Heat treatment response and mechanical properties of a Zr-modified AA2618 aluminum alloy fabricated by laser powder bed fusion
Marvin Schuster, Anthony De Luca, Dagmara Kucajda, E. Hosseini, Remo N. Widmer, Xavier Maeder, Christian Leinenbach
Abstract
Additive manufacturing of commercial materials designed for casting is challenging, particularly for hot-crack-susceptible alloys. Adding Zr to Al alloys has a positive effect on part consolidation by suppressing hot cracks and enabling nanoprecipitation hardening. Despite the special solidification conditions during laser powder bed fusion and the use of modified alloy chemistries, the heat treatments that were optimized decades ago for cast or wrought alloys are still applied. These treatments thus do not optimally exploit the full potential of novel alloys tailored for additive manufacturing. This work investigates the microstructure, precipitate formation, and mechanical properties of a Zr-modified 2618 Al alloy via laser powder bed fusion. A three-step heat treatment yields several nanometric phases, including L12-Al3Zr, S-Al2CuMg, and Mg2Si, which strengthen the alloy. Tensile tests reveal ultimate and yield strengths of 478 ± 7 MPa and 401 ± 3 MPa, respectively, and an elongation to fracture of 9.2 ± 1.1%. These values match conventionally manufactured and heat-treated 2618 standards and exceed T6 properties. The results emphasize the need to adapt heat treatments for additive manufacturing, not just materials.