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。
Transformation process from austenite（γ）to high-temperature delta ferrite（δ）in a nickel-saving austenitic stainless steel was in situ observed by using confocal laser scanning microscope.The etched sample as well as the polished sample was heating and holding at different temperatures from room temperature to 1450 ℃.The results show that the polished sample heating from 1150 ℃ to 1250 ℃ is priority to form twins.The nucleation and growth of δ phase are observed,and the locations of nucleation are at the γ plate and the CaO-SiO2-Al2O3-MgO complex inclusion during heating and holding from 1250 ℃ to 1350 ℃.The grain boundary migration phenomenon of δ phase was analyzed by using the dynamics theory.When heating and holding from room temperature to 1450 ℃,no significant change for the shape and distribution of original δr phase is observed in the etched sample,and the δe phase generated at high temperature has no relation with the original δr phase.The Creq/Nieq ratio is used to discuss the solidification and grain boundary migration phenomenon of the nickel-saving stainless steel.
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