1. Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering Summary of Material Science Chapter 1: Science of Materials Chapter 2: Properties of Materials Chapter 3: Material Testing Chapter 4: Alloys of Materials Chapter 5: Plain Carbon Steels Chapter 6: Heat Treatment Chapter 7: Cast Iron Chapter 8: Plastics/Polymers Chapter 9: Composite Materials Chapter 10: Ceramics Chapter 11: Semiconductors & Diodes Chapter 12: Biomaterials Chapter 13: Electrochemistry

2. Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering Iron age ~ 2000BCAsia Steel ~ 1870BC Heat Iron ore (Fe 2 O 3 ) up in charcoal  Carbon combines with oxide to form CO 2 ( ) & Iron (0.2-0.8%C) At very high temperatures iron absorbs carbon, this causes iron to melt & reforms as cast iron (3-4.5%C) Cast iron is hard & brittle  pig iron If melted cast iron is stirred the carbon oxidises and wrought iron is formed (first type of steel, 0.2-1.5%C). Steel is not soft like iron or brittle like cast iron  just right! History of Steel

3. Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering IRON-CARBON (Fe-C) PHASE DIAGRAM Eutectic: 4.3% C –L   + Fe 3 C –(L  solid + solid) Eutectoid: 0.76% C –    + Fe 3 C –(solid  solid + solid) Hyper-eutectic Hypo-eutectic Hyper- eutectoid Hypo- eutectoid Cementite (Fe 3 C)

4. Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering Iron-Carbon Phase Diagram Pure iron: 3 solid phases –BCC (  –FCC Austenite (  ) –BCC ferrite (  ) SteelCast Iron

5. Eutectoid Composition Pearlite microstructure: Just below the eutectoid point Pearlite: α Ferrite (White) Cementite (Fe 3 C) Austenite (γ)

6. Hypo-eutectoid Composition Lower the Carbon content the more α-Ferrite formed

7. Hypereutectoid Composition Higher the Carbon content the more cementite (Fe 3 C) formed

8. Temperature/%C Content of Eutectoid Compositions Alloying Steel with more Elements Austenite Stabilising Elements

9. Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering THE EFFECT OF CARBON ON THE PROPERTIES OF PLAIN CARBON STEELS

10. Plain Carbon Steels Low carbon steels, up to 0.15% carbon. Their main property is ductility and they are used where cold forming is necessary. They are easily welded. Structural steels, 0.15 – 0.3% carbon. These are less easily cold formed, but they are stronger and can still be easily welded. They are used for girders, ship plates and containers for gases and liquids. Medium carbon steels, 0.3 – 0.6% carbon. These steels are usually hot forged and are likely to crack if welded. They have good strength and ductility and are used as; axels, crankshafts and connecting rods. High carbon steels, 0.6 – 0.8% carbon. The main property is hardness and wear resistance. They are shaped by hot forging and are used as springs, hammers, railway wheels and rails, and wire ropes. Tool steels, 0.8 – 1.2% carbon. In cast or normalized state, these steels have very low toughness due to a grain boundary network of iron carbide. Thermo-mechanical treatments allow these steels to be used as chisels, cutting tools, saws, punches, files and knives. THE EFFECT OF CARBON ON THE PROPERTIES OF PLAIN CARBON STEELS