Mechanism controlling the thickening of T ₁ phase in an Al–Cu–Li–Mg–Ag alloy

Thermal stability and mechanical properties of Al alloys can be critically influenced by the coarsening mechanism of their precipitates, where interfacial chemical variations play significant roles. Here, we reveal that the coupling of solutes Ag, Cu and Li at the T1/Al interface results in the formation of Li-rich layers with different separations from the pre-existing T1 unit cell. Such Li-rich layers would template the thickening of T1 phase, and their different positions are identified to determine the thickening paths of different T1 phases. These findings provide insights that can benefit the modification of high-temperature performances of Al alloys via interface engineering.