Thermoplasticity and Microstructure Evolution of Duplex Stainless Steel 0Cr25Ni7Mo4N Subjected to High-temperature Tensile Deformation
LU Chengzhuang1, LI Jingyuan1, GAO Zhijun2, ZHANG Tairan2, CHEN Yulai2, WANG Yide2
1 School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083; 2 Metallurgical Engineering Research Institute, University of Science and Technology Beijing, Beijing 100083
Abstract: The present work investigated the hot deformation behavior of two types of austenite-ferrite duplex stainless steels 0Cr25Ni7Mo4N, which differed in oxygen and nitrogen contents, via a hot tensile test within the temperature range of 1 000 ℃ to 1 200 ℃ and at the strain rate of 1 s-1. The microstructures and inclusions were determined by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed that the steel deoxidized by aluminum and ferrosilicon (i.e. steel with relatively low oxygen and nitrogen contents) performs favorable thermoplasticity, while the undeoxidized steel with more oxygen and nitrogen exhibits good thermoplasticity only at above 1 150 ℃. This indicated the hot working temperature should be controlled above 1 150 ℃. The softening mechanism during the hot working process is the recovery of ferrite and the dynamic recrystallization of austenite. It can be concluded that the reasons for the low thermoplasticity of high-O, N-content steel are: the decline of binding strength at phase boundary induced by the precipitated coarse oxide inclusions containing chromium; the inappropriate ratio of austenite and ferrite phase.
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2018, Vol. 32 
