mat33hw10

mat33hw10 - o C, hold for 100 seconds, then slowly cool to...

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Mat. 33 Homework # 10 4/13/09 1) Bainite exists in steel microstructures after certain heat treatments. The formation of pearlite involves the diffusion of all atoms while bainite grows by a transformation mechanism involving displacement. Pearlite occurs at the eutectoid of the iron-carbon phase diagram and is two phased while bainite only has one phase. The cooling rate to form bainite is higher than the cooling rate to form pearlite. 2) A) 50% austenite and 50% bainite B) 50% austenite and 50% bainite C) 100% martensite D) 55% austenite and 45% bainite 3) A) Starting at 800 o C rapidly cool to 500 o C, hold for 100 seconds reheat to 600 o C for 900 seconds, quench to room temperature. B) Starting at room temperature heat to 600
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Unformatted text preview: o C, hold for 100 seconds, then slowly cool to room temperature, reheat to 100 o C, then rapidly quench to room temperature. 4) A) austenite and proeutectoid cementite B) austenite and bainite C) austenite and bainite (much more bainite) 5) A) The microstructure of tempered martensite consists of extremely small and uniformly dispersed cementite particles embedded within a continuous ferrite matrix. The microstructure of martensite can either be twinned or parallelogram. B) Martensite is much harder but more brittle then tempered martensite because it has enhanced ductility and toughness, the continuous ferrite phase is a big reason for this. 6)...
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mat33hw10 - o C, hold for 100 seconds, then slowly cool to...

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