Evolution of Microstructure and Mechanical Properties in Dual-Phase Steel Containing Ce and Nb

In the present work, a method of combining rare-earth nano-oxide cerium(IV) oxide (CeO2) and metal element niobium (Nb) was investigated. The effects of this method on the welding performance of DP780 dual-phase steel joints were examined. The microstructure and mechanical properties of DP780 were systematically investigated by scanning electron microscopy and energy-dispersive x-ray spectroscopy. Moreover, the fracture states of the joint with different CeO2 and Nb contents were simulated under the same conditions. The results showed that the best overall performance was achieved with 0.35% CeO2 and 0.13% Nb at an annealing temperature of 527 degrees C and an impact temperature of - 40 degrees C. The impact energy increased by 3.435 J, the tensile strength increased by 344.8 MPa, and the elongation after fracture was maintained at a high level with lower yield strength. The grain boundary size was reduced by 1.8605 mu m, and the overall maximum deformation of the weldment was reduced by 0.03913 mm.