The aim of the research on the newly developed eutectic silumin type AlSi9NiCuMg0.5, developed and patented by a team of staff of the Faculty of Mechanical Engineering, was to determine the cause of the cracking of castings under operating conditions. When the technology was put into practice, the casting was cast and then used to break the entire casting section and create a crack that crosses the whole cross section. Castings were cast by low-pressure die casting technology, where the mold is fed into the mold cavity via a cast iron tube. The essence of the research was to perform a fractographic analysis of the fracture area, to identify the structure of the casting, to identify the structural components on the surface of the fracture surface by EDS analysis on an electron scanning microscope and to determine the chemical composition of the material in the area of refraction compared to the declared alloy. From these results we can clearly identify the cause of premature cracking of castings from the newly developed eutectic silumin. Additionally, material analyzes have been carried out to see if the material has been contaminated with iron, for example by dissolving a cast-iron filler tube or a batch material. From all the analyzes and fractographic investigations carried out, it can be stated that the initiator of crack insertion and the subsequent cracking of the casting under load is the high content of rough fragments of the fractured intermetallic phases of the Al5FeSi type on the fracture surface (over 20%), which are subject to fission. The high iron content was due to the dissolution of the cast iron ascension tube by low-pressure casting.
