Pure gold, platinum and silver, like all pure metals, are relatively soft with a low yield points and this has several drawbacks in the fabrication of 24ct gold, platinum and silver jewellery, limiting design possibilities as well as making such jewellery prone to scratching and wear. This softness is also an issue wih high fineness jewellery alloys such as 22 ct golds.

For 24 ct gold, the development of ‘990’ gold – titanium alloy in the late 1980s overcame 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 gold materials developed with finenesses of 99.5% or higher, some in commercial production, where improved hardness and strength have been achieved by microalloying. Furthermore, microalloyed silver and platinum have also been developed and commercialised. This topic was reviewed at JTF 2005 but, since then, there has been further published research and commercial developments and this presentation updates the original 2005 review and extends it to include high fineness alloys.