Micromechanics and microstructure evolution during in situ uniaxial tensile loading of TRIP-assisted duplex stainless steels

摘要

Transformation-induced plasticity (TRIP) assisted duplex stainless steels, with three different stabilities of the austenite phase, were investigated by synchrotron x-ray diffraction characterization duringin situuniaxial tensile loading. The micromechanics and the deformation-induced martensitic transformation (DIMT) in the bulk of the steels were investigatedin situ. Furthermore, scanning electron microscopy supplemented thein situanalysis by providing information about the microstructure of annealed and deformed specimens. The dependence of deformation structure on austenite stability is similar to that of single-phase austenitic steels with shear bands andbcc-martensite (α′) generally observed, and blockyα′is only frequent when the austenite stability is low. These microstructural features, i.e. defect structure and deformation-induced martensite, are correlated with the micro- and macro-mechanics of the steels with elastoplastic load transfer from the weaker phases to the strongerα′, in particular this occurs close to the point of maximum rate ofα′formation. A clear strain-hardening effect fromα′is seen in the most unstable austenite leading to a pronounced TRIP effect.