Journal of Materials Research and Technology (Sep 2022)
Deformation behavior of retained austenite and its effect on plasticity based on in-situ EBSD analysis for transformable ferritic stainless steel
Abstract
The relationship of deformation behavior of retained austenite with its characteristics for transformable ferritic stainless steel by Q&P treatment was systematically investigated using in-situ EBSD analysis. During deformation, the transformation behavior of retained austenite has to do with its texture, morphology, distribution and grain size, which are listed in ascending order of influence intensity. Small grain size, location within martensite or at martensite and ferrite phase boundaries, small grain shape aspect ratio or low transformation potential will be conducive to heightening the stability of retained austenite. Retained austenite with the features strengthening its high stability can contribute to prolonging uniform elongation at the later stage of deformation. The obvious rotation is observed prior to transformation for austenite grain that is relatively stable during deformation, and grains with similar orientation undergo similar rotation paths. In addition to martensitic transformation, crystal rotation can contribute to plasticity. Improving plasticity generated by retained austenite for Q&P treated ferritic stainless steel can be explained by combining its two different deformation modes. Furthermore, during deformation, the strain is unevenly distributed in the martensite, ferrite and retained austenite, and martensite and ferrite accommodate most plastic deformation through the strain undertaken by their corresponding grains. However, the martensitic transformation of retained austenite becomes more critical with the continuous deformation, especially at the final stage of deformation. Retained austenite with the characteristics resulting in high stability is essential for maintaining ductility at large strain during deformation of Q&P treated ferritic stainless steel.
