Cavitation in liquid and solid metals: Role of bifilms

At normal engineering stresses and temperatures cavitation in metals appears to be theoretically impossible. It is proposed that the only common viable initiating mechanism for cavitation in both liquid and solid metals is an atomically unbonded mesoscale interface. Such features are provided by entrainment defects from an original consolidation process such as casting or powder metallurgy. In most metals entrainment defects occur as a result of turbulence during the original melting and pouring of the liquid metal. The most common entrainment defects are bubbles and bifilms. Both are present in large populations in most metals and present easy initiation sites for cavitation and for the precipitation of second phases which are thereby made to appear brittle as a result of the enshrined bifilm crack. The promise of metals free from entrainment defects is briefly reviewed.