Creep Behavior and Microstructural Evolution of Al–Cu–Mg–Ag Alloys with Various High Cu Contents

Abstract

The creep behavior and microstructural evolution of three Al–Cu–Mg–Ag alloys with Cu content around its solid solubility limit in Al (5.65 wt %) were investigated at 180–240 °C and applied stress of 150–300 MPa. The creep resistance of aged alloy, which is mainly determined by the number density of Ω phase, is the best for 6.00 wt % Cu, better for 5.30 wt % Cu, and the worst for 5.65 wt % Cu. After solid-solution treatment, the lowest Cu content in the Al matrix for the alloy with 5.65 wt % Cu is observed due to the existence of more residual phases. It results in the lowest number density of Ω phase the following aging and poor creep resistance. Increasing temperature from 180 to 240 °C at the same stress (225 MPa), the steady creep rate of alloys increases by 225 times, which is apparently larger than that (26 times) for increasing stress from 225 to 300 MPa at the same temperature (180 °C). It indicates that the coarsening of the Ω phase with increasing temperature should be more serious than that with increasing stress. The creep mechanism of Al–Cu–Mg–Ag alloy can be attributed to the dislocation climb with the existence of threshold stress.

Dependence of Creep Properties on Aging Treatment in Al–Cu–Mg Alloy

“…It is noted that the stress exponents and creep activation energy of the Al–Cu–Mg alloy are much larger than those of pure Al (4.4 and 142 kJ mol −1 , respectively [ 4,5b,16 ] ), which are mainly caused by the interaction between the precipitated particles and the displacements inside the material. It suggested the existence of a threshold stress σ th .…”

Study on Creep Properties of Al-Zn-Mg-Cu Alloys

“…The results indicate that the creep rate of the alloy under low stress conforms to the Nabarro Herring theory. Peng et al [8] conducted creep tests on Al-Cu-Mg-Ag alloys with different Cu contents to investigate the effects of creep test temperature and applied stress on the creep behavior of the alloy. The experiment shows that keeping the stress constant and increasing the test temperature significantly increases the steady-state creep rate of the alloy compared to increasing the applied stress while keeping the temperature constant.…”