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.
Highlights
With the fast development of aerospace industries, the requirements of the hightemperature performance of supersonic aircraft are increasing [1,2]
It can be seen that when the creep temperature or creep stress is low, the creep curves show the occurrence of a short primary stage of creep, which lasts for about 10 h, followed by the steady creep stage (Figure 1a,c)
It is mainly determined by the difference of density number of Ω phase; The density number of the Ω phase depends on the content of Cu in Al matrix in solid solution alloys, rather than the total Cu content in alloys
Summary
With the fast development of aerospace industries, the requirements of the hightemperature performance of supersonic aircraft are increasing [1,2]. The Al–Cu–Mg–Ag alloy precipitates a fine and uniformly distributed plate-like Ω phase on the {111} planes of the matrix during the aging process, which can significantly enhance the mechanical properties and thermal stability of the alloy [5,6,7,8,9,10]. The Al–Cu–Mg–Ag alloy can meet the elevated-temperature mechanical properties and economic requirements of supersonic aircraft and has broad application prospects. Reddy et al [15] found that the creep-resistant property of Al–Cu–Mg alloy was significantly improved by Ag addition
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