What If Materials Could Think Ahead?

Abstract

Additive manufacturing (AM) has revolutionized how we shape matter, but perhaps more profoundly, how we must now think about materials. Traditionally, materials were designed to be shaped—cast, rolled, and extruded—and their properties fixed well before the part existed. In AM, this logic is no longer valid: matter is deposited, fused, or cured layer by layer, and properties emerge during the process. Microstructures become spatially heterogeneous; functionality evolves as a design parameter. This shift turns the old paradigm on its head. The goal is no longer to select materials that can tolerate the stresses of AM; the new challenge is to design materials that actively enable it. To fully exploit AM's potential, from lightweight, load-adaptive structures to multimaterial integration (heat-resistant), materials must become co-designers of the process.

This mindset sparked the German Priority Program SPP 2122 “Materials for Additive Manufacturing,” funded by the DFG (uni-due.de/matframe/). Launched in 2018, the program brought together researchers from powder metallurgy, polymer chemistry, materials modeling, and process engineering. Their shared goal is to establish a material-centric foundation for AM, spanning metal and polymer powder devalopment, theory and experiment, nanoscale control, and industrial relevance.

To build on this vision, the SPP 2122 began with a systematic state-of-the-art analysis of AM from a materials perspective. Two comprehensive reviews—one on metal-based^[1] and one on polymer-based^[2] feedstocks—mapped out the scientific landscape of laser powder bed fusion (L-PBF) over the past decade. The reviews identified the dominant materials (e.g., AlSi10Mg, PA12), prevailing process parameters, and emerging strategies such as nanoparticle additivation to overcome issues like anisotropy, cracking, or poor mechanical performance. By extracting and statistically analyzing material, process, and part properties across hundreds of studies, both works revealed that the future of L-PBF hinges on an integrated understanding of powder design, process control, and functional performance.

Complementing these reviews, a dedicated white paper laid the groundwork for a large-scale interlaboratory study (ILS) on powder bed fusion using a laser beam (PBF-LB) of metals and polymers.^[3] It highlighted the urgent need for standardized test methods and reliable metrics to assess nanoadditivated powders across the entire process chain. The white paper emphasized how nanoparticles affect not only flowability and absorption but also microstructure formation and mechanical properties, and proposed a data-rich framework based on the findable, accessible, interoperable, and reusable (FAIR)-principles and principal component analysis to reveal hidden correlations across the material-process-part continuum. These early efforts provided the conceptual and methodological backbone for many of the research activities in the PBF-LB community and directly informed the contributions now presented in this Special Issue.

Several contributions to this special issue focus on metal AM, where success depends on materials that not only withstand harsh thermal environments but also support process stability and functional properties. High-nitrogen steels (article number: 202402293) and eutectic aluminum alloys (article number: 202401665) show how tailored alloy design can control microstructure formation. Oxide-dispersion-strengthened steels (article numbers: 202402946 and 202500317) and in situ alloying (article number: 202402253) integrate microstructural tuning into the process itself. Magnesium-based alloys (article numbers: 202401322 and 202402704) underline how gas atmosphere and posttreatment influence final part behavior. The impact of contamination is addressed by Ellendt et al. in article number: 202401541, who showed that while fluid properties remain stable, microstructures change significantly in Fe-contaminated AlSi20 alloys, opening recycling perspectives. Tönjes et al. in article number: 202401542 complemented this view by showing that faster cooling rates in PBF-LB/M refine primary silicon phases in Al–Si alloys, directly improving hardness. These examples illustrate how AM-ready materials are no longer adapted from existing alloys but codeveloped with the process. Two additional studies push the material design envelope: Matthäus et al. (article number: 202500262) explored the AM processability of highly alloyed Al–Li systems, while Radtke et al. (article number: 202500885) compared powder metallurgy routes for high-nitrogen steels and their implications for mechanical performance and microstructure control.

In polymer AM, the challenges shift: control over crystallization, rheology of powder and melt, and thermal response become key. Luinstra et al. (article number: 202500426) addressed the preparation and thermal modification of disentangled ultrahigh-molecular-weight polyethylene (UHMWPE) particles. By tuning both synthesis and posttreatment steps, they demonstrate how tailored morphology and crystallinity can be leveraged to render UHMWPE powders processable by PBF-LB—a significant step forward for this otherwise challenging material class. In a complementary study, Luinstra et al. (article number: 202500536) examined the flow behavior of such polymers in AM, showing that disentanglement strategies can improve printability while preserving mechanical toughness. Their results indicate that direct energy deposition may offer a promising alternative to PBF for UHMWPE processing. Simulations of thermal accumulation and interlayer timing (article numbers: 202401285 and 202402206) provide frameworks to optimize polymer processing beyond trial-and-error. Together, these works signal a shift toward science-guided scaling of polymer AM.

A transformative movement within the SPP 2122 has been the use of nanoparticles as active enablers. Rather than being simple additives, they are deployed to tailor surface energy absorption, flowability, or interface stability. In a two-part study, Kwade et al. (article number: 202402297) and Sehrt et al. (article number: 202402296) showed how ceramic nanoparticle coatings alter both laser interaction and powder spreadability in stainless-steel powders. Grothe et al. in article number: 202401523 applied a Maillard-type surface chemistry to coat ceramic nanoparticles (NPs) with copper, bridging conductivity and compatibility. In polymers, Ziefuß et al. (article number: 202500466) compared surface sensitizers for diode-laser fusion of PA12, revealing how even subtle nanoparticle variations affect melting behavior. Wudy et al. (article number: 202500541) further expanded this materials–process interface by evaluating dielectric properties of semicrystalline thermoplastics, offering a route to link rheological and thermal behavior to energy coupling during PBF-LB/P. A striking example of nanoparticle functionality is provided by Gökce et al. in article number: 202401512, who demonstrated how silver nanoparticles in titanium form nanoislands with potent antibacterial properties, a promising route for biomedical AM. Jahns et al. (article number: 202401957) expanded this theme by embedding metalized nanoceramics into CuCrZr feedstocks, enabling oxide-dispersion strengthening without compromising conductivity. These contributions exemplify the growing recognition that the particle–process interface is a critical design space, and that nanostructures can be leveraged for macroscale functionality.

Several studies advance modeling and simulation as tools to predict and guide AM processes. Bierwisch et al. introduced in article number: 202401285 a finite-difference approach for analyzing heat accumulation and melt behavior in polymers. Döring et al. (article number: 202401958) developed a melt pool scaling law for metals with high thermal diffusivity. Leupold et al. (article number: 202402929) contributed a scan curve diagnostic that bridges geometry, energy input, and process performance. Deng et al. (article number: 202400305) modeled powder spreading homogeneity, while Rudloff et al. proposed in article number: 202402206 a dimensionless analysis of energy conversion. Together, these works represent a maturing effort to translate physical understanding into process predictability.

Zhuo et al. (article number: 202500702) executed a comparative study on thermal property measurements of steel powders. Such efforts highlight a simple but powerful insight: materials innovation in AM must be matched by measurement innovation. Postprocess reliability is also addressed by Kessler et al. in article number: 202501181, who systematically investigated the natural and artificial aging behavior of AlSi10Mg alloys after PBF-LB. The study highlights how microstructure and hardness evolve under different thermal histories and emphasizes the need for consistent posttreatment protocols to ensure reproducible mechanical performance.

A forward-looking strategy is outlined in the perspective by Lentz et al. in article number: 202402033, who proposed a powder-based pathway for high-nitrogen steels involving Si₃N₄ shell–core particles that release nitrogen during hot isostatic pressing  consolidation. This approach, though developed for powder metallurgy, outlines concepts for AM-compatible alloy development where reactivity and processing are coengineered from the start.

One of the most comprehensive and collaborative efforts of the SPP 2122 is an unparalleled, large-scale ILS (article number: 202402930), designed not merely to assess reproducibility, but to systematically explore the influence of novel, nanoparticle-modified materials across different AM platforms (Figure 1). Unlike conventional round robin tests focused solely on repeatability, this study was conceived to uncover robust, generalizable structure–property–process relationships in L-PBF (PBF-LB).

The study spans both metal (AlSi10Mg and variants) and polymer (PA12 and variants) PBF-LB systems, each complemented by two nanoadditivated powders, resulting in six distinct material systems. These nanodoped feedstocks embody the program's core ambition to move beyond legacy materials and instead develop new powders explicitly designed for laser-based AM. Each material–process combination was investigated across multiple laboratories using harmonized experimental procedures and comprehensive characterization protocols. More than 30 institutions contributed, producing over 1,400 structured measurements across powder, process, and part levels. All data were collected and curated in accordance with FAIR principles, ensuring findability, accessibility, interoperability, and reusability. This effort yielded one of the most extensive datasets in the field of AM. By integrating these measurements into a unified data structure, the study enables cross-scale analysis of over 1.2 million parameter correlations. These correlations capture how powder properties, process parameters, and nanoparticle modifications interact to influence microstructure and part performance. Rather than providing static benchmark values, the open-access dataset^[4] offers a dynamic foundation for understanding and predicting AM behavior across materials classes and represents a blueprint for future large-scale, data-driven materials research.

Together, the contributions in this special issue, entitled materials for AM, do more than showcase scientific progress, they reflect a fundamental shift in how materials and processes are developed, not in isolation, but in close interaction from the earliest stages of the process chain. This integrated approach was at the heart of SPP 2122. Rather than adapting decades-old powders to new laser technologies, the program promoted coordinated research into materials that are specifically designed for laser-based AM. By uniting expertise in photonics and material science, and by fostering tandem projects across material classes and process technologies, SPP 2122 helped establish a new paradigm: one in which material development is not an afterthought, but a central, enabling force in the advancement of AM.