Pure gold, like all pure metals, is relatively soft with a low yield point and this has several drawbacks in the fabrication of 24 ct gold jewelry, limiting design possibilities as well as making such jewelry prone to scratching and wear. The development of '990' gold-titanium alloy overcomes many of these deficiencies but has not met with much commercial success. In recent years, however, there have been a number of hardened 24 ct materials developed with finenesses of 99.,5% - 99.9%, some already in commercial production, where improved hardness and strength have been achieved by microalloying. There has been very little published on such microalloyed golds, particularly their metallurgy. This paper examines their metallurgy - the theoretical basis for hardening and some candidate alloying elements which could form the basis of microalloyed 24 ct golds. These are compared to known published information on the compositions and properties of actual microalloyed 24 ct golds. The scope for adapting the microalloying approach to 22 ct and other carat golds is also discussed.

Author: Dr. Christopher W. Corti