Final answer:
To calculate the mass fraction of eutectoid ferrite in an iron-carbon alloy, you can use the lever rule. This involves determining the distances between phase boundaries on a phase diagram and using them in a formula. The mass fraction of eutectoid ferrite can then be used to calculate the mass fraction of carbon and iron.
Step-by-step explanation:
The mass fraction of eutectoid ferrite in an iron-carbon alloy can be calculated using the lever rule. The lever rule states that the fraction of a phase present in an alloy is equal to the distance of the phase boundary divided by the total distance between the two phase boundaries. In this case, the phase boundaries are the boundaries between eutectoid ferrite and austenite, and between eutectoid ferrite and cementite.
The mass fraction of eutectoid ferrite can be calculated using the following formula:
mass fraction of ferrite = (distance from eutectoid ferrite boundary) / (distance between eutectoid ferrite and austenite boundaries)
You will need to refer to the phase diagram to determine the distances. Once you have the mass fraction of eutectoid ferrite, you can calculate the mass fraction of carbon using the relationship between the two phases. For example, if eutectoid ferrite and cementite have a mass fraction ratio of 1:1, then the mass fraction of carbon would be equal to the mass fraction of ferrite. Finally, you can subtract the mass fraction of carbon from 1 to find the mass fraction of iron.