MATS 3011 Lecture Notes - Pearlite, Saurer, Cyc
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Different microstructures as function of heat treatment for same composition. Even if you"re in different parts of the pearlite region, you"ll have different microstructure. Different temperatures --> higher t has more diffusion --> coarse pearlite. Lower t --> less diffusion --> fine pearlite. If go even lower t, get bainite (same composition as pearlite, but different microstructure) Phase fraction of alpha and fe 3c and composition remain same as that of pearlite and bainite. If take austenite and just cool it (w/o forming pearlite and bainite), goes really fast from austenite to martensite why"s the transformation so fast? (even w/ lower t --> limited diffusion) --> still under investigation/research. -> it forms a new phase as shown. Martensite: forms due to diffusionless transformation of gamma-fe gamma-fe (fcc) -----------> martensite (also fe) (bct: body central tetragonal) Martensite phase is a non-equilibrium phase (that"s why we don"t see it on phase diagram)