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The number of available materials for Laser Powder Bed Fusion is still limited due to the poor processability of many standard alloys. In particular, the lack of high-strength aluminium alloys, widely used in aerospace and automotive industries, remains a big issue for the spread of beam-based additive manufacturing technologies. In this study, a novel high-strength aluminium alloy for high temperature applications having good processability was developed. The design of the alloy was done based on the chemical composition of the widely used EN AW 2618. This Al-Cu-Mg-Ni-Fe alloy was modified with Ti and B in order to promote the formation of TiB2 nuclei in the liquid phase able to stimulate heterogeneous nucleation of grains and to decrease the hot cracking susceptibility of the material. The new Al alloy was manufactured by gas atomisation and processed by Laser Powder Bed Fusion. Samples produced with optimised parameters featured relative density of 99.91%, with no solidification cracks within their microstructure. After aging, the material revealed upper yield strength and ultimate tensile strength of 495 MPa and 460 MPa, respectively. In addition, the alloy showed tensile strength higher than wrought EN AW 2618 at elevated temperatures. [ABSTRACT FROM AUTHOR]

In this research, steel alloys based on the Fe-Cr-Mo, Fe-Cr-Mn and Fe-Cr-Mo-Mn-Ni systems have been designed, produced by different atomisation techniques, and processed by laser powder bed fusion (L-PBF) to investigate their microstructural and mechanical behaviour. Both gas atomisation and water atomisation were considered for powder preparation. The resulting different flowability of powders, hence a different densification behaviour during processing, could be compensated by tuning the L-PBF parameters and by the application of a post treatment to improve flowability of the water atomised powders. In agreement with thermodynamic calculations, small-size oxide-based nonmetallic inclusions of the type SiO2, MnO-SiO2, Cr2O3-SiO2 were found within the steel matrix and on the fracture surfaces of the water atomised L-PBF alloys, featuring higher amounts of oxygen than the gas-atomised steels. Analyses on microstructure and hardness of the hardenable as-built steels suggested that during laser processing, the multilayer L-PBF structure undergoes an in-situ tempering treatment. Furthermore, the mechanical properties of the L-PBF steels could be widely tuned depending on the post-thermal treatment conditions. [ABSTRACT FROM AUTHOR]