IN SITU OBSERVATION OF GROWTH BEHAVIOR AND MORPHOLOGY OF DELTA-FERRITE AS FUNCTION OF SOLIDIFICATION RATE IN AN AISI304 STAINLESS STEEL

作     者：G.F.Liang C.Q.Wan J.C.Wu G.M.Zhu Y.Yu Y.Fang 

作者机构：Advanced Technology InstituteTechnology Center of BaosteelShanghai 201900China Department of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200030China 

出 版 物：《Acta Metallurgica Sinica(English Letters)》 (金属学报(英文版))

年 卷 期：2006年第19卷第6期

页      面：441-448页

核心收录：

学科分类：08[工学] 080502[工学-材料学] 0805[工学-材料科学与工程（可授工学、理学学位）] 

基　　金：This work was supported by the China Postdoctoral Science Foundation (No. 20060390150) 

主　　题：stainless steel confocal scanning laser microscopy δ-ferrite in situ observation solidification 

摘      要：It was presented the in situ observation of growth behavior and morphology of delta-ferrite as a function of solidification rate in an AISI304 stainless steel. The specimens have been solidified and observed using confocal scanning laser microscopy (CSLM). The δ-phase always appears like cells on the sample surface when critical supercooling occurs, during which the L→δ transformation starts. The solid-liquid (S-L) interface is found to be finger shaped and has no faceted shape. γ phase appears among δ grains due to partitioning of Ni into the melt during solidification, when solidification rate is higher. The mergence of observed δ cells is possible for the steel sample cooled at 7.5℃/min. The formation of dendrites can be observed on the free surface of the steel sample cooled at 150℃/min. The size of solidified delta grains decreases from 120 to 20-80μm, and the volume fraction of solidified austenite increases with increase in solidification rate from 7.5 to 150℃/min. The relation between the tip radius of δ cell and its growth rate is deduced, and the results agree with the experimental values.