Achieving high strength in laser powder-bed fusion processed AlFeCuZr alloy via dual-nanoprecipitations and grain boundary segregation

Abstract

• A novel crack-free and near-full dense Al-Fe-Cu-Zr alloy was designed for LPBF. • It exhibits heterogeneous microstructures with coarse-grain zones (CGZs) and fine-grain zones (FGZs). • (Al, Cu)Fe 3 nanoparticles precipitated in the CGZs, Fe and Cu co-segregated at the grain boundaries (GBs). • Al 3 Zr nanoparticles precipitated in the FGZs, Fe-rich nano-precipitates and Fe/Cu co-segregation appeared at GBs. • The as-printed AlFeCuZr alloy demonstrated a high yield strength of 500 MPa at room temperature and 163 MPa at 573 K. Additive manufacturing of aluminum alloys has received significant attention in the aerospace industry; however, achieving sufficient high strength, especially at elevated temperatures, remains challenging. Here, a crack-free and near-full dense Al-1Fe-0.6Cu-1.3Zr alloy was fabricated by the laser powder bed fusion (LPBF) technique. The Al-Fe-Cu-Zr alloy exhibits heterogeneous microstructures with two distinct zones. One is the so-called coarse-grain zones (CGZs) with an average grain size of 0.95 μm, where (Al, Cu)Fe 3 nanoparticles precipitate in the Al matrix and Fe and Cu cosegregate at the grain boundaries (GBs). The other is fine-grain zones (FGZs) with an average grain size of 0.45 μm, where an Al 3 Zr nanoparticle precipitates in each of the α-Al grains (serves as the nuclei), and Fe-rich nanoprecipitates and Fe/Cu cosegregation appear at the GBs. As a result, the LPBF Al-Fe-Cu-Zr alloy, with these unique heterogeneous structures, displays high strength at both room temperature and elevated temperatures, e.g., with high yield strengths of 500 MPa at room temperature, and 163 MPa at 573 K, both are higher than those of additive manufactured Al-based alloys reported thus far. It is suggested that the high strength over a wide temperature range of the current LPBF Al alloy is mainly attributed to the combination of the precipitation strengthening mechanism and grain-boundary strengthening mechanism.