Effects of Calcium, Tin, and Bismuth on the Early Strength of Calcium-Lead Alloys

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Abstract
The effects of calcium content as well as additions of tin and bismuth on the mechanical properties of calcium‐lead alloys have been investigated. The alloys were wrought and heat‐treated in order to avoid the problems raised by the presence of casting variables. The previously reported increase in the rate of hardening with increasing calcium content was confirmed. Binary alloys containing less than 0.04% calcium showed no strengthening 1 hr after quench from the solution treatment temperature, while 0.1% calcium nearly doubled in tensile strength in only 5 min. Tin, in additions of 0.5 and 1%, completely restrained hardening in the first hour after quench in both 0.06 and 0.1% calcium alloy. Bismuth additions were made up to 1000 ppm. No effect was noted on the early strength of the 0.1% calcium alloys, but the rate of hardening of the 0.06% calcium alloys was significantly enhanced by the presence of bismuth. This effect, as well as the increase in hardening rate due to increased calcium are shown by means of transformation kinetics calculation to be the result of grain refinement in the alloys caused by calcium and bismuth. These findings show that early strength of calcium‐lead alloys may be improved by: (i) limiting tin content; (ii) increasing calcium content; or (iii) adding bismuth to lower calcium alloys.

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