In-situ study on the coordinated deformation mechanism of austenitic stainless steel with mixed crystal degree

Abstract

A novel in-situ tensile experiment is designed to investigate the coordinated deformation mechanism between coarse grains (CGs) and fine grains (FGs) in the mixed crystal structure of X2CrNiMo18.12 austenitic stainless steel (X18.12). In-situ electron backscatter diffraction (EBSD) and scanning electron microscopy (SEM) techniques are employed. The experiment involves quantitatively calculating the initial order and number of slip systems, rotation rate, and rotation path of FGs in two groups of mixed crystal structures with different degrees of mixing. The results reveal that the slip trace is predominantly generated in the CGs which have harder crystal orientation at a small deformation of 1.4 %. It is observed that the activation of slip traces in FGs becomes increasingly challenging as the degree of mixed crystal increases. The crystallographic orientation of the grains exhibited a certain degree of rotation to facilitate slip activation. Analysis of grain rotation demonstrates that most grains rotated along the [111] direction during the in-situ tensile test. Additionally, grains with a grain size below 100 μm typically follow a single rotation path but exhibit a high rotation rate. Comparing the mixed grain structures with mixed crystal degrees of 7 and 3, it is observed that the former exhibited a higher grain rotation rate, further indicating the increased difficulty in achieving coordinated deformation in structures with a higher degree of mixed crystal. These findings provide valuable insights into the synergistic deformation behavior of CGs and FGs in mixed crystal structures.