Internal defects of die-cast parts: Characteristics and causes of occurrence

(1) Characteristics:
During mechanical processing or metallographic examination, if fine particles or blocks with higher hardness than the metal matrix are found on the casting surface, it will cause severe wear of the cutting tools and result in different brightness on the machined surface.
(2) Causes:
① Oxides mixed from the surface of the alloy liquid;
② Reaction products between aluminum alloy and the lining of the furnace;
③ Foreign substances intruding into the metal material;
④ Inclusions.