Tripling hardness of gold by micro alloying coupled with cold processing

Gold has broad applications in jewelry, but suffers from low hardness. In the present work, we show that simultaneous addition of 0.1 wt.% Ce and Si can nearly double the hardness of fine gold. We further show that hardness can be tripled by subsequent cold processing. By systematic structural characterizations and thermal analysis, we find that Ce and Si tend to segregate to grain boundaries and impede grain growth. Our work is helpful for development of new gold micro alloys and for design of jewelry that is more wear and scratch resistant.