathrm{~A}\), what is the composition of the \(\beta\) phase?
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