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利用共聚焦激光扫描显微镜原位观察节镍型奥氏体不锈钢中奥氏体(γ)向高温铁素体(δ)转变的全过程。结果表明,未腐蚀试样在1150℃到1250℃区间加热、保温易于形成孪晶;在1250～1350℃加热、保温过程中,δ相的形核和长大显著,形核位置主要为γ片和CaO-SiO2-Al2O3-MgO系复合夹杂物处;在1350～1450℃区间为δ相晶界的迁移。腐蚀试样在室温至1450℃区间加热和保温过程中,原室温组织中δr相的形态、分布变化不大,高温下新形成的δe相与原δr相无明显联系。利用晶粒长大动力学理论和Creq/Nieq比值分析了节镍型奥氏体不锈钢中δ相晶界迁移现象和凝固模式,并探讨了凝固模式对升温过程的指导作用。
The whole process of austenite (γ) transformation into high temperature ferrite (δ) in nodular nickel austenitic stainless steel was observed in situ by confocal laser scanning microscope. The results show that the non-corrosive sample is heated in the range of 1150 ℃ to 1250 ℃, and the twinning is easy to form during the heat preservation. The nucleation and growth of δ phase are remarkable during heating and holding at 1250-1350 ℃. And CaO-SiO2-Al2O3-MgO composite inclusions; in the 1350 ~ 1450 ℃ interval δ-phase grain boundary migration. In the process of heating and holding the corrosion samples from room temperature to 1450 ℃, the morphology and distribution ofδr phase did not change much in the original room temperature. There was no obvious relationship between δe phase and δr phase at high temperature. The δ-phase grain boundary migration and solidification mode in nodular nickel-austenitic stainless steel were analyzed by using the theory of grain growth kinetics and Creq / Nieq ratio, and the guiding role of solidification mode to temperature rising process was also discussed.