SAF2507SDSS热冲压成形σ相析出行为研究

Study on precipitation behavior of σ phase in hot stamping forming for SAF2507SDSS

采用1600 t XPS型液压压力机和成形模具对SAF2507SDSS板材进行850～1100℃的热冲压成形,使用光学显微镜、扫描电镜和X射线能谱仪并结合JMatPro软件的模拟计算,研究了SAF2507SDSS热冲压成形σ相的析出规律和热冲压成形不同阶段的时间和冷却速率对σ相的影响。结果表明：随着热冲压成形温度的升高,σ相在δ/γ相界处形核并朝着δ相区域生长,含量先增多后减少,σ相的析出机理为δ→σ＋γ2,950℃是σ相敏感析出温度,1050℃是σ相稳定存在的温度上限;由于热冲压成形移动、形变和保压阶段的冷却速率均大于σ相临界析出的冷却速率,并且移动、形变和保压阶段的时间均小于σ相临界析出孕育时间,而σ相形核析出只发生在保温阶段,因此,热冲压成形对σ相形核析出无影响。

SAF2507 SDSS plates were subjected to hot stamping forming between 850 ℃ to 1100 ℃ by 1600 t XPS hydraulic press and forming die,and the precipitation regularity of σ phase in hot stamping forming for SAF2507 SDSS and the influences of time and cooling rate on σ phase in different stages of hot stamping forming were studied by optical microscope,scanning electron microscope,X-ray energy dispersive spectrometer and JMatPro software. The results show that with the increasing of temperature in hot stamping forming,σphase nucleates at the δ/γ phase boundary and grows towards the δ phase region,and the contents of σ phase increase first and then decrease. Furthermore,the precipitation mechanism of σ phase is δ→σ ＋ γ2,the most of sensitive precipitation temperature of σ phase is950 ℃,and the stable temperature limit of σ phase is 1050 ℃. Because the cooling rate in the hot stamping forming movement,deformation,and holding pressure phases are all greater than the critical precipitation cooling rate of σ phase,the time of movement,deformation and holding pressure phases are all less than the σ phase incubating time,and the nucleation of σ phase occurs only in the heat preservation stage. Therefore,the hot stamping forming has no effect on the σ phase.