WEB Characterization of micro deformation behavior in duplex stainless steels
Characterization of micro deformation behavior in duplex stainless steels
Guocai Chai1,2* and R. Lin Peng1
1Engineering Materials, Linköping University, 58183 Linköping, Sweden
2AB Sandvik Materials Technology, 81181 Sandviken, Sweden
Duplex stainless steels consist of a FCC austenite and a BCC ferrite two phases. Since they have different crystallographic structures, elastoplastic properties and deformation hardening, the material has micro heterogeneous deformation behaviors in nature. This can significantly affect the material properties such as stress corrosion cracking resistance and fatigue strength. A fundamental understanding of the influence of macro loading and microstructure on the micro yielding and damage behavior of the individual phases is therefore important to material development and applications.
This work shows a study on the micro deformation behaviors in the austenitic and ferritic phases of some duplex stainless steels using X-ray and synchrotron diffraction with in-situ uniaxial tensile load, and neutron diffraction with in-situ compression load. Cyclic deformation behavior was studied using in-situ loading under EBSD. The results show that at low plastic strains, a load transfer from austenitic phase to ferritic phase occurs due to higher yield strength and strain hardening rate of the ferrite. However the austenite hardens more rapidly than the ferrite at larger plastic strains. There are stronger intergranular interactions among the hkl planes of austenite than those of ferrite. Cyclic plastic strains are also inhomogeneous. Damage and crack initiation depend on not only the initial strength of the individual phases, but also their deformation hardening behavior. The weaker phase after cyclic loading becomes damaged and hence exhibits crack initiation first. TEM investigation shows that the dislocation slipping behavior and formation of substructures strongly depend on the elasto-plastic properties of the individual phases and the coupling effect. This study provides a better understanding of micro-deformation behavior in austenitic and ferritic phases with different stress conditions and different chemical composition.
Duplex stainless steels, heterogeneous deformation behavior, diffraction