Overcoming the trade-off between conductivity and strength in copper alloys through undercooling.

With the continuous development of high-performance copper alloys in modern industries, it becomes increasingly challenging to further enhance their conductivities. The key bottleneck is the existence of an upper limit on the amount of precipitation, leading to inadequate purification of the copper matrix. Here we demonstrate a phenomenon of significant conductivity enhancement in a Cu-Be alloy through undercooling. It shows that lots of spherical Be-rich clusters can spontaneously form in the deeply undercooled alloy. These clusters survive after subsequent solution treatment and are independent from the normal precipitates during aging, thereby leading to additional purification of the copper matrix. Under peak aging, the electrical conductivity of the undercooled alloy reaches up to 80% International Annealed Cu Standard, which is 30% higher than that of the same component alloy prepared in a conventional way, while its strength remains high. Our study provides an alternative way to address the long-standing strength-conductivity trade-off in copper alloys.