Abstract
The processes governing the deformation and damage of C70 pearlitic steel were investigated in nanometer and micrometer scales using electron backscatter diffraction technique and “in-situ” scanning electron microscope tensile testing. The ferrite behavior was identified by “in-situ” x-ray tensile tests. Investigations were carried out on annealed microstructure with two interlamellar spacings of Sp = 170 and Sp = 230 nm. It is shown that pearlite yielding is controlled by the deformation mechanisms occurring in ferrite. Deformation and damage mechanisms were proposed. At low strain, pearlite deforms homogeneously with low misorientation (<5°) inside the pearlite colonies and elongates the cementite plates. At high strain, pearlite deforms heterogeneously in intense localized shear bands inside the more favorably oriented pearlite colonies. Misorientation reaches values up to 15°. Cementite deforms by an offset of lamella along the shear bands. The nucleation of these shear bands occurs at strain level of E 11 = 7% for coarse pearlite and at a higher value for fine pearlite. Damage occurs by brittle fracture of the elongated cementite lamellae parallel to the tensile axis and which are developed by shear micro-cracks along the slip bands. The plastic-induced damage is thus delayed by the fine pearlite structure.
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Abbreviations
- CLM:
-
Circular line method
- E 11 :
-
Macroscopic strain
- EBSD:
-
Electron backscatter diffraction technique
- HT:
-
Heat treatment
- IPF:
-
Inverse pole figure
- GAM:
-
Grain average misorientation
- KAM:
-
Kernel average images
- PQM:
-
Pattern quality map
- Sp:
-
Interlamellar spacing (nm)
- SEM:
-
Scanning electron microscope
- σy :
-
Yield stress
- Σ11 :
-
Macroscopic stress
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Acknowledgments
G. Gonzalez would like to thank the financial support from CONACYT through Project No. 166896 necessary for EBSD detector acquisition. Part of this research was made during a sabbatical year of GG at PIMM. This visit was made possible by support from PASPA-UNAM, CONACYT and ENSAM-CNAM.
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Sidhom, H., Yahyaoui, H., Braham, C. et al. Analysis of the Deformation and Damage Mechanisms of Pearlitic Steel by EBSD and “in-situ” SEM Tensile Tests. J. of Materi Eng and Perform 24, 2586–2596 (2015). https://doi.org/10.1007/s11665-015-1537-7
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DOI: https://doi.org/10.1007/s11665-015-1537-7