High strength and fatigue performance achieved for L-PBF processed hybrid particle reinforced Al-Cu-Mg composite

This study highlights the successful manufacturing of a crack-free, dense, hybrid ex-situ/in-situ particle reinforced (Ti + B4C)/Al-Cu-Mg composite, fabricated by laser powder bed fusion and exhibiting exceptional mechanical performance. In its as-built (AB) state, the composite displays a unique microstructure characterized by equiaxed grains with an average grain size of 1.0 +/- 0.3 mu m, notable interdendritic microsegregation of Cu, Mg, Mn, and Fe, randomly distributed ex-situ added Ti and B4C particles featuring a surface interaction layer with the metal matrix, and in-situ formed reinforcing particles, such as TiB2 and TiC. After subjecting the material to hot isostatic pressing (HIP) and subsequent aging treatment, dissolution of interdendritically segregated elements occurs, and precipitation of Al2Cu, Al12Mg17, and Al-Fe-Cu-Mn phases is observed. Significantly enhanced fatigue performance is recorded, reaching to 107 cycles at 250 MPa in AB and 330 MPa in HIP state, marking a 32 % improvement. The current study highlights the intricate relationship between the different microstructural features in AB and HIPed state, leading to fracture during tensile and fatigue loading conditions.