Al-Cu-Ce(-Zr) alloys with an exceptional combination of additive processability and mechanical properties

Abstract

High-temperature Al-9Cu-6Ce and Al-9Cu-6Ce-1Zr (wt%) alloys were designed for fabrication with laser powder bed fusion additive manufacturing (AM). An ultra-fine eutectic structure comprising FCC-Al and particles of a previously unidentified Al8Cu3Ce intermetallic phase was obtained with an inter-particle spacing of approximately 280 nm. The inherent hot-tearing resistance of the eutectic alloys resulted in > 99.5% relative density. A thermodynamic model suggested improved hot-tearing resistance of the present alloys relative to the benchmark AM AlSi10Mg alloy. The Al-Cu-Ce alloy exhibited superior thermal stability with approximately 75% of the as-fabricated hardness retained after 200 h exposure at 400 °C, owed to the coarsening resistance of the intermetallic particles. The Al-Cu-Ce-Zr alloy age-hardened through precipitation of nanoscale Al3Zr precipitates. The aged microstructure was stable at 350 °C with a 13% higher hardness after 200 h exposure compared to the as-fabricated condition. The combined influence of ultra-fine spacing and coarsening resistance of the intermetallic particles resulted in the higher yield strength of the Al-Cu-Ce and Al-Cu-Ce-Zr alloys compared to AM AlSi10Mg and Scalmalloy at temperatures greater than 200 °C. This work essentially demonstrates that thermally stable Al alloys with exceptional mechanical properties can be produced by additive manufacturing.