Berlin 2005 – wissenschaftliches Programm

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M: Metallphysik

M 16: Phasenumwandlung I

M 16.4: Vortrag

Samstag, 5. März 2005, 10:00–10:15, TU H1058

Influence of Twin Grain Boundaries on Texture Evolution during α-γ-Phase Transformation in Microalloyed Steels — •Ingo Lischewski und Günter Gottstein — Institut für Metallkunde und Metallphysik, RWTH Aachen, D-52056 Aachen, Germany

The partial ferrite to austenite phase transformation in microalloyed steel was studied, with a special focus on the influence of twinning on the texture evolution. During the diffusion controlled phase transformation a texture memory effect takes place. This effect is explained by different orientation relationship models. The present models are not capable of quantitatively predicting the texture changes during phase transformation. Various mechanisms known that cause a texture change. This study demonstrates the influence of twin formation on the transformation texture.

Samples of a microalloyed steel were wrapped in a CrNi-18/9 steel foil and annealed at a low transformation temperature. Nickel is believed to diffuse from the steel wrapping into the sample, and to stabilize the austenite and retain it on cooling to ambient temperature. This allows us to measure locally by EBSD the orientation of the ferrite prior to transformation and at the same location the orientation of the austenite subsequent to transformation. The measurements were conducted in a high resolution FEG-SEM.

The study demonstrates an influence of twin grain boundaries on the development of transformation textures. Mainly Σ3 und Σ9 twin grain boundaries in the austenite phase are observed. The twin grain boundaries are not randomly distributed over the whole microstructure.