Dendritic Segregation Rim
A chemical inhomogeneity along solidification arms within the microstructure, caused by differing solubilities in the liquid and solid states. It necessitates homogenization annealing.
This is the point where, during solidification of the melt, the alloying elements distribute unevenly. The structure then becomes not homogeneous, but shows a kind of 'tree structure' with different concentrations. This makes the material prone to cracking, especially when it is later loaded. If you have such a segregation band, only a proper homogenization annealing helps. The part is annealed so long and so hot until the elements are evenly distributed again. The exact temperature and time depend on the material, you have to look that up. In any case, you should not skip it, otherwise you will have trouble with cracks later.