After a brief presentation of the production plant, the high pressure die casting process is described in a more detailed way. Deeply investigating into the details of the process the movement of the die are explained, especially the strokes of the radial carriers, to let the reader understand what are the function of the broken piece, analyzed in this thesis, inside the cycle. The first approach to the fracture analysis consists into a visual inspection, immediately comes out that there is a localized deterioration of the surface of the fillet, concentrated on the right side. From this damaged area a specimen was obtained and inspected in a more accurate way at SEM (Scanning Electron Microscopy) to investigate the morphology of the fillet damaged surface and of the fracture surface.