Identification of dispersoids in Al-Mg alloys containing Mn

The submicron dispersoids in the ingot of AA 5083 have been identified. They precipitate during the soaking treatment before hot working. Strong evidence suggests that most of them have the composition of MnAl₄. A smaller number belong to E phase (Mg₃Cr₂Al₁₈) and CrAl₇. The presence of the dispersoids of MnAl₄ is in contradiction with the ternary phase diagram of Al-Mg-Mn. The particle possess the shape of a rod with a hexagonal cross section. The aspect ratio ranges from one to several tens. These dispersoids may be important to the hot ductility of AA 5000 series alloys.