700 



BELL SYSTEM TECHNICAL JOURNAL 



0.02 



0.04 0.06 0.08 0.10 0.12 0.14 

 WEIGHT PER CENT CALCIUM 



0.16 0.18 



Fig. 1 — A partial equilibrium diagram of the system lead-calcium, according to 

 Schumacher and Bouton. 



varies continuously from 0.10 per cent at 328° C. to about 0.01 per cent 

 at room temperature. Moreover, when the 0.10 per cent alloy is 

 cooled below 328° C, the calcium precipitates out of the solid solution 

 in the form of PbsCa. This precipitation, while a gradual process, 

 can be hastened by suitable heat treatment. Physically, the effect of 

 the PbsCa molecules highly dispersed throughout the body of the alloy 

 is to strengthen and harden it very materially. Thus, the alloy with a 

 calcium content of 0.10 per cent has a tensile strength of around 

 8,000 pounds per square inch, a value comparable to that reached by 



