Fe–C microstructures — identify the incorrect statement Which of the following statements about steel microstructures is WRONG?

Introduction / Context:
Understanding the constituents and proportions in steel microstructures is crucial for predicting properties and selecting heat treatments. Pearlite, ferrite, and cementite appear in characteristic forms and ratios depending on carbon content and cooling rate.

Given Data / Assumptions:

• Equilibrium or near-equilibrium cooling of plain carbon steels.
• Pearlite considered at eutectoid composition.
• Qualitative identification of cementite morphology and proeutectoid phases.

Concept / Approach:
Pearlite at the eutectoid composition consists of approximately 87% ferrite and 13% cementite by weight (sometimes quoted as 88/12). Therefore, any statement reversing these percentages is incorrect. As carbon content increases, the fraction of cementite in the overall microstructure rises. At 0.8% C, steel transforms fully to pearlite under slow cooling. Cementite can appear as lamellae in pearlite, as proeutectoid networks (in hypereutectoid steels), or as spheroids after spheroidising — in which case it may appear as rounded particles.

Step-by-Step Solution:

Verification / Alternative check:
Fe–Fe3C diagram and textbook micrographs corroborate pearlite fractions and morphologies.

Why Other Options Are Wrong (brief per option):

• (a) True for eutectoid steel at slow cooling.
• (b) True: higher carbon increases overall cementite fraction.
• (d) Can be true after spheroidising; in pearlite it is lamellar, but the statement does not specify condition.
• (e) True: ferrite proeutectoid for hypoeutectoid; cementite for hypereutectoid.

Common Pitfalls:
Reversing ferrite/cementite percentages; assuming “round cementite” exists in all conditions (it is specific to spheroidised structures).

Final Answer: