Thermodynamic-driven multi-objective alloy design strategy for laser powder bed fusion of Aluminum alloys.

The adoption of Laser Powder Bed Fusion (L-PBF) for aerospace-grade aluminum (Al) alloys is slowed down by susceptibility to hot & cold cracking, porosity formation, low build rates (~30cm3/h) and difficulty in controlling microstructure. Even alloys specifically designed for L-PBF, such as Scancromal® (Al–Cr–Sc–Zr), require further optimization. This study utilizes an Integrated Computational Materials Engineering (ICME) framework, powered by thermodynamic simulations (ThermoCalc®) and coupled with data-driven optimization strategies, to systematically improve Scancromal®-type alloys. The optimization targets alloy composition (varying Cr, Sc, Zr, Mo content) and key process parameters (laser power, scanning speed, layer thickness). To mitigate cracking & lack of fusion/keyhole porosities for high build rate condition (~90cm3/h) of Scancromal®, a multi objectives optimization approach on the composition and process parameters is proposed. The different criteria were used as objectives to optimize : Rappaz, Drezet & Gremaud (RDG) model for minimizing hot cracking, Fourier Number to mitigate cold cracking and printability maps to minimize porosities. The first input used for computing different criteria rely on the solidification path computed using the Scheil-Gulliver assumption taking into account the solute trapping that is representative of high cooling rates of L-PBF. Secondly, thermal gradients, solidification velocities & melt pool dimensions linked to process parameters were extracted from steady state simulations performed in the additive manufacturing module of Thermocalc®. Finally, several multi-objective optimization techniques were explored such as Bayesian Optimization with Gaussian Process Regressors, Genetic Algorithms including but not limited to Non-dominated Sorting Genetic Algorithm (NSGA) and Multi-Objective Particle Swarm Optimizer (MOPSO) algorithms in order to find promising alloys with regards to all criteria. The approach proposed in this study, provides guidelines to design Al-alloys and their process space for laser powder bed fusion.