• Letofsky-Papst, Ilse
• Mair, Philipp
• Weinberger, Nikolaus
• Rainer, Tobias
• Leichtfried, Gerhard
• Goettgens, Valerie Sue
• Mitsche, Stefan

Abstract

<p>The 2024 aluminum alloy (Al-Cu-Mg) is widely used in aerospace; however, due to its solidification-cracking tendency, its processability using laser powder bed fusion (LPBF) remains a critical issue. The addition of 2 wt% CaB₆ nanoparticles induces a columnar-to-equiaxed transition (CET), resulting in an immediate improvement in LPBF processability. High-density (&gt;99.5%) and crack-free specimens, with a homogeneous equiaxed microstructure and without preferred grain orientation, were obtained. The small average α-Al grain size of 0.91 ± 0.32 µm is attributed to the similar lattice constants of Al and CaB₆ facilitating Al nucleation on CaB₆ nanoparticles, resulting in a highly coherent Al/CaB₆ interface. CaB₆ nanoparticles act as heterogeneous nucleus and exert a pinning force on the grain boundaries, which reduces grain coarsening. The as-built specimens exhibit both high-yield strength (348 ± 16 MPa) and high-tensile strength (391 ± 22 MPa), combined with a high total elongation at break (12.6 ± 0.6%). The macro hardness amounts to 132 ± 4 HV₅.</p>

Topics

• nanoparticle
• density
• impedance spectroscopy
• grain
• grain size
• aluminium
• crack
• strength
• hardness
• selective laser melting
• yield strength
• tensile strength
• solidification