Effect of retained austenite phase on springback of cold-rolled TRIP steel sheets

We examined the effects of retained austenite phase on the springback of cold-rolled transformation-induced plasticity (TRIP) steel sheets through a series of V-bending tests. Prior to testing, the intercritically annealed TRIP steel sheets were heat-treated at different austempering temperatures (300, 350 and 400 °C) to obtain three specimens with different retained austenite phase fractions. s show that the amount of springback in TRIP steel decreased as the fraction of retained austenite phase increased. The amount of springback was reduced by about 30% when the fraction of retained austenite phase increased by 5%. When the area fractions of the retained austenite phase of TRIP steel were less than 3%, we observed micro-cracks in the near-surface points of a V-shaped specimen where compressive and tensile stresses were concentrated. The dependency of materialʹs direction upon springback was very weak in the V-bending test where no constraint such as a blank holder exists during testing.