Intercritical annealing treatment of PHS2000 and study of its microstructure and properties

Dual-phase steel (also known as DP steel) is the most widely used ultra-high-strength steel in automobile covering parts and structural parts. Since the concept of automotive lightweight has been put forward and deepened, the development of higher strength grade DP steel and the study of its microstructure and properties are of great significance. In this paper, the Gleeble-3800 thermal simulation machine was used to investigate the phase transition characteristics of the PHS2000. Scanning electron microscopy (SEM) was used to study the evolution of the microstructure under different heat treatment conditions, and the mechanical properties of dual phase microstructure under different conditions were analyzed. The results show that the microstructure of PHS2000 remains martensite with a high volume fraction after intercritical annealing and becomes full martensite after a long time of holding. At the same time, the tensile strength increases, and the plasticity decreases with the increase of the intercritical annealing temperature.