Hot Ductility and Fracture Behavior of High-Ti Weathering Steel

The hot ductility behavior of high-Ti weathering steel is studied by high-temperature tensile testing in the temperature range of 650-1100 oC. The results reveal a ductility trough in high-Ti steel in the range of 650-962, 650-925, and 700-880 degrees C with minimum reduction in area (RA) of 22.21%, 36.53%, and 43.25% at 800 oC and different strain rates of 1.0 x 10(-3), 5.0 x 10(-3), and 1.0 x 10(-2) s(-1), respectively. A number of secondary cracks containing S, N, and Ti propagate along the grain boundary, and the obvious preferred orientation is found in the microstructure near the fracture at 800 degrees C. With the increase in strain rate, the value of RA is increased in the temperature range of 650-1050 oC, such that the probability of crack occurrence is decreased. RA does not increase with the increase in strain rate at 1100 degrees C and strain rate of 1.0 x 10(-2) s(-1). The underlying reason is that there is not adequate time for the material to recover or recrystallize with the increase in strain rate, resulting in material softening effect that is not completely reflected.