Cryogenic reciprocating torsion induced nanoscale precipitation in aluminum wire with exceptional strength and electrical conductivity

Cryogenic reciprocating torsion (CRT) was used to trade off strength and electrical conductivity in aluminum wires. Compared with the initial sample, the CRT processed aluminum wires possess higher strength without significant sacrifice of electrical conductivity. The ultimate tensile strength increases by 76% with a slight decrement of 1% IACS in electrical conductivity. Microstructural characterizations show that CRT induces multiple gradient structures (MGSs) on the cross-section of aluminum wires: dislocation density gradient, grain size gradient, and precipitate size gradient. In particular, a bimodal distribution of precipitate size was observed in CRT processed aluminum wires. A theoretical model considering the above microstructures was proposed to explain the excellent properties. The experimental results validate the reasonability of the present model. The further theoretical analyses reveal that nanoscale precipitates contribute more to the exceptional strength and electrical conductivity than other microstructures.