EFFECT OF MICROSTRUCTURE ON TRANSFORMATION-INDUCED PLASTICITY OF SILICON-CONTAINING LOW-ALLOY STEEL

Fe-0.6C-1.5Si-0.8Mn steel was studied to determine the effect oil the microstructure on transformation-induced plasticity (TRIP) of silicon- containing low-alloy steel. A remarkable increase in elongation throug h TRIP can develop in the steel subjected to the following heat treatm ents: (1) austemper combined with subcritical annealing (SA Aus-T): su bcritical annealing at 993K followed by austempering at 673K and then light tempering (after austenitization at 1173K); (2) austemper couple d with interrupted quenching (IQ Aus-T): interrupted quenching at 533K followed by austempering at 673K and light tempering (after austeniti zation at 1173K). The SA Aus-T treatment produced the triple structure s of carbide-free upper bainite, retained austenite (gamma(R)), and fr ee ferrite. As a result of the IQ Aus-T treatment, the triple structur es of carbide-free upper bainite, gamma(R), and tempered martensite ap peared. The results are described and microstructural factors in TRIP are discussed. (C) Elsevier Science Inc., 1997.