Effect of Mg on the fracture characteristics of cast Al–7Si–Mg alloys

The fracture behavior of Al–7Si–Mg cast alloys mainly depends on the size and shape of eutectic silicon particles and iron-rich intermetallics. These can be altered by many ways such as, chemical modification, cooling rate, magnesium content and iron-rich intermetallics. Magnesium increases the matrix strength, but decreases the ductility. Further, cast Al–7Si–Mg alloys can be strengthened by heat treatment processes to attain desirable mechanical properties. Crack tortuosity, crack branching factor (CBF) and tendency of crack propagation through eutectic regions are quantified in order to study the formation and growth of fatigue crack. The crack propagation in the Al–Si–Mg alloys depends on the morphology of silicon particles, cell size and Mg content. The fracture toughness values measured are found to decrease with increase in magnesium content at the optimized T-6 heat treated condition.