Journal of Advanced Materials and Technologies

Journal of Advanced Materials and Technologies

Development of Nanostructured Bainitic Steel by Utilizing the Two Steps Austempering Heat Ttreatment

Authors
Milad Foughani
Alireza Kolahi
Mehdi Alizadeh
Yahya Palizdar
Materials and Energy Research Center (MERC), Department of Nanotechnology and Advanced Materials, Karaj, Iran.
10.30501/jamt.2637.70343
Abstract
Special mechanical properties of nano structure bainitic steel such as high tensile strength, hardness, toughness and low manufacturing cost have attracted considerable attention in the past few years. However, the main problem for this type of steels to be industrialized, long austempering process period which increases production costs. In this research, in order to accelerate the bainitic transformation, carbon concentration was decreased and two steps austempering process was employed to prevent the bainite laths thickening. Specimens were austenetized at 1000 ᵒC for 15 min and were kept in the salt bath between 1-12 hours at temperatures in the range of 250-300ᵒC in one step or two step bainite transformation. Standard metallography, XRD and scanning electron microscopy techniques were utilized for the microstructural characterization and the tensile and hardness test were employed for mechanical properties evaluation. The obtained results show that two steps austempering process and lower carbon concentration lead to lower austempering period as well as formation of more stable retained austenite which results in higher mechanical properties.
Keywords
Medium Carbon Steels
Nanostructure Bainite
Two Steps Austempering
Mechanical properties
  1. Bhadeshia, Harshad KDH. "High performance bainitic steels."Materials Science Forum. Vol. 500. Trans Tech Publications, 2005.
  2. Bhadeshia, H. K. D. H. "Nanostructured bainite."Proceedings of the Royal Society of London A: Mathematical, Physical and Engineering Sciences. Vol. 466. No. 2113. The Royal Society, 2010.
  3. Lee, Y. K., et al. "Effect of isothermal transformation temperature on amount of retained austenite and its thermal stability in a bainitic Fe–3% Si–0.45% C–X steel."Scripta Materialia47.12 (2002): 805-809.
  4. Arijitsahapodder, "Tempering of a Mixture of Bainite and Retained Austenite،" University of Cambridge, 2011.
  5. Wang, X. L., et al. "Multi-step isothermal bainitic transformation in medium-carbon steel."Scripta Materialia74 (2014): 56-59.
  6. C.Garcia-Mateo, F.Caballero, H.Bhadeshia, "Acceleration of Low-Temperature Bainite." ISIJ Int. 2003;43:1821-5.
  7. Hu, F., P. D. Hodgson, and K. M. Wu. "Acceleration of the super bainite transformation through a coarse austenite grain size."Materials letters122 (2014): 240-243.
  8. Li, H. Y., et al. "Bainitic transformation during the two-step quenching and partitioning process in a medium carbon steel containing silicon."Materials Science and Engineering: A527.23 (2010): 6255-6259.
  9. Garcia-Mateo, Carlos, F. G. Caballero, and H. K. D. H. Bhadeshia. "Development of hard bainite."ISIJ international43.8 (2003): 1238-1243.
  10. Bhadeshia, H. K. D. H. "Bainite in steels: transformation, microstructure and properties."London: The Institute of Materials, University of Cambridge(2001): 377-382.
  11. Zhang, M., et al. "Preparation of nanostructured bainite in medium-carbon alloysteel."Materials Science and Engineering: A568 (2013): 123-126.
  12.  msm.cam.ac.uk/map/steel/programs/mucg83.html
  13. STEEL, KEYTO. "Influence of Alloying Elements on Steel Microestructure."Key to Steel Web Site. Actualizada en septiembre del(2001).
Journal of Advanced Materials and Technologies
Volume 5, Issue 4
Winter 2016
Pages 11-17

  • Receive Date 11 January 2017
  • Revise Date 18 January 2017
  • Accept Date 20 January 2017