AN OBSERVATION OF UNHEALED POROSITIES AND CRYSTALLINE STEPS IN ALUMINIUM ALLOY FORGINGS

Unhealed porosities and free surface of dendrites with crystalline steps were occasionally observed in aluminium alloy forgings. It was found that the dendrites grow preferentially along <100> directions and the crystalline steps belong mainly to {100} and {110} planes.In the neighbourhood of the unhealed porosities the alloy matrix appeared to be embrittled and in certain cases cleavage fracture was observed.