Laser-based powder bed fusion enables the additive manufacturing of high-quality metal components. Beyond extending its applicability to new materials, current research increasingly focuses on process control to ensure consistent and predictable mechanical performance. Precipitation-hardenable alloys such as 15-5PH are attracting growing interest owing to their high strength, stiffness, and corrosion resistance. Previous studies have predominantly addressed microscopic and macroscopic analyses, with particular emphasis on porosity, its impact on mechanical properties, and the effects of various post-processing heat treatments. However, thermal properties and dimensional accuracy, both dependent on the applied process parameters, are of considerable relevance for the subsequent applicability, as they exert a decisive influence on component design. In this context, the present work examines the mechanical and thermal properties obtained under varying laser powers and scanning speeds, and compares these with the achievable dimensional accuracy using a plate-based SC-BCC structure as an example. The objective is to identify a process window that achieves a compromise between high dimensional accuracy and desirable mechanical properties. The results demonstrate that low energy densities yield high dimensional accuracy but also high porosity, which degrades both mechanical and thermal performance. In contrast, high energy densities result in high mechanical properties but compromise dimensional accuracy due to increased distortion during processing. Within the investigated process window, a favorable compromise between dimensional accuracy and the resulting mechanical and thermal properties of 15-5PH was identified. These findings contribute to a deeper understanding of the process–property relationships and highlight limitations relevant to future applications.

Abstract Understanding how molecular weight distribution (MWD) influences the mechanical and fracture behaviour of additively manufactured PA12 is essential for establishing reliable process–structure–property relationships. An approach to minimize anisotropy has been to specifically target the feedstock materials with the goal of enhancing interlayer adhesion. In this study, polyamide 12 (PA12) grades of MWD were investigated to determine the effect of MWD on the interlayer bond formation and anisotropy of the printed samples. Three different grades of PA12 were printed into tensile coupons and double cantilever beam (DCB) specimens and the mechanical properties were assessed to study interlayer bond strength using standard fracture toughness technique. A significant improvement in mechanical properties and fracture toughness were observed with higher print temperatures attributed to strong interlayer adhesion owing to longer interlayer bonding times (verified through the Lumped Capacity model and thermocouple data). Fracture toughness assessment also demonstrated that amongst samples printed at the same temperature, PA12 with a lower average MWD provided the highest fracture toughness (G 1C ) values, attributed to the faster diffusion of short polymer chains across the interlayer interface. Tailoring the MWD of feedstock polymers utilized in 3D printing as a strategy to optimize performance and lower anisotropy was demonstrated to be a feasible pathway. These findings were utilized by developing a PA12 blend of broad MWD which provided the highest overall mechanical properties and G 1c , demonstrating the usefulness of incorporating a high proportion of fast diffusing short polymer chains in the development of polymeric feedstock materials. Additionally, for large scale 3D printing applications, where maintaining high chamber temperatures is impractical, these results suggest that optimizing MWD can be an alternative strategy to improve interlayer adhesion and mechanical properties without relying solely on elevated print temperatures.

Abstract Medium entropy alloys (MEAs) with multiphase microstructure offer a promising combination of strength and ductility. Identifying potential compositions for additive manufacturing from a huge compositional domain is challenging. CALPHAD based Thermo-Calc ® simulations are carried out to identify potential compositions; three alloys are selected within the ternary Fe–Ni–Nb MEA system, to explore hypo and hyper eutectic conditions. The solidification pathway is simulated using Scheil’s model with solute trapping at different solidification velocities for in-situ alloying in Laser Powder Bed Fusion (PBF-LB/M), predicting FCC and Laves phases to be present based on the Nb content and laser scan speed. The results were validated through single-track experiments and Energy-dispersive X-ray spectroscopy (EDS) Despite its high melting point, Nb was successfully alloyed with the Fe and Ni powders. The Key-hole mode and remelting proved effective to increase intermixing of the elements. Most uniform distribution of elements was observed in hypo eutectic compositions, which confirms the in-situ alloying strategy adopted for fine tuning the multicomponent compositions. Cracking in the weld tracks was observed in hyper eutectic compositions due to the primary Laves phase formation. Finally, High-speed ratio pyrometry was applied to monitor the thermal history during laser-material interaction and calculate the apparent cooling rates, which ranged between the 10 4 and 10 6 °C/s. The combined experimental and computational approach provides a foundation for controlled in-situ alloying in the Fe–Ni–Nb system and predictive alloy design. The current study confirms simulation-guided additive manufacturing for the development of tailored medium entropy alloys.