Precipitation behavior of a HSLA steel containing molybdenum, aluminum and trace amounts of titanium

The precipitation sequence in a HSLA steel containing 0.29% Mo, 0.065% Al and small amounts of titanium (≤ 50 ppm) has been studied. Samples previously deformed at various strain rates at 8750C were characterized by analytical electron microscopy. The precipitates are classified according to chemical composition and size which allowed evolution of precipitate populations as a function of strain rate to be followed. Small amounts of titanium, inadvertently introduced during steelmaking, modified considerably the expected precipitation sequence. Hence, AlN dynamic precipitation was not observed but rather a Mo-rich compound (probably a carbide) was found to precipitate during deformation. This dynamic precipitation accounts for the additional retardation of recrystallization at intermediate strain rates. These results are discussed with respect to the interaction between recrystallization, precipitation and effects of strain rate on precipitation kinetics