Microstructural Evolution and Mechanical Properties of Modified 9%Cr-1%Mo Steel upon Isothermal Heat-Treatment


Article Preview

The evolution of microstructure and its effects on the mechanical properties of modified 9%Cr-1%Mo steel during heat-treating at 1050°C for 15 min and then isothermal heat treatment at 380~760°C with subsequent air-cooling have been investigated. For the microstructural and mechanical property analyses, OM, SEM, EDS, XRD, hardness and impact tests were used. In accordance with the severity of the heat-treatment, the microstructure evolved from the untransformed martensite to the partially transformed dual phases of martensite and ferrite, and then fully transformed to ferrite. Impact values at ambient temperature for specimens isothermally heat-treated at 320 - 380°C, predominantly at about 350°C were lower than others’ with similar martensitic structure. The partially transformed specimens with dual phases of martensite and ferrite also showed lower impact values than samples with untransformed with martensitic, and transformed with ferritic structures.



Materials Science Forum (Volumes 475-479)

Main Theme:

Edited by:

Z.Y. Zhong, H. Saka, T.H. Kim, E.A. Holm, Y.F. Han and X.S. Xie




S. K. Hur et al., "Microstructural Evolution and Mechanical Properties of Modified 9%Cr-1%Mo Steel upon Isothermal Heat-Treatment", Materials Science Forum, Vols. 475-479, pp. 81-84, 2005

Online since:

January 2005




[1] The T91/P91 Book, Vallourec & Mannesmann Tubes, (1999).

[2] Heat Resistant Materials, ASM International, (1997).

[3] Ferritic Heat Resistant Steels, edit. by Ohta Sadao, Chijin Syokan, (1995).

[4] C.L. Briant. and S.K. Banerji: Metall. Trans. A, Vol. 12A Feb, 1981, p.310.

[5] Embrittlement, Properties and Selection: Iron, Steels, and High Performance Alloys, ASM International. Edited by J.R. Davis , Davis &Associate, 1990, p.689.

[6] J.A. Peter et al.: Acta Metall. Vol. 39, 1989, p.675.

[7] K.T. Park and H. -J. Kwon, Met. Mater. -Int., Vol. 7, No. 2, 2001, p.95.

[8] Y. S. Lee and S. H. Ryu: Proc. of the 14th Conf. on Mechanical Behavior of Materials, Seoul, Korea, Nov., 11, 2000, p.93.