Effect of intermediate deformation and artificial ageing on the mechanical properties of a Al-Cu-Mg alloy

Abstract

The effect of pre-stretching and artificial ageing on the decomposition of the supersaturated solid solution (SSSS) and mechanical properties of modern high-strength duralumin AA2624 (according to the Aluminum Association classification) was investigated in the work. For this purpose, solution treated at 495°C alloy was quenched and pre-streined by 1%, 5% and 10% via uniaxial tension method and aged at 190°C with a duration ranging from 0.5h to 52h. Solution treated alloy demonstrates low strength but excellent ductility. The yield, ultimate strength and elongation to failure were 139±4 MPa, 373±1 MPa and 23±1%, respectively. Pre-deformation provides an increase of dislocation density. Enhanced amount of dislocations serve as sites for heterogeneous nucleation of strengthening particles, which leads to a significant increase of strength. Lattice defects generated by deformation change the kinetics of the decomposition of the supersaturated solid solution. It was found that the ageing of deformed by 10% is accelerated, which reflects a reduction peak ageing time by 3 times compared to single ageing (i.e. T6 treatment). Pre-stretching enhances effect of age hardening. As a result, the yield stress (480±5 MPa) of alloy under T810 treatment increases by 2 times compared to T6. Thus, pre-stertching causes a significant increase in strength, which indicates the effectiveness of T8 treatment for Al-Cu-Mg alloys.