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Hypoeutectoid steels - strength vs P content The Fe-C system
Martensite (MAR) Quenching suppresses diffusion AUS ––> P rxn doesn't go! But something has to happen - a. too much carbon for FE b. AUS needs to change structure AUS ––> MAR (very fine structure)
Martensite (MAR) MAR is metastable…… C is trapped in wrong structure MAR comes from AUS AUS wants to exsolve C & change atom arrangement
Transformation to MAR is time independent ….but temperature dependent Martensite (MAR) Transformation to MAR is time independent ….but temperature dependent martensite start martensite finish
Martensite (MAR) TTT curves & MAR formation
Martensite (MAR) Very hard, very strong due to: solution hardening by xs carbon residual internal strain But……
Martensite (MAR) Toughness = ??
Hardenability Definitions - For steels: harden = make MAR hardenability = ability to make MAR
Review today's notes a. what is martensite b. why is martensite c. martensite properties Read text: pp 277-290; 302-314 Do problems in text: 9.55, 9.57, 10.14, 10.16