Hypo vs. Hyper Eutectoid Steels: From Austenite to Pearlite and Proeutectoid Phase Step by Step

Welcome back to MechTalks2025!
In this lesson, we dive deep into one of the most important transformations in metallurgy — from austenite to pearlite — and explore how proeutectoid ferrite and cementite form in hypo- and hyper-eutectoid steels.

Through two fully solved problems, you’ll learn how to:

Identify the proeutectoid phase (ferrite or cementite) based on carbon composition

Apply the lever rule to calculate phase fractions in real steel systems

Determine the mass of pearlite, ferrite, and cementite after cooling below the eutectoid temperature

Visualize and sketch the final microstructure step by step

These concepts are essential for every mechanical or materials engineer who wants to connect phase diagrams to mechanical behavior — from hardness and ductility to strength and microstructural control in heat treatment.

🎓 Watch this video after completing:
1️⃣ Mastering Phase Diagrams: Lever Rule, Phase Fractions & Mechanical Strength
2️⃣ Eutectic Alloys in Action: Hypo, Hyper & Weight Fraction Calculations Explained
3️⃣ Eutectoid, Peritectic & Microstructure Magic: Ferrite, Pearlite, Austenite Explained

Each video builds your understanding step by step toward real engineering insight.

📍 Next Up: TTT Diagrams & Heat Treatment — Controlling Pearlite, Bainite & Martensite Formation

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