The consolidation of metals: the origin of bifilms

During their processing from ores, all metals go through a particulate stage. These separate pieces have to be consolidated usually with heat and pressure to form useful engineering forms. In the case of metals which undergo a melting stage, the pouring and stirring actions which are commonly employed disintegrate the liquid into splashes and droplets which appear to mutually assimilate, creating a consolidated bulk liquid. However, in every case, whether consolidation takes place in the solid or liquid states, the consolidation mechanism naturally incorporates an oxide-to-oxide interface (although occasionally other surface films such as nitrides and pure carbon are involved). The concept of the meeting of oxides is of course assumed to be trivial and therefore almost universally overlooked. However, the consequences seem to be far from trivial. The creation of opposed, double (never single), unbonded oxide films, called ‘bifilms’ by the author, acts as cracks. They can survive extensive plastic working and seem to be prolific throughout metallurgy. They appear to exert significant control over the failure properties of metals, by both cracking and corrosion. They are proposed to constitute the Griffith cracks required for the failure of metals by fracture and fatigue. Bifilms may now be eliminated from some of our liquid processing routes, enabling for the first time the production of crack-resistant and corrosion-resistant metals.