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

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 degrees C and applied stress of 150-300 MPa. The creep resistance of aged alloy, which is mainly determined by the number density of omega 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 omega phase the following aging and poor creep resistance. Increasing temperature from 180 to 240 degrees 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 degrees C). It indicates that the coarsening of the omega 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.

Automated summary

The study found that among Al-Cu-Mg-Ag alloys with different Cu content around its solid solubility limit in Al, the alloy with 6.00 wt % Cu exhibited the best creep resistance after aging, while the alloy with 5.65 wt % Cu showed the worst creep resistance. Additionally, increasing temperature led to a more significant increase in the steady creep rate of the alloys.