Effects of Pre-Strain and Tempering on Mechanical Properties in High-Strength Martensitic Steels

Abstract:

Effects of pre-strain and tempering on mechanical properties in high-strength martensitic steels were investigated. In this study, strain tempering (ST) and quenching and tempering (QT) martensitic steels were prepared, and their mechanical properties were studied. In the tensile tests at the deformation temperatures between 296 and 573 K, the ST sample increased both of tensile strength (TS) and uniform elongation (U.El) from 473 to 523 K whereas the QT sample increased U.El with little change of TS. From the in situ neutron diffraction experiments, stress partitioning to the bcc phase increased with an increase in the deformation temperature from 296 to 523 K. The difference of phase stress between the bcc and cementite phases decreased with increasing the temperature because of a decrease in the cementite strength. In the ST sample, Pre-straining of 0.5% increased YS at 296 K with slight work hardening. The initial value of dislocation density (ρ) decreased at 523 K but ρ increased significantly after yielding, leading to better combination of TS and U.El. The combinations of pre-strain, tempering, and deformation temperatures have changed ρ before deformation and the increase of ρ after yielding of the martensitic steels.

• Periodical: Materials Science Forum (Volume 1105)
• Pages: 129-133
• DOI: https://doi.org/10.4028/p-sX7iEQ
• Online since: November 2023
• Authors: Noriyuki Tsuchida*, Rintaro Ueji, Wu Gong, Takuro Kawasaki, Stefanus Harjo
• Keywords: Martensitie, Mechanical Properties, Neutron Diffraction Experiments, Pre-Strain, Tempering

References

[1] H. Muir and M. Cohen, The elastic limit and yield behavior of hardened steels, Trans. Amer. Soc. Metals, 47 (1954) 380–407.

[2] S. Harjo, T. Kawasaki, Y. Tomota, W. Gong, K. Aizawa, G. Tichy, Z. Shi and T. Ungár, Work hardening, dislocation structure, and load partitioning in lath-martensite determined by in situ neutron diffraction line profile analysis, Metall. Mater. Trans. A, 48 (2017) 4080–4092.

DOI: 10.1007/s11661-017-4172-0

[3] T. Watanabe, A. Fukui, C. Asada, Effect of strain aging on the mechanical properties of low carbon martensite steel, Trans. JSSE, 15 (1970) 29–36.

DOI: 10.5346/trbane.1970.29

[4] D.V. Wilson, Effects of plastic deformation on carbode precipitation in steel, Acta Metall., 5 (1957) 293–302.

[5] N. Tsuchida, R. Ueji, W. Gong, T. Kawasaki, S. Harjo, Stress partitioning between bcc and cementite phases discussed from phase stress and dislocation density in martensite steels, Scripta Mater., 222 (2023), 115002.

DOI: 10.1016/j.scriptamat.2022.115002

[6] T. Ungár, J. Gubicza, G. Ribarik, A. Borbely, Crystallite size distribution and dislocation structure determined by diffraction profile analysis: principles and practical application to cubic and hexagonal crystals, J. Appl. Crystallogr., 34 (2001) 298–310.

DOI: 10.1107/s0021889801003715

[7] M. Umemoto, Y. Todaka, T. Takahashi, P. Li, R. Tokumiya and K. Tsuchiya, Characterization of bulk cementite produced by mechanical alloying and spark plasma sintering, J. Metastab. Nanocryst. Mater., 15-16 (2003) 607–614.

DOI: 10.4028/www.scientific.net/jmnm.15-16.607

[8] H. Mecking and U.F. Kocks, Kinetics of flow and strain-hardening, Acta Metall., 29 (1981) 1865–1875.

DOI: 10.1016/0001-6160(81)90112-7