Laves phase precipitation and its transformation kinetics in the ferritic stainless steel type AISI 441

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:528

Article

Sello, M. P.¹  Stumpf, W. E.¹ 

[1] Univ Pretoria, Dept Mat Sci & Met Engn, ZA-0002 Pretoria, South Africa

关键词: Fe2Nb;    Time-temperature-precipitation (TTP) diagram;    Johnson-Mehl-Avrami-Kolmogorov (JMAK);    Transformation kinetics;   

DOI  :  10.1016/j.msea.2010.09.090

来源: Elsevier

【 摘 要 】

Electrolytic extraction followed by XRD analysis of precipitates after isothermal annealing of an AISI 441 ferritic stainless steel between 600 and 850 degrees C produced the time-temperature-precipitation (TTP) diagram for the Fe2Nb-Laves phase. The UP diagram shows two classical C noses, the first one between 750 and 825 degrees C and the second one, estimated to be close to 650-675 degrees C. TEM analyses show two independent nucleation mechanisms, i.e. at about 600 degrees C nucleation takes place on dislocations but above 750 degrees C, grain boundary nucleation is dominant. The measured solvus temperature of 875 degrees C for Fe2Nb in this steel is 50 degrees C higher than predicted by Thermo-Calc (R). Kinetic modelling at 800 degrees C agreed well with the experimental results for a surface energy of 0.435J m(-2) and an initial particle center-to-center separation distance on grain boundaries of about 0.2 mu m. (c) 2010 Elsevier B.V. All rights reserved.

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