Distribution of Twin Boundaries on Three-Dimensional Grains of 316L Stainless Steel

The revelation of the distribution of twin boundaries on three-dimensional (3D) grains is of critical importance for the comprehension of their influence on material properties. However, this remains a significant challenge in the field of 3D material characterization. In this study, the distribution of twin boundaries on the surfaces of 3D grains in solution-annealed 316L stainless steel was systematically and quantitatively characterized using 3D electron backscatter diffraction. The results show that the average size of twin boundaries is significantly larger than that of random boundaries (approximately 52% larger). Although the size distributions of grains, random boundaries, and twin boundaries, as well as the distributions of the total number of grain boundaries and the number of twin boundaries per grain, all conform to a lognormal distribution, the area fraction of twin boundaries on grain surfaces exhibits a typical Lorentz distribution, while their number fraction shows no clear pattern. On average, each grain possesses 9.6 boundaries, of which 1.7 are twin boundaries, and the average area coverage of twin boundaries on grain surfaces reaches 38.4%. The findings offer a 3D statistical foundation for optimizing grain boundary engineering strategies in austenitic alloys.