Additively Manufacturable High-Strength Aluminum Alloys with Coarsening-Resistant Microstructures Achieved via Rapid Solidification.

Abstract

Additively manufactured aluminum (Al) alloys with high strength have broad industrial applications. Strength promotion necessitates a high-volume fraction of small, closely spaced precipitates to effectively impede dislocation motion. Here, it is shown that for certain compositions in the Al-Er-Zr-Y-Yb-Ni alloy class, L1₂-Al₃M phases, the primary strength contributor, can initially precipitate as submicron-scale (≈100 nm) metastable ternary phases under the rapid solidification of powder bed additive manufacturing; yet the subsequent coarsening-resistant L1₂-Al₃M phases that precipitate during heat treatment remain at the nanometer scale, imparting high strength. A candidate alloy is designed using hybrid calculation of phase diagrams (CALPHAD)-based integrated computational materials engineering (ICME) and Bayesian optimization algorithms. Powder is manufactured for this alloy and is additively manufactured into crack-free macroscale specimens with a strength that is five-fold that of the equivalent cast alloy and comparable to wrought Al 7075. After aging at 400 °C for 8 h, the room-temperature tensile strength reaches 395 MPa, which is 50% stronger than the best-known benchmark printable Al alloy. This integrated computational-experimental workflow shows the considerable potential to exploit rapid solidification in additive manufacturing to design alloys with commercially deployable properties.