The precipitation behavior of Al-Cu-Mg-Ag single crystal during aging under elevated compression stresses

The Al-Cu-Mg-Ag single crystal is prepared to study its precipitation behavior during aging under elevated compression stresses. Transmission electron microscopy (TEM), high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and hardness test are used for this investigation. The results show that a compression stress of 50 MPa leads to more uniform length distribution but slightly lower number density of Omega-phase in the stress-aging sample, as compared to that of the stress-free aging sample. When a higher compressive stress of 200 MPa is applied, the number density of Omega-phase is significantly decreased while a large number density of theta'-phase are precipitated along the dislocation lines introduced by the applied stress. Furthermore, the stress-orientating effect on Omega precipitation can not be observed in Al-Cu-Mg-Ag single crystal during stress aging even under the compressive stress of 200 MPa loading along the [(2) over bar 15](Al) direction. This result signifies that the applied stress magnitude is not the only critical factor in determining whether the stress-orienting effect of Omega-phase can be generated, as this effect may be also associated with the loading orientation during stress aging. (C) 2016 Elsevier B.V. All rights reserved.