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

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

Authors

S. Mohadeseh Taheri-Mousavi, Michael Xu, Florian Hengsbach, Clay Houser, Zhaoxuan Ge, Benjamin Glaser, Shaolou Wei, Mirko Schaper, James M. LeBeau, Greg B. Olson, A. John Hart

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.