Enhanced structural refinement and strengthening by intermediate annealing process in a nanostructured Al-4%Cu alloy

Abstract

Cold rolling is widely used to refine the microstructure and enhance the strength of metals and alloys; however, its efficiency gradually decreases with increasing strain. This study presents a strategy to improve structural refinement and yield strength in a nanostructured Al-4%Cu alloy by incorporating element segregation and nano-sized particles to stabilize lamellar grain boundaries through an intermediate annealing process during the conventional high-strain cold rolling. An average lamellar boundary spacing of 51 nm and a yield strength of 497 MPa have been achieved at a von Mises strain of 4.9. Compared to the sample cold-rolled to the same strain without intermediate annealing, the lamellar boundary spacing was reduced by 38%, and the yield strength increased by 20%. Analysis of strengthening mechanisms indicates that the additional strengthening contribution comes from the finer lamellar spacing and increased dislocation density. This work suggests an efficient and convenient design pathway toward high-strength nanostructured Al alloys.