A high-strength and thermally stable TiB2-modified Al-Mn-Mg-Er-Zr alloy fabricated via selective laser melting

To increase the processability and plasticity of the selective laser melting (SLM) fabricated Al-Mn-Mg-Er-Zr alloys, a novel TiB2-modified Al-Mn-Mg-Er-Zr alloy with a mixture of Al-Mn-Mg-Er-Zr and nano-TiB2 powders was fabricated via SLM. The processability, microstructure, and mechanical properties of the alloy were systematically investigated by density measurement, microstructure characterization, and mechanical properties testing. The alloys fabricated at 250 W displayed higher relative densities due to a uniformly smooth top-surface and appropriate laser energy input. The maximum relative density value of the alloy reached 99.7±0.1%, demonstrating good processability. The alloy exhibited a duplex grain microstructure consisting of columnar regions primarily and equiaxed regions with TiB2, Al6Mn, and Al3Er phases distributed along the grain boundaries. After directly aging treatment at a high temperature of 400 °C, the strength of the SLM-fabricated TiB2/Al-Mn-Mg-Er-Zr alloy increased due to the precipitation of the secondary Al6Mn phases. The maximum yield strength and ultimate tensile strength of the aging alloy were measured to be 374 ± 1 MPa and 512 ± 13 MPa, respectively. The SLM-fabricated TiB2/Al-Mn-Mg-Er-Zr alloy demonstrates exceptional strength and thermal stability due to the synergistic effects of grain growth inhibition and the incorporation of TiB2 nanoparticles and secondary Al6Mn precipitates.