Study on thermal stability of 2519(Sc) Al alloy and establishment of coarsening model

The rapid development of aerospace and military fields puts higher demands on the thermal stability of aluminum alloys. In this paper, the strengthening mechanism of thermal stability of 2519 alloy was investigated by Sc microalloying, and the coarsening model of precipitates was established. The results show that the Sc-containing alloy exhibited excellent high-temperature properties at 300 °C, with yield strength (YS) and ultimate tensile strength (UTS) of 160.8 MPa and 177.2 MPa, an increase of 6.5% and 6.0%, respectively. The YS and UTS of the Sc-containing alloy reached 217.3 MPa and 291.4 MPa at 250 °C/1000 h of thermal exposure, which were improved by 9.6% and 34.1%, respectively. The reason was that the Sc atoms were segregated at the Al/θ′ interface, which led to the slow diffusion kinetics of θ′ at high temperature and suppressed the coarsening of the θ′ phase, thus improving the thermal stability performance of the Sc-containing alloy. Furthermore, the θ′ phase in 2519(Sc) alloy followed the LSW coarsening model, while the segregation of Sc in the θ′ phase can reduce the interfacial energy and thus the coarsening rate of the θ′ phase.