Ferrite (α-iron, δ-iron; soft) Austenite (γ-iron; harder) Spheroidite Pearlite (88% ferrite, 12% cementite) Bainite Martensite Ledeburite (ferrite-cementite eutectic, 4.3% carbon) Cementite (iron carbide, Fe3C; hardest)
Carbon steel (≤2.1% carbon; low alloy) Stainless steel (+chromium) Maraging steel (+nickel) Alloy steel (hard) Tool steel (harder)
Cast iron (>2.1% carbon) Ductile iron Wrought iron (contains slag)