Influence of isothermal aging onσprecipitation in super duplex stainless steel

Xiao-feng Wang~(1)),Wei-qing Chen~(1)),and Hong-guang Zheng~(2)) 1) School of Metallurgical and Ecological Engineering,University of Science and Technology Beijing,Beijing 100083,China 2) Technology Center for Stainless Steel,Baosteel Research Institute,Baoshan Iron and Steel Co.Ltd.,Shanghai 200431,China

摘 要：<正>The time-temperature-transformation（TTT） curve of the 00Cr25Ni7Mo4N duplex stainless steel was obtained with a Formastor -digital thermal dilatometer,and the influence of isothermal aging onσprecipitation was studied by metallographic observation,X-ray diffraction（XRD）,and transmission electron microscopy（TEM）.The results show that the decomposition of ferrite phase is accompanied by the formation ofσphase at 750-1000℃,especially in the range of 800-900℃.The longer the aging time,the higher the amount ofσprecipitation. The area fraction of various phases remains at a certain value upon the completion of ferrite deformation.The temperature of 850℃is the most sensitive transaction temperature,the incubation time for the formation ofσprecipitation is less than 1 min,and aging for 20 min leads to the complete transformation of ferrite.Theσphase is formed preferentially at theα/α/γjunction,and then grows along theα/αboundary in the matrix.

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