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Effect of pre-straining and bake hardening on the microstructure and mechanical properties of CMnSi TRIP steels

Conference Paper


Abstract


  • The effects of pre-straining and bake hardening on the mechanical behaviour and microstructural changes were studied in two CMnSi TRansformation-Induced Plasticity (TRIP) steels with different microstructures after intercritical annealing. The TRIP steels before and after pre-straining and bake hardening were characterised by X-ray diffraction, optical microscopy, transmission electron microscopy, three dimensional atom probe and tensile tests. Both steels exhibited discontinuous yielding behaviour and a significant strength increase with some reduction in ductility after pre-straining and bake hardening treatment. The following main microstructural changes are responsible for the observed mechanical behaviours: a decrease in the volume fraction of retained austenite, a increase in the dislocation density and the formation of cell substructure in the polygonal ferrite, higher localized dislocation density in the polygonal ferrite regions adjacent to martensite or retained austenite, and the precipitation of fine iron carbides in bainite and martensite. The mechanism for the observed yield point phenomenon in both steels after treatment was analysed.

UOW Authors


  •   Zhang, L C. (external author)
  •   Timokhina, Ilana B. (external author)
  •   La Fontaine, A (external author)
  •   Ringer, Simon Peter. (external author)
  •   Hodgson, Peter D. (external author)
  •   Pereloma, Elena

Publication Date


  • 2008

Citation


  • Zhang, L. C., Timokhina, I. B., La Fontaine, A., Ringer, S. P., Hodgson, P. D. & Pereloma, E. (2008). Effect of pre-straining and bake hardening on the microstructure and mechanical properties of CMnSi TRIP steels. Proceedings of the 3rd International Conference on Thermomechanical Processing of Steels (p. Paper 83).

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  • Paper 83

Abstract


  • The effects of pre-straining and bake hardening on the mechanical behaviour and microstructural changes were studied in two CMnSi TRansformation-Induced Plasticity (TRIP) steels with different microstructures after intercritical annealing. The TRIP steels before and after pre-straining and bake hardening were characterised by X-ray diffraction, optical microscopy, transmission electron microscopy, three dimensional atom probe and tensile tests. Both steels exhibited discontinuous yielding behaviour and a significant strength increase with some reduction in ductility after pre-straining and bake hardening treatment. The following main microstructural changes are responsible for the observed mechanical behaviours: a decrease in the volume fraction of retained austenite, a increase in the dislocation density and the formation of cell substructure in the polygonal ferrite, higher localized dislocation density in the polygonal ferrite regions adjacent to martensite or retained austenite, and the precipitation of fine iron carbides in bainite and martensite. The mechanism for the observed yield point phenomenon in both steels after treatment was analysed.

UOW Authors


  •   Zhang, L C. (external author)
  •   Timokhina, Ilana B. (external author)
  •   La Fontaine, A (external author)
  •   Ringer, Simon Peter. (external author)
  •   Hodgson, Peter D. (external author)
  •   Pereloma, Elena

Publication Date


  • 2008

Citation


  • Zhang, L. C., Timokhina, I. B., La Fontaine, A., Ringer, S. P., Hodgson, P. D. & Pereloma, E. (2008). Effect of pre-straining and bake hardening on the microstructure and mechanical properties of CMnSi TRIP steels. Proceedings of the 3rd International Conference on Thermomechanical Processing of Steels (p. Paper 83).

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  • Paper 83