Nano-Twinning and Martensitic Transformation Behaviors in 316L Austenitic Stainless Steel During Large Tensile Deformation

The evolutions of nano-twins and martensitic transformation in 316L austenitic stainless steel during large tensile deformation were studied by electron backscatter diffraction (EBSD) technology and transmission electron microscopy (TEM) in detail. The results show that due to the low stacking fault energy of the steel, phase transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP) coexist during the tensile deformation. The deformation firstly induces the formation of deformation twins, and dislocation pile-up is caused by the reduction of the dislocation mean free path (MFP) or grain refinement due to the twin boundaries, which further induces the martensitic transformation. With the increase of tensile deformation, a large number of nano-twins and α’-martensite appear, and the width of nano-twins decreases gradually, meanwhile the frequency of the intersecting deformation twins increases. The martensitic transformation can be divided into two types: γ-austenite → α’-martensite and γ-austenite → ε-martensite. α’-martensite is mainly distributed near the twin boundaries, especially at the intersection of twins, while ε-martensite and stacking faults exist in the form of transition products between the twins and the matrix.