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

Abstract

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.

摘要

第三代铝锂合金(Al–Cu–Li合金)在航空航天领域应用广泛, 但服役温度一般低于100°C. 本研究中, 我们提出了一种提高Al–Cu–Li合金在200–300°C下耐热性的新思路, 即通过添加微量的Sc和Si元素, 当T1相在热暴露过程中溶解后, 促进θ′相的形核析出. 在200–300°C的热暴露过程中, Sc和Si微合金化的Al–Cu–Li合金中有大量的纳米θ′相析出, 并具有高的热稳定性, 相反, 无微合金化的Al–Cu–Li合金中的θ′相则迅速粗化. Sc和Si微合金化的Al–Cu–Li合金在300°C下的抗拉强度为155 MPa, 延伸率为9.2%. 因此, Sc和Si微合金化的Al–Cu–Li合金在200–300°C下的耐热性显著提高, 与商用耐热铝合金2618和2219相比, 具有更优异的高温强度和比强度.