Tracking inclusions in aluminium alloy castings using positron emission particle tracking (PEPT)

Inclusions in castings lead to the initiation of fatigue cracks and are detrimental to their mechanical properties. Computer simulations of the casting process include models of inclusion movement but there is currently no method of experimentally verifying these models. The technique described here used positron emission particle tracking (PEPT) to follow the movement of radioactive alumina particles entrained in a liquid aluminium alloy as the mould was filled, thus showing the behaviour of inclusions in castings. Five experiments were carried out with two different alumina particle sizes, inserted into a simple cast plate made in resin bonded sand moulds. Besides demonstrating the value of the experimental technique, these experiments showed how inclusion movement in castings was greatly affected by the random nature of the fluid flow during mould filling.