Interdendritic Liquid Pocket
Trapped pockets of final liquid phase within the interstices of highly developed dendritic arms near the end of solidification.
Residual melt inclusions are basically liquid metal residues that get trapped between dendrite arms during solidification and harden there as pores or shrinkage cavities. This happens when the melt cannot flow cleanly and cooling is unfavorable. These things are bad for the structure because they reduce density and can act as crack starting points, especially when the weld is later loaded. To avoid them altogether, you need to ensure uniform, controlled cooling and let the melt flow properly—so don't work too hastily and keep heat input under control. If you run the weld clean and steady, you usually won't have issues with inclusions.