冷却速率对奥氏体不锈钢凝固过程影响的原位观察研究.pdfVIP

冷却速率对奥氏体不锈钢凝固过程影响的原位观察研究 黄福祥 王新华 王万军 1 （北京科技大学冶金与生态工程学院，北京 100083 ） 摘 要 通过采用激光共聚焦扫描显微镜对 AISI304 奥氏体不锈钢的凝固过程进行了原位动态观察研究，发 现当冷却速率为 0.05 K/s 时，奥氏体不锈钢以胞状晶方式凝固，其凝固模式为 FA 模式，即 δ铁素体相先从 液相中形核并长大，γ相在 1448.9 ℃时通过与液相发生包晶反应（L+δ→γ）在 δ铁素体相界形成，当温度降 到 1431.3 ℃时液相消失，δ铁素体相通过固态相变转变为 γ相，富 Cr 贫 Ni 的残留铁素体位于胞状晶之间。 当冷却速率为 3.0 K/s 时，奥氏体不锈钢以枝晶方式生长，冷却到 1346.4 ℃时包晶反应在液相与 δ铁素体相 界之间进行，其残留铁素体位于枝晶干，与冷却速率为 0.05 K/s 时相比，其残留铁素体的数量增多，残留铁 素体富 Cr 贫 Ni 的程度减轻。 关键词 奥氏体不锈钢 凝固 残留铁素体 激光共聚焦扫描显微镜 Effect of Cooling Rate on Solidification Process of Austenitic Stainless Steel by In-situ Observation Huang Fuxiang Wang Xinhua Wang Wanjun (School of Metallurgical and Ecological Engineering, University of Science and Technology, Beijing, 100083) Abstract The solidification process of austenitic stainless steel during cooling at a rate of 0.05 K·s-1and 3.0 K·s-1 have been observed in situ by using confocal laser scanning microscope. The results show that the solidification mode of austenitic stainless steel belong to FA mode when the cooling rate is 0.05 K/s, that’s to say the δ ferrite appeared firstly in the liquid steel, then the γ phase precipitated prior at δ-grain boundary at 1448.9 ℃, the liquid steel disappeared at 1431.3 ℃, and then the δ ferrite transformed to γ phase by solid diffusion, the retained ferrite which enriched in Cr and depleted in Ni located between the cellular dendrites. When the cooling rate is 3.0 K/s, the solidification interface morphology becomes dendrite, the retained ferrite located in the dendrite arm, compared to 0.05 K/s, the degree of enriched in Cr and depleted in Ni in the residual ferrite decreased but the amount of them