In-situ analysis of phase transformation behavior of metastable austenite- martensite in stainless steel

Abstract

The in-situ EBSD analysis method was used to systematically study the effect of retained austenite characteristics on the phase transformation behavior of ferritic stainless steel after the quenching and partitioning （Q&P） process. The results show that the phase transformation behavior of retained austenite during deformation is related to its grain size， distribution， and morphology， and its influence degree is arranged in descending order. Compared with inter-martensitic austenite and inter-martensite-ferrite austenite， the trigeminal and twin austenite are more prone to martensitic transformation in the early stage of deformation. This is closely related to the different strains or stresses applied to different distributed retained austenites during deformation. Compared with large-sized austenite， small-sized austenite begins to transform in the later stage of deformation， which is helpful to prolong the uniform elongation. This may be due to the higher interfacial energy and average C content of small-sized austenite， and the need for larger macroscopic stress/strain to induce martensitic transformation due to the strengthening effect of fine grains. The elongated/equiaxed austenite is easy to transform in the early stage of deformation， while the transformation of thin film-retained austenite is mainly concentrated in the later stage of deformation， which is helpful to further improve plasticity. The different transformation behaviors are due to the differences in C and N content， as well as the presence of defects such as stacking faults， dislocations， and slip.

Keywords

• ferritic stainless steel
• in-situ analysis
• phase transformation behavior
• retained austenite
• plasticity