Alloys of Calcium

The alloys of calcium have not thus far proved to be of any great commercial importance, but, in common with the pure metal, they may prove to be useful as deoxidisers.

Cooper has patented an alloy of calcium and aluminium, containing not more than 8 per cent, calcium, for use in casting. The alloy is ductile and specifically lighter than aluminium, and, on account of its lightness, might also be used as a filling for hollow steel structures.

An alloy of calcium and lead, which has received the name of " Ulco " metal, has been put forward as a substitute for antimonial lead in the manufacture of shrapnel bullets. It contains considerably less than 1 per cent, calcium, or, better still, a mixture of calcium and barium. It is much harder than other commercial lead alloys, and it expands on solidification, forming castings free from blow-holes. The Brinell hardness of antimonial lead is about 17, and that of " Ulco " metal 22-26, according to the temperature of pouring. It can be re-melted several times without appreciable loss of hardness, and has the general appearance of ordinary lead. Tests made by the United States Bureau of Standards show that it compares very favourably with Babbitt metal for use in machinery bearings.

A bearing metal containing calcium, with a Brinell hardness of 35-45 and melting-point 370° C., has also been described. It has a yieldpoint 2½ times as high as that of the corresponding tin alloy. It consists apparently of hard crystals of a calcium-lead compound embedded in a softer mass of mixed crystals of lead and other metals.

A large number of other alloys of calcium have been studied, but they are of theoretical interest only. The general methods of preparation are:

1. simple fusion together of the two metals;
2. reduction of a calcium salt in the presence of another metal, or simultaneous reduction of a mixture of compounds of the two metals;
3. electrolysis of the fused calcium chloride, using a cathode of the second metal in the molten state.

The energy with which calcium reacts with the metals increases with increasing atomic weight of the latter.

In general, the alloys decompose water with more or less vigour according to the amount of calcium they contain.