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AM Materials ≠ Traditional Materials
AM Materials ≠ Traditional Materials
Traditional manufacturing relied on standardized materials, often in bulk form, such as metal billets, polymer pellets, or ceramic powders, tailored for processes like casting, forging, and injection molding.
Additive manufacturing spurred the development of novel material formulations, such as photopolymer resins for SLA, thermoplastic filaments for FDM, or metal powders with specific particle size distributions for SLS or DMLS (Direct Metal Laser Sintering).
Fundamental Differences in Material Formulation and Behavior:
Material Behavior under AM Conditions: AM materials experience rapid heating and cooling, which can affect phase transformations in metals or crystallinity in polymers. Understanding these behaviors is crucial for predicting final part properties.
Additives and Fillers: To enhance material properties or processability, AM materials might include additives or fillers, such as carbon fibers in polymers for increased strength or flow enhancers for better powder spreading in powder bed fusion processes.
Material Anisotropy: Due to the layer-by-layer nature of AM, materials can exhibit anisotropy, or directional dependence of properties. This is distinct from bulk materials that are often isotropic due to their processing methods.
Material Variety and Properties:
Wide Range of Materials: AM isn't limited to just metals or polymers. There's an expanding list that includes ceramics, composites, and even biomaterials, each offering unique properties for specialized applications.
Tailoring Properties: The ability to mix materials, especially in processes like multi-material jetting or material extrusion, allows for parts with gradient properties or even embedding electronics within parts.
AM Process-Property Characteristics
AM Process-Property Characteristics
The intricate relationship between additive manufacturing processes and the resulting material properties is pivotal. Factors inherent to each AM process can greatly influence the microstructure, mechanical strength, surface finish, and other vital properties of the end product.
AM Processes and Material Interplay:
FDM (Fused Deposition Modeling): By extruding melted thermoplastic filament layer-by-layer, properties like layer adhesion, material strength, and surface finish are influenced by parameters such as extrusion temperature, layer height, and nozzle diameter.
SLA (Stereolithography): Utilizing UV light to cure liquid resins, SLA can achieve high-resolution parts. Factors like light intensity and exposure time play pivotal roles in determining material properties, such as rigidity and tensile strength.
SLS (Selective Laser Sintering): In this powder bed fusion process, a laser selectively sinters powder material, forming solid parts. Here, laser power and scan speed are crucial in defining bond strength, part density, and overall mechanical properties.
Microstructural Evolution:
Rapid heating and cooling rates, as well as layer-by-layer deposition, lead to unique microstructures in AM parts. Understanding these transformations is crucial, as it can influence material strength, ductility, and other physical properties.
Residual Stresses: The rapid solidification in AM can lead to internal stresses which, if not managed, can result in warping, cracking, or even part failure.
Post-processing Impact: Heat treatments, surface treatments, or other post-processes can alter or optimize the microstructure, further tailoring the final material properties.
Material Variety and Customizability:
Multi-material AM: The capability to deposit multiple materials in a single build, leading to parts with region-specific properties or functionalities.
Custom Properties through Process Control: Leveraging AM process parameters to derive specific material attributes or responses.
AM Material Design, Classification, & Research
AM Material Design, Classification, & Research
Ongoing research in the domain of AM materials focuses on developing novel materials, refining existing ones, and enhancing their compatibility with various AM techniques.
Material Design for Additive Manufacturing:
Functional Gradients: AM's unique ability to create parts with varying material compositions throughout their geometry. This means one can design a part that has varying mechanical, thermal, or electrical properties.
Reactive Materials: Designing materials that can respond or change properties during the AM process. For example, materials that harden upon exposure to specific wavelengths of light or heat.
Custom Alloys and Composites: Traditional manufacturing often relies on standardized alloys, but AM offers the possibility to design custom alloys or composite materials tailored for specific properties or applications.
Classification of AM Materials:
Metallics: Such as titanium, stainless steel, and nickel alloys. Used in processes like DMLS, SLS, or Electron Beam Melting (EBM).
Polymers: These can be thermoplastics (like ABS, PLA, or nylon) or thermosets (like photopolymer resins). Used in FDM, SLA, and PolyJet printing.
Ceramics: Materials like zirconia or alumina that are processed using binder jetting or specialized SLA processes.
Composites: Combinations of the above materials, often enhanced with fibers or particles for improved properties. For example, carbon fiber-reinforced polymers.
Biomaterials: Designed for medical or biotechnological applications, these materials can be compatible with living tissue, and can include hydrogels or even cell-laden matrices for bioprinting.
Research and Future Directions in AM Materials:
Emerging Materials: Research into new materials like high-entropy alloys, self-healing polymers, or materials with unique microstructures tailored for AM.
Standardization and Testing: As AM becomes more prevalent, there's ongoing research into standardizing material properties and testing methods to ensure reliability and repeatability.
Post-Processing and Treatment: Research on how to enhance AM material properties post-production. This includes techniques like heat treatments, infiltration, or coatings to enhance durability, surface finish, or other properties.
Sustainability: Investigating the recyclability and environmental impact of AM materials, aiming to make additive manufacturing more sustainable in the long run.
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