Improving heat resistance of Al–Cu–Li alloy with the addition of Sc and Si

Al–Cu–Li alloys are important third-generation aluminum–lithium alloys in the aerospace field; however, they suffer from a service temperature below 100°C. In this work, we propose a new strategy for improving the heat resistance of Al–Cu–Li alloys at 200–300°C by promoting the nucleation of θ′ precipitates after dissolving T1 precipitates during thermal exposure with the minor addition of Sc and Si. During thermal exposure at 200–300°C, numerous nanoprecipitates of θ′ nucleate after dissolving some T1 precipitates in the minor-alloyed Al–Cu–Li alloy with Sc and Si, exhibiting high thermal stability. By contrast, the θ′ phase rapidly coarsens in the Al–Cu–Li alloy in the absence of Sc and Si additions. The minor-alloyed Al–Cu–Li alloy has a tensile strength of ~154 MPa and elongation of 9.2% at 300°C. Therefore, the heat-resistance performance of Al–Cu–Li alloy with Sc and Si microalloying is enhanced at 200–300°C, exhibiting considerable progress in both high-temperature strength and specific strength compared with those of commercial heat-resistant 2618 and 2219 alloys.