Issue 43

M. Tocci et alii, Frattura ed Integrità Strutturale, 43 (2018) 218-230; DOI: 10.3221/IGF-ESIS.43.17 227 After 2 min of cavitation test, besides the aforementioned different degree of plastic deformation of the Al matrix due to the heat treatment, intermetallic particles are clearly visible on the surface of both samples and appear unaffected by the erosion mechanism (Fig. 13). Figure 13: Eroded surfaces after 2 minutes of cavitation test for a) AlSi9CuFe, b) AlSi9CuFe T6 alloys. In order to better appreciate their influence, the same area was observed for AlSi9CuFe samples after 2 and 5 minutes of cavitation exposure (Fig. 14). In particular, it was chosen an area where a crater was already present, likely due to a pre- existent porosity. It can be seen that intermetallic particles located on the edge of the crater (white circles) are not removed by prolonged cavitation exposure, while material removal took place on the other sides of the crater itself, as indicated by arrows. As found also for other Al-Si alloys in a previous study [20], intermetallic particles, especially with a complex morphology, can provide additional cavitation resistance, preventing material removal. Figure 14: SEM images of the same area on the eroded surface of AlSi9CuFe samples after a) 2 min and b) 5 min of cavitation testing. As discussed for the other alloys, after 30 min of testing, a uniform material removal took place and it is not possible to identify a different deformation for diverse phases anymore (Fig. 15). Figure 15: Eroded surfaces after 30 minutes of cavitation test for a) AlSi9CuFe, b) AlSi9CuFe T6 alloys.