Flow Behaviour of Modified 9Cr–1Mo Steel at Elevated Temperatures

  • V. Shiva
  • Sunil Goyal
  • R. Sandhya
  • K. Laha
  • A. K. Bhaduri
Technical Paper


In this investigation, the flow behaviour of modified 9Cr–1Mo steel at elevated temperatures is reported. To understand the flow behaviour of the steel, tensile tests were performed at nominal strain rate of 3 × 10−3 s−1 and temperatures in the range of 300–823 K. The yield strength and ultimate tensile strength were found to decrease with increase in temperature with a plateau in a intermediate temperature regime (523–673 K). Serrations were also observed in the tensile curve at intermediate temperatures which caused plateau/peak in tensile behaviour of material and was a typical manifestation of dynamic strain ageing. An attempt was made to represent the flow behaviour of the material using different constitutive equations viz., Hollomon, Ludwik, Swift, Ludwigson and Voce. It was observed that the Voce equation could describe the experimental flow curve at different temperatures quite well. Instantaneous work hardening rate with respect to flow stress exhibited two stages of hardening especially at relatively lower temperatures.


Modified 9Cr–1Mo steel Tensile behaviour Yield strength Dynamic strain ageing Constitutive equations 

List of symbols


True stress


True strain


Pre strain


Pre stress

\({\text{K}}_{\text{H}} ,\,{\text{K}}_{\text{L}} ,\,{\text{K}}_{\text{S}} ,\,{\text{K}}_{1}\)

Strength coefficient of Hollomon, Ludwik, Swift and Ludwigson equations respectively

\({\text{n}}_{\text{H}} ,\,{\text{n}}_{\text{L}} ,\,{\text{n}}_{\text{S}} ,\,{\text{n}}_{1}\)

Strain hardening exponent of Hollomon, Ludwik, Swift and Ludwigson equations respectively


Saturation stress


Initial stress



The authors express their deep sense of gratitude to Dr. G. Amarendra, Director, Metallurgy and Materials Group, IGCAR for keen interest in this work and encouragement. The authors are thankful to Ms. S. Panneer Selvi for help during experiments. Authors would like to thank Mr. D. P. Rao Palaparti for the fruitful technical discussion.


  1. 1.
    Sikka V K, Ferritic Alloys for Use in Nuclear Energy Technologies, TMS-AIME, Warrendale, Pa (1984), p 317.Google Scholar
  2. 2.
    Mannan S L, Chetal S C, Raj B, and Bhoje S B, Trans Indian Inst Met 56 (2003) 155.Google Scholar
  3. 3.
    Laha K, Chandravathi K S, Parameswaran P, Bhanu Sankara Rao K, and Mannan S L, Metall Mater Trans A 38A (2007) 58.CrossRefGoogle Scholar
  4. 4.
    Vanaja J, Laha K, Shiju S, Nandagopal M, Panneer Selvi S, Mathew M D, Jayakumar T, and Rajendra Kumar E, J Nucl Mater 424 (2012) 116.CrossRefGoogle Scholar
  5. 5.
    Girish Shastry C, Mathew M D, Bhanu Sankara Rao K, and Mannan S L, Int J Pres Ves Piping 81 (2004) 297.CrossRefGoogle Scholar
  6. 6.
    Mishra N S, Mishra S, and Ramaswamy V, Metall Trans A 20 (1989) 2819.CrossRefGoogle Scholar
  7. 7.
    Lavakumar A, Murthy Ch V S, Satyanarayana D V V, and Eswara Prasad N, Int J Sci Eng Res 4 (8) (2013) 1914.Google Scholar
  8. 8.
    Ankamma K, Satyanarayana D V V, Sarkar R, Reddy G C M, Komaraiah M, and Eswara Prasad N, Mater Sci Technol 27 (8) (2011) 1333.CrossRefGoogle Scholar
  9. 9.
    Satyanarayana D V V, Malakondaiah G, and Sarma D S, Mater Sci Eng A 452–453 (2007) 244.CrossRefGoogle Scholar
  10. 10.
    Markandeya R, Nagarjuna S, Satyanarayana D V V, Sarma D S, Mater Sci Eng A 428 (2006) 233.CrossRefGoogle Scholar
  11. 11.
    Hollomon J H, Trans AIME 162 (1945) 268.Google Scholar
  12. 12.
    Ludwik P, Verlag Von Julius, Springer, New York (1909), p 32.Google Scholar
  13. 13.
    Swift H W, J Mech Phys Solids 1 (1952) 1.CrossRefGoogle Scholar
  14. 14.
    Ludwigson D C, Metall Trans 2 (1971) 2825.CrossRefGoogle Scholar
  15. 15.
    Voce E, J Inst Met 74 (1948) 537.Google Scholar
  16. 16.
    Voce E, Metallurgia 51 (1955) 219.Google Scholar
  17. 17.
    Rodriguez P, Bull Mater Sci 6 (4) (1984) 653.CrossRefGoogle Scholar
  18. 18.
    Rao Palaparti D P, Chodhary B K, Issac Samuel E, Srinivasan V S, and Mathew M D, Mater Sci Eng A 538 (2012) 110CrossRefGoogle Scholar
  19. 19.
    Choudhary B K, Mater Sci Eng A 564 (2013) 303.CrossRefGoogle Scholar
  20. 20.
    Choudhary B K, Rao Palaparti D P, and Isaac Samuel E, Metall Mater Trans A 44 (2013) 212.CrossRefGoogle Scholar
  21. 21.
    Isaac Samuel E, and Choudhary B K, Mater Sci Eng A 528 (2011) 7827.CrossRefGoogle Scholar

Copyright information

© The Indian Institute of Metals - IIM 2017

Authors and Affiliations

  1. 1.Indira Gandhi Centre for Atomic ResearchHBNIKalpakkamIndia

Personalised recommendations