Overall stress-strain relationship of cold rotted transformation induced plasticity multiphase steels

As a result of transformation induced plasticity, TRIP assisted steels possess favourable mechanical properties such as high strength, ductility and toughness. In the present work, the flow stress of a cold rolled TRIP multiphase steel has been calculated from the stress of individual constituent phases on the basis of a continuum model whereby the internal stress produced by the inhomogeneous distribution of plastic strain is considered. For the first time, account is taken of how the volume fraction of constituent phases changes with strain. A comparison of stress-strain curves determined from the model and experimentally derived stress-strain curves for an Si-Mn type TRIP800 steel gives satisfactory agreement. Variation of the strain hardening exponent of the TRIP steel with strain is also discussed.