Phase Composition and Residual Stresses in the Surface Layers of VNS9-Sh TRIP Steel

The phase composition of thin-sheet (0.3 mm thick) austenitic–martensitic VNS9-Sh TRIP steel is studied by X-ray diffraction, and the residual stresses in the steel are determined. This cold-rolled steel is a gradient material with a high content of strain-induced martensite in the near-surface laye...

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Bibliographic Details
Published in:Russian metallurgy Metally 2020-10, Vol.2020 (10), p.1129-1136
Main Authors: Betsofen, S. Ya, Ashmarin, A. A., Terent’ev, V. F., Grushin, I. A., Lebedev, M. A.
Format: Article
Language:English
Subjects:
Advanced Materials and Technologies
Austenite
Austenitic stainless steels
Chemistry and Materials Science
Cold rolling
Cold-rolled steel
Compressive properties
Crystal lattices
Elastic anisotropy
Lattice parameters
Martensite
Martensitic stainless steels
Martensitic transformations
Materials Science
Metallic Materials
Phase composition
Residual stress
Solid solutions
Stress relaxation
Surface layers
TRIP steels
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Summary:The phase composition of thin-sheet (0.3 mm thick) austenitic–martensitic VNS9-Sh TRIP steel is studied by X-ray diffraction, and the residual stresses in the steel are determined. This cold-rolled steel is a gradient material with a high content of strain-induced martensite in the near-surface layers. The austenite content in the surface layer is shown to increase from 47% (as-delivered state) to 85% after removing a 10‑μm-thick surface layer. The positive volume effect of the martensitic transformation during cold rolling leads to the relaxation of high tensile stresses up to 850 MPa in the martensite phase and to the formation of compressive stresses up to 950 MPa in austenite in the surface layer. The removal of a 10-μm-thick surface layer brings about a substantial change in the stressed state; in this case, residual tensile stresses prevail in both the phases: 400–800 MPa in martensite and 70–280 MPa in austenite. A technique is proposed for estimating the residual stresses via measuring the lattice parameters for various reflections; it makes it possible to separate the contributions of residual stresses and the solid solution composition with allowance for the elastic anisotropy of the crystal lattice.
ISSN:0036-0295
1555-6255
1531-8648
DOI:10.1134/S0036029520100067