Additively manufactured fine-grained ultrahigh-strength bulk aluminum alloys with nanostructured strengthening defects

Abstract

In response to the critical need for lightweight designs and carbon neutrality, we introduce an innovative additively manufactured ultrafine-grained Al-Mg-Mn-Sc-Zr alloy reinforced with nano-structured planar defects via laser powder bed fusion (L-PBF), developed for complex-shaped parts that demand high strength and superior ductility. Owing to the uneven distribution of the L1₂-ordered Al₃(Sc, Zr) nanoparticles, the as-printed alloy demonstrates a hierarchically heterogeneous microstructure featuring a triple-modal grain distribution. Tailored planar defects comprising stacking faults, 9R phase and nanotwins are strategically introduced in the as-printed alloy. Beyond the nano-scaled planar defects and the triple-modal grain distribution, further direct ageing process augments the abundance of nanoprecipitates, collectively boosting the yield strength to 656 MPa, which is higher than almost all L-PBFed Al alloys hitherto reported, and a decent ductility of 7.2 %. This work paves the way for the near net shape forming of high-performance Al alloy components for advanced structural applications.