| In an attempt to investigate the stabilization of austenite and its effects on the mechanical properties of DP steel, the variation in the volume fraction of retained austenite and stress-strain curves were analysized in accordance with the variations in alloy composition, annealing temperature, cooling rate, prior structure and isothermal holding time below Ms temperature. The amount of retained austenite increased maximum 80% when 1% nickel was added, and more austenite was retained from martensite structure than from as hot-rolled structure. When specimens were isothermally treated below Ms temperature the amount of retained austenite was more than doubled. Stress-strain curves were analyzed according to the Hollomon and Crussard-Jaoul equations. Isothermal holding below Ms temperature resulted in the increases in 0.2% yield strength and elongation, decrease in tensile strength, and, particulary, larger work hardening rates in third stage compared to second stage. This peculiar work hardening behavior was interpreted as the result of deformation induced transformation of retained austenite which presents in larger amount in this specimen. |
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