In Situ TEM Observation on Martensitic Transformation during Tensile Deformation of SUS304 Metastable Austenitic Stainless Steel

Abstract

Through in situ transmission electron microscopy observation on SUS304 metastable austenitic stainless steel during stretching at room temperature, it is found that ε martensite plates were induced preferentially from the sites of dislocation pile-ups. With increasing deformation, some of ε thin martensite platelets disappear and reversibly transform to γ austenite without heating treatment, which is different from the previous result that ε martensite can entirely transform to α′ martensite. Then, some of deformation twins appear and grow along the vertical direction of ε martensite due to$(111)_{\gamma }\, \bot (10\bar{1}0)_{\varepsilon }$. Moreover, it is directly observed that multiple transformation mechanisms via γ → ε → γ, γ → ε, γ → α′, γ → ε → α′, γ → deformation twins → α′ can co-exist.