Achieving strength-ductility balance in a laser powder bed fusion fabricated TiB2/Al-Cu-Mg-Ag alloy

A crack-free, strong and ductile Al-Cu-Mg-Ag alloy with TiB2 particles was successfully fabricated with laser powder bed fusion (L-PBF). Subsequent solution and aging were designed to modify the microstructure and strengthen the alloy. The as-fabricated alloy achieved an isotropic microstructure consisting of random-orientated and equiaxed grains with an average grain size of about 1.15 mu m. The role of TiB2 particles in reducing metallurgical defects (such as hot cracking) and enhancing mechanical performance of the alloy was revealed by multi-scale advanced microstructural characterizations. This benefits from the formation of two-dimensional compounds of Al3Ti on the terminated (0001)TiB2 plane, which could reduce the lattice mismatch, alter the potency of TiB2 particles, and refine the grains. The as-built alloy shows an excellent combination of strength and ductility with a yield strength (YS) of 289 +/- 5.7 MPa, ultimate tensile strength (UTS) of 390 +/- 6.5 MPa, and elongation to failure (El) of 14.8 +/- 1.8%. After the heat treatment, high-density of theta', Omega', and Omega phases were precipitated, significantly improving the YS to 405 +/- 3.2 MPa and UTS to 470 +/- 3.5 MPa, while slightly decreasing the El to 11.6 +/- 0.9%. The strengthening mechanisms are quan-titatively evaluated and the plastic instability phenomenon (Luders band and Portevin-Le-Chatelier effect) of the as-built alloy was also analyzed.(c) 2023 Elsevier B.V. All rights reserved.