期刊
出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2017.02.057
关键词
Aging; Microstructure; Mechanical properties
类别
资金
- National Natural Science Foundation of China [50775107]
- China Petrochemical Corporation [315007]
- innovation program for graduate students in JiangSu Province of China [KYLX15_0800]
The centrifugally cast 20Cr32Ni1Nb stainless steel aged at 950 degrees C from 200 h up to 5000 h was investigated on the mechanical properties and microstructural evolution using post-aged tensile tests, post-aged Charpy impact tests, Optical microscopy (OM) observations, and field emission-scanning electron microscopy (FE-SEM) examinations. Experimental results indicate that the as-cast microstructure of the steel typically consists of a supersaturated solid solution of austenite matrix with a network of interdendritic primary carbides (NbC and M23C6). During aging process, the growth and coarsening of NbC carbides and M23C6 carbides as well as the transformation of NbC carbide into G phase take place. Meanwhile, the transformation of NbC into G phase releases C into the matrix during aging exposure. This released C tends to combine with Cr, and forms M23C6 at the dendrite boundaries. Compared with a continuous reduction of the elongation in the whole aging period, the strength parameters (sigma(ult) and sigma(ys)) exhibit an initial increase followed by a continuous decrease with the aging time prolonged from 1000 h to 5000 h. Additionally, the variation of Charpy impact absorbed energy is relatively complex during aging process. The microstructural evolution during long-term aging process is consistent with the variation of mechanical properties.
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