Dependence of mechanical properties and microstructure on solidification onset temperature for Al2024–CaB6 alloys processed using laser powder bed fusion

The addition of a sufficient amount the potent heterogeneous nucleating agent CaB6 enables fabrication crack-free specimens from solidification-crack susceptible high-strength 2024 (Al–Cu–Mg) aluminum (Al) alloy using laser powder bed fusion (LPBF). present work investigates effects varying contents nanoparticles (0.0–2.0 wt%) on alloys' solidification behavior as well specimens’ volume, microstructure, and mechanical properties. findings X-ray microscopy (XRM) analyses LPBF in-situ differential fast scanning calorimetry (DFSC) single particles at LPBF-like high heating cooling rates reveal decreasing crack volumes with supercooling. A content equal to or greater than 0.5 wt% effectively suppresses cracking. 1.0 is defined optimum in terms With this an average grain size 0.77 μm, ultimate tensile strength (UTS) 478 ± 4 MPa elongation (A) 13.2 0.1% are achieved. When further increased, alloy's asymptotically approaches minimum ∼0.7 μm for given process parameters. This value corresponds nucleation-free zone (NFZ), within which not activated agents, resulting deposition along boundaries.