Comprehensive Strengthening of Microalloyed Pure Gold

The hardness of pure gold jewellery is low which makes it difficult to meet structural design and performance requirements, and restricts its artistic value. In this research, scandium, calcium, and magnesium were used as alloying elements with pure gold, and the microstructure and hardening behaviour of modified pure gold were studied through cold-working, solid solution, and aging treatment. The results showed that the as-cast hardness of an Sc-Ca-Mg alloyed pure gold could reach HV64: after solution treatment at 700 °C, the hardness could reach HV55, and the microstructure in its solid solution state presented a homogeneous single phase. When the modified pure gold was deformed and the deformation rate reached 80%, the hardness reached HV118, after aging treatment at 250 °C and small precipitation phases were dispersed in its structure; the resultant grain size was finer than that of pure gold, and the hardness reached HV133. The hardening behaviour of this modified pure gold was the comprehensive effect of solid solution strengthening, fine-grain strengthening, deformation strengthening, and precipitation strengthening.