Dynamic mechanical properties of high strength TRIP steel

Using Si-Mn dual-phase (DP) steel as a reference, the microstructural evolution and dynamic mechanical properties of Si-Mn transformation-induced plasticity steel (TRIP) steel at the 600 MPa level and TRIP steel offering the ultimate tensile strength (UTS) level up to 1000 MPa containing Al and Ni were investigated under high strain-rate deformation. It is found that the tensile strength increases with increasing strain rate and the fracture elongation increases due to adiabatic heating in the DP steel. In the TRIP steel, the tensile strength increases with increasing strain rate while the fracture elongation decreases at first and then increases. However, the ductility of the TRIP steel is relatively low at high strain rate since the gradual transformation effect of retained austenite is inhibited. The adiabatic heat produced during high strain-rate deformation is higher in the TRIP steel than in the DP steel, and it is suggested that this extra heat originates from the latent heat of martensitic transformation in the TRIP steel during dynamic deformation.