Precipitation behavior and kinetics in Nb-V-bearing low-carbon steel

Superior mechanical properties of microalloyed steels processed via a new technology based on austenite conditioning followed by warm deformation

“…Particle precipitation, TiC in the Ti-steel and NbC in the NbTi-steel, does happen during holding at 600 °C. This corresponds to earlier published results [13][14][15][16][17][18][19][20]; 2. Growth of TiC particles in the Ti-steel is occurring at a much faster rate than this of NbC particles in the NbTi-steel.…”

“…Two processing schedules were applied to each of two steels ( Figure 1): without holding after warm deformation or with holding. The processing involved:  austenitising at 1250 °C for 300 s, followed by cooling to 1100 °C at a cooling rate of 1 °Cs -1 ; this reheating procedure was used in accordance with the previous study on NbTi-steel [10] in order to compare the previous and current results;  first deformation at 1100 °C to 0.35 strain at 5 s -1 strain rate; this temperature was chosen to be well above Tnr for the studied steels, which is 900 °C and 975 °C for the Ti-and NbTi-steels, respectively [11];  second deformation at 975 °C to 0.50 strain at 5 s -1 strain rate, these parameters had to allow complete DRX in the Ti-steel and partial recrystallization in the NbTi-steel [12];  cooling to 675 °C at a cooling rate of 40 °Cs -1 ; this temperature was chosen to be below A1  750 °C for both steels, and the cooling rate had to assure retention of deformed microstructure after the second deformation and prevention of pearlite formation;  third deformation at 675 °C to 0.25 strain at 5 s -1 strain rate gave sufficient work hardening;  holding at 600 °C for 300 s was supposed to promote Nb precipitation in the NbTi-steel [13][14][15][16][17] and, possibly, facilitate the TiC precipitation in the Ti-steel [18][19][20]; to verify the effect of holding on microstructure and mechanical properties, a schedule without holding was also tested. General microstructure characterisation for the four studied conditions was carried out using optical and scanning electron microscopy.…”

Modeling of Precipitation Behavior of Complex Precipitates in Ferrite and Validation with Experiment

“…For convenience of discussion, the experimental results tested by Li et al in ref . were used to verify the present model.…”

“…In order to validate the predicted precipitation kinetic results of complex precipitate formed at 650 °C, the interfacial energy was set to 0.52 Jm −2 and was set to 0.8 times of . The calculated mean particle diameter and experimental measurements are plotted in Figure . It can be seen that they agree, especially at longer times.…”

Precipitation and Mechanical Property of V‐Alloyed Steel: Role of Cooling Rate

“…These nanosized particles with the NaCl‐type crystal structure have the Baker–Nutting (BN) or Nishiyama–Wassermann (NW) orientation relationship with the ferrite matrix . Previous studies reported that the chemical composition, size, morphology, and number density of precipitates were affected by cooling rate, reduction rate, transformation temperature, transformation time, and microalloying element content . In particular, low cooling rate or long transformation time under certain condition increases the number density of nanosized precipitates, which is beneficial for improving the mechanical properties of microalloyed steels.…”