Texture and physical Properties of Dual-Phase steels
1
2
H. Klein, A. Wetzel, M. Masimov and T. Lippmann
GZG, Dept. of Crystallography, Univ. of Göttingen, Goldschmidtstr.1, 37077 Göttingen, Germany
1Salzgittter Mannesmann Forschung, Eisenhüttenstr.99, 38239 Salzgitter, Germany
2GKSS Research Center, Max-Planck-Str.1, 21502 Geesthacht, Germany
Dual-phase steels very sensitively change their texture and with it their anisotropic properties after
heat treatment. A cold rolled dual-phase steel was annealed at 780°C and 900°C and quenched under
different conditions. From the different samples textures were measured using high-energy
synchrotron radiation and conventional X-rays in order to compare the differences between these
methods on the basis of the calculation of anisotropic properties [4].
Texture measurement with high-energy-synchrotron radiation was carried out at the GKSS materials
science beam-line HARWI II at DESY, Hamburg, Germany. A beam-energy of ~100keV was chosen
and a beam cross section of 1mm x 1mm. The diffracted intensity was recorded by a mar345 area
detector. The synchrotron texture measurements were carried in the conventional step scan mode in a
range of the orientation angle ω: -80° ≤ ω ≤+80° in steps of ∆ω=1°, the recording-time was 2sec per 2dimensional image [1]. CoKα radiation was used for the texture measurements using conventional Xrays. With a Seifert PTS goniometer incomplete pole figures were measured in the ranges: 0° ≤ α ≤
70° with ∆α=5° and 0° ≤ β ≤ 360° in steps ∆β=3.6°. Three pole figures of the bcc phase were
measured: (110), (200) and (211). To get a comparable information to the synchrotron method a
special sample preparation was used: the sandwich technique. This technique allows the measurement
of the global texture because it uses a texture measurement of the transverse plane of a
sample[2].From the data of the diffraction experiments the orientation distribution function was
calculated in order to compare the different measurement methods and different treatments. The
orientation distribution function was calculated on the basis of the harmonic method after Bunge[3].
Fig.1 shows three Orientation distributions in ϕ2=45°-sections of the dual-phase steel in different
stages. The textures in Fig.1 are calculated from conventional X-ray measurements. In fig.1a the
typical cold rolled texture of bcc iron is to be seen. After annealing at 780°C and fast quenched to
room temperature the texture become weaker (fig.1b), it is very weak after heating up to 900°C and a
slow cooling down. Fig.2 shows the texture of the same samples, but measured using high-energy
synchrotron radiation. The level lines in fig. 1 and fig. 2 are comparable. One can observe, that the
textures become weaker, because with hard X-rays the real global texture is measured, in contrast to
the conventional X-ray measurements.
φ1
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Fig.1: Orientation Distribution Function in ϕ2=45°-sections of a dual-phase steel: a) cold rolled, b)
annealed at 780°C and fast quenched , c) annealed at 900°C and slowly cooled down. Measured with
conventional X-rays.
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φ1
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Fig.2: Orientation Distribution Function in ϕ2=45° sections of a dual-phase steel: a) cold rolled, b)
annealed at 780°C and fast quenched , c) annealed at 900°C and slowly cooled down. Measured with
high-energy synchrotron radiation.
From Orientation Distribution Functions the anisotropic Young’s modulus was calculated. Fig.3
shows the Young’s modulus as a function of the angle from rolling to transverse direction for different
annealing and cooling strategies. Calculations of anisotropic properties on the basis of texture
measurements using high-energy synchrotron radiation are very close to calculations on the basis of
global texture measurements with conventional X-rays. Because of the high penetration depth of the
synchrotron radiation a larger diffracted volume can be measured. This leads to a better information
about the global texture and thus about the anisotropic properties.
Fig.3: Anisotropic Young’s modulus of a dual-phase steel treated under different conditions –cold
rolled and annealed at 900°C and slowly cooled- and different measurement methods of textures:
High-energy synchrotron radiation and conventional X-rays.
References
[1] H.J. Bunge, H.Klein, L. Wcislak, U. Garbe, W. Weiß and J.R. Schneider, Textures and
Microstructures, 35, 253 (2003).
[2] H. Klein, C. Heubeck and H.J. Bunge, Mat. Sci. Forum, 157-162, 1423 (1994)
[3] H. J. Bunge, Texture Analysis in Material Science, 2th ed., Cuvillier Verlag Göttingen (1993)
[4] A. Wetzel, Diploma thesis, Göttingen (2007)
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