Abstract

WU, G-L; ZHANG, Y-J  and  WU, S-W. Characterization of hot deformation behaviour of Nb-Ti microalloyed high-strength steel. J. S. Afr. Inst. Min. Metall. [online]. 2019, vol.119, n.5, pp.503-508. ISSN 2411-9717.  http://dx.doi.org/10.17159/2411-9717/17/380/2019.

The hot deformation behaviour of Nb-Ti microalloyed high-strength steel was investigated. Hot compression tests were conducted in the temperature range 900 to 1100°C under strain rates of 0.1, 1, and 5 s^-1. Dynamic recrystallization (DRX) occurs as the main flow softening mechanism at high temperature and low strain rate. The hot deformation activation energy was calculated to be about 404 699 J/mol. The constitutive equation was developed to describe the relationship between peak stress, strain rate, and deformation temperature. The characteristics of DRX at different deformation conditions were extracted from the stress-strain curves using the work hardening parameter. The Cingara-McQueen equation was developed to predict the flow curves up to the peak strain. The processing maps were obtained on the basis of a dynamic materials model. The results predict an instability region in the temperature range 1010 to 1100°C when the strain rate exceeds 0.78 s^-1.

Keywords : flow stress; high-strength steel; constitutive model; material constants; processing map.

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