THE SAFETY OF MOLTEN ALUMINIUM-LITHIUM ALLOYS IN THE PRESENCE OF COOLANTS

Abstract
The conventional, large scale techniques employed for casting fabrication ingot in aluminium alloys allow, in certain circumstances, the molten alloy to come into contact with water. Industry codes of practice have been developed that reduce the likelihood of explosions in these "run-out" situations to a very low level. It has, however, been demonstrated that the hazard is much greater when aluminium alloys containing lithium come into contact with water. This paper describes experiments to assess the extent of this hazard. It is demonstrated that if an explosion occurs, the energy released increases with lithium content in an exponential manner. The situation with alternative coolants such as water-polyalkalene glycol mixtures or various pure alcohols has also been assessed. Explosions were shown to be possible with al1 of the coolants examined. Depending upon the degree of sub-cooling with the particular alcohol involved, the energy released in explosions could be greater than, or less than, that released with water as coolant. The reasons why lithium containing alloys behave differently from conventional aluminium alloys are considered and mechanisms to explain the greater release of energy are suggested.