Effect of Yttrium Addition on the Microstructure and Mechanical Properties of Cu-Rich Nano-phase Strengthened Ferritic Steel
- 114 Downloads
Due to the brittle problem of Cu-rich nano-phase strengthened ferritic steel (CNSFS) after air aging, the effect of Y addition in CNSFS was systemically investigated in the present work. The microstructure, tensile fracture morphology and oxide layer of the steels were surveyed by optical microscope and scanning electron microscope. Transmission electron microscope with the combination of energy-dispersive x-ray spectroscopy and selected area electron diffraction was used to analyze the morphology, size, number density, chemical compositions and crystal structure for nano-crystalline precipitates. Microstructural examinations of the nano-crystalline precipitates show that Cu-rich precipitates and Y compounds in the range of 2-10 and 50-100 nm, respectively, form in the Y-containing steel; meanwhile, the average size of nano-crystalline precipitates in Y-containing steel is larger, but the number density is lower, and the ferritic grains are refined. Furthermore, the tensile strength and ductility of Y-containing steel after air aging are improved, whereas the tensile strength is enhanced and the ductility decreased after vacuum aging. The drag effect of Y makes the oxide layer thinner and be compacted. Tensile properties of CNSFS after air aging are improved due to the refined grains, antioxidation and purification by the addition of Y.
Keywordsaging Cu-rich phase nano-phase precipitation-strengthened steel tensile fracture morphology yttrium
Natural Science Foundation of Hubei Province in China (2014CFB801) supports this work.
- 3.Y.R. Wen, Y.P. Li, A. Hirata, Y. Zhang, T. Fujita, T. Furuhara, C.T. Liu, A. Chiba, and M.W. Chen, Synergistic Alloying Effect on Microstructural Evolution and Mechanical Properties of Cu Precipitation Strengthened Ferritic Alloys Mechanical Properties of Cu Precipitation-Strengthened Ferritic Alloys, Acta Mater., 2013, 61, p 7726–7740CrossRefGoogle Scholar
- 15.H.B. Xu, H.Y. Liu, M. Zhao, J.Y. Lv, Y.H. Ji, and M.P. Ke, Improvement in Tensile Properties of Cu-Rich Nano-Phase Strengthened Ferritic Steel by Addition of Y, J. Iron Steel Res., 2017, 29, p 62–68Google Scholar
- 16.J.W. Fan, Q.Y. Liu, H.R. Hou, H.J. Chen, and H. Dong, The Strength of Ultra-fine Grained Ferrite Steel, Heat Treat. Met., 2003, 28, p 5–10Google Scholar
- 17.Q. Lin, B. Song, X.M. Guo, and M. Zhang, Effects of RE on Microalloying in Steel and Application Prospects, Chin. Rare Earths, 2001, 22, p 31–36Google Scholar
- 18.X.Y. Zhu, T. You, Q. Shi, Z. Yang, and Q. Lin, Effect of Cerium on Microalloying in Low Sulfur Nb-Ti-Bearing Steel, J. Rare Earth, 2005, 23, p 742–746Google Scholar
- 20.R. Robie, B. Hemingway, and J. Fisher, Thermodynamic properties of minerals and related substances at 298.15 K and 1 bar (105 pascals) pressure and at higher temperatures, U.S. Geological Survey Bulletin 1452, United States Government Printing Office, Washington, 1978, p 246Google Scholar