Investigation of Evolution of Inclusions in 15-5PH Stainless Steel During Hot Compression Using 3D X-Ray Microscopy

Non-metallic inclusions in steel disrupt the continuity of the matrix and decrease the strength and toughness of steel. This study analyzed the composition of the inclusion and two-dimensional size distribution in 15-5PH stainless steel using an automatic inclusion analysis system. The results showed that the composition was determined to be mainly Al–Si–Mn–O composites, and the average area, average equivalent diameter, and face fraction percentage of were 39.35 μ m 2 , 5.86 μ m, and 0.031 pct, respectively. The three-dimensional (3D) morphology and spatial distribution of the inclusions were further demonstrated using 3D microscopy (3D-XRM). The average volume, equivalent diameter, and volume fraction were 215.83 μ m 3 , 7.44 μ m, and 0.023 pct, respectively. Compared to SEM, 3D-XRM could obtain the internal information of the sample non-destructively and display the 3D morphology of inclusions more intuitively. Subsequently, the morphology, aspect ratio and spatial orientation of the inclusions at 1453 K under different deformation ratios were compared using 3D-XRM. As compression increased, the 3D morphology changed from spherical to flat, and the average aspect ratio and spatial orientation angle of the inclusions gradually increased, which indicated that the inclusions have excellent deformation ability. The deformability of the inclusions first increased and then decreased with the increasing of compression especially the large ones.