IMPACT PROPERTIES OF AL-SI-CU ALLOYS

The charpy impact energy of Al-Si-Cu alloys has been measured. Instrum ented charpy impact tests have been conducted at 25-degrees-C, 100-deg rees-C and 150-degrees-C. The charpy specimens were machined from plat e castings or tapered cylindrical castings. The plates were produced i n CO2 sand molds and tapered cylinders were produced in water cooled C u molds. Both unmodified and Sr modified castings were tested. The eff ects of solution treatment on microstructural parameters were studied by optical microscopy. The results indicate Sr modification refines Si , Fe and Cu rich phases in the interdendritic regions. The charpy impa ct energy increases upon Sr modification. The impact energy in the T6 condition does not vary significantly from the as-cast value for typic al solution times used in commercial practice.