Mesoscopic Strain Fields Measurement During the Allotropic α − γ Transformation in High Purity Iron
- 71 Downloads
The allotropic phase change from ferrite to austenite represents a moment of massive interplay between the microstructural and mechanical states of iron. The difference of compacity between the two phases induces a microplastic accommodation in the material at grain scale. However, mechanical heterogeneities resulting from the transformation process remain challenging to characterise due to the high temperature conditions it is associated with. We developed experimental equipment for in situ observation of α − γ and γ − α transformations. Images of the surface of an iron sample taken by an optical camera were used as input for a Digital Image Correlation (DIC) routine. Special care was taken to maximize image resolution to capture sub-grain phenomena. Observations show that, at the mesoscopic scale, shear strain fields exhibit strong localisations that are evidence of transformations that are occurring.
KeywordsDigital image correlation High temperature Allotropic transformation Pure iron
This work is part of the SMICE project, which was funded by BPI France under grant P113013-2660682. The authors are extremely grateful to Julien Réthoré for providing access to the UFreckles software and for giving precious advice on how to use it.
- 1.Liu Y, Sommer F, Mittemeijer E (2004) Abnormal austenite-ferrite transformation behaviour of pure iron. Philos Mag 84:18:1853–1876Google Scholar
- 2.Basinski Z, Hume-Rothery W, Sutton A (1955) The lattice expansion of iron. In: Proceedings of the Royal Society AGoogle Scholar
- 11.Strangwood M (2012) Phase Transformations in Steels, Woodhead Publishing Limited, chap Fundamentals of ferrite formation in steelsGoogle Scholar
- 15.Zhang Z, Machin G (2009) Experimental Methods in the Physical Sciences, Elsevier, chap Overview of Radiation thermometryGoogle Scholar
- 16.Lyons J, Liu J, Sutton M (1996) High-temperature deformation measurements using digital image correlation. Meas Sci Technol 36:64–70Google Scholar
- 21.Réthoré J (2018) Ufreckles. https://doi.org/10.5281/zenodo.1433776
- 26.Wilkinson A (2000) Electron Backscatterd Diffraction in Materials Science, Springer, chap Measuring strains using electron backscattered diffractionGoogle Scholar