## 4 Discussion  
### Phase Transformation Behavior During Deformation  
Figure 5 illustrates the X-ray diffraction patterns of 316L stainless steel subjected to various deformation parameters. The 316L stainless steel samples exhibited the induction of martensite through deformation, specifically \(\alpha^{\prime}\)-martensite [18], following different degrees of compressive deformation. The intensity of the austenite \(\gamma\) (111) diffraction peaks diminish as the deformation parameters increase, indicating that \(\alpha^{\prime}\)-martensite is derived from austenite [10], and the relative content of martensite increases with the extent of deformation. XRD analysis revealed that a significant number of dislocations and other defects emerged in the 316L austenitic stainless steel during compressive deformation, bringing about the transformation of some austenite into martensite. The following figure presents the EBSD analysis of the specimen under various deformation conditions. The plastic deformation of 316L austenitic stainless steel, along with the slip surfaces and grain boundaries, contributes to the generation of a significant number of dislocations, leading to a distortion of the dot matrix. During the process of plastic deformation, brittle carbides and other constituents present within the grains are fractured and subsequently distributed along the direction of flow. The distribution of dislocations is also illustrated in the Kernel Average Misorientation (KAM) diagram, which indicates that the dislocation density increases with a rise in the volume of deformation. In comparison to other samples, the dislocation distribution depicted in Figure 6e exhibits a greater degree of homogeneity and a higher relative density of dislocations. Figure 4: The Tafel polarization curves of different deformations of the plasma-nitrided samples. Figure 5: The X-ray diffraction patterns of 316L stainless steel under varying morphological conditions. The left side of Figure 7 displays the image quality map (IQ map) of the specimen. It is evident that when the deformation variable is small, the resulting martensite structure is predominantly blocky, with a minimal presence of slaty martensite. As the deformation variable increases, the intrinsic strain and twinning structure of the martensite cause it to appear darker in the IQ map. Regarding the martensite transformation during the compression deformation of 316L stainless steel, it can be analyzed by using the phase distribution diagram of the specimen on the left side of Figure 8, where the red area represents the martensite organization and the green represents the austenite organization. From the quality of the map, it can be seen that the darker lath-like region and the map-phase distribution map of the martensite-phase (red area) overlap, but as can also be seen, there are a multitude of obvious shear zones and lath-like twin crystals and martensite nucleation in the vicinity of this; these are the favorable locations for martensite nucleation. Martensite nucleation can also occur in the range of the isolated shear zones, grain boundary/shear zones intersections, etc. [19]. From the right side of Figure 8, the orientation of the distribution maps can be seen, corresponding to the increase in deformation amount; due to the serious compression deformation, the original grain boundaries gradually become fuzzy, and only the existence of deformation twins and a large number of shear bands can be seen vaguely. The martensite contents in the specimens under different deformation amounts were calculated to be 0.74%, 2.21%, 9.38%, 20.0%, and 20.5%, respectively, which increased significantly compared with the un-compressed specimens, and with the increase in deformation amount, the content of lath-like martensite increased.