通过变形促进析出的θ'近似相提高Al-Cu合金的力学性能

he effect of large pre-deformation on the age hardening behaviors, tensile properties and precipitate characteristics in an Al-Cu alloy during artificial ageing have been investigated using mechanical property measurements and electron microscopy. It is shown that a room-temperature rolling of Al-Cu alloy with a thickness reduction of 80% plus a subsequent artificial ageing can result in a strength increase by 35% without sacrificing ductility, with respect to that of the alloy peak-aged by a conventional heat treatment process (T6). After post-ageing at 150 oC, a large quantity of dislocations accumulated during cold-rolling is retained in Al-Cu alloy. Though dense dislocation walls and dislocation tangles existed in cold-rolled Al-Cu alloy were expected to result in micro-structural heterogeneity, the plate-shaped precipitates on {001}Al planes exhibit an exceptionally uniform distribution. Atomic-scale angular dark-field scanning transmission electron microscopy (ADF-STEM) reveals these precipitates are θ'-approximants with a crystal structure similar with the well-known tetragonal θ' phase but with the absence of Cu atom at the body-centered position. In addition, the precipitate sizes are considerably refined as compared to the θ' precipitates formed in T6 peak-aged alloys. Our results suggest the deformation-modified precipitation may play a vital role in achieving better strength-ductility synergy.