Additive manufacturing of metallic components – Process, structure and properties

Freedom of design, mass customisation, waste minimisation and the ability to manufacture complex structures, as well as fast prototyping, are the main benefits of additive manufacturing (AM) or 3D printing. A comprehensive review of the main 3D printing methods, materials and their development in trending applications was carried out. In particular, the revolutionary applications of AM in biomedical, aerospace, buildings and protective structures were discussed. The current state of materials development, including metal alloys, polymer composites, ceramics and concrete, was presented. In addition, this paper discussed the main processing challenges with void formation, anisotropic behaviour, the limitation of computer design and layer-by-layer appearance. Overall, this paper gives an overview of 3D printing, including a survey on its benefits and drawbacks as a benchmark for future research and development.

Additive manufacturing (3D printing): A review of materials, methods, applications and challenges

Additive manufacturing of metals

Many traditional approaches for strengthening steels typically come at the expense of useful ductility, a dilemma known as strength-ductility trade-off. New metallurgical processing might offer the possibility of overcoming this. Here we report that austenitic 316L stainless steels additively manufactured via a laser powder-bed-fusion technique exhibit a combination of yield strength and tensile ductility that surpasses that of conventional 316L steels. High strength is attributed to solidification-enabled cellular structures, low-angle grain boundaries, and dislocations formed during manufacturing, while high uniform elongation correlates to a steady and progressive work-hardening mechanism regulated by a hierarchically heterogeneous microstructure, with length scales spanning nearly six orders of magnitude. In addition, solute segregation along cellular walls and low-angle grain boundaries can enhance dislocation pinning and promote twinning. This work demonstrates the potential of additive manufacturing to create alloys with unique microstructures and high performance for structural applications.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1443&context=ameslab_manuscripts

Additively manufactured hierarchical stainless steels with high strength and ductility

https://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=1037&context=mepubs

Additive manufacturing of Ti6Al4V alloy: A review

https://cmapspublic3.ihmc.us/rid=1P89G039W-1JGLLQJ-17GJ/DED%20Properties.pdf

Anisotropic tensile behavior of Ti-6Al-4V components fabricated with directed energy deposition additive manufacturing

Functionally graded material of 304L stainless steel and inconel 625 fabricated by directed energy deposition: Characterization and thermodynamic modeling

Laser-based additive manufacturing (AM) of metals using powder feedstock can be accomplished via two broadly defined technologies: directed energy deposition (DED) and powder bed fusion (PBF). In these processes, metallic powder is delivered to a location and locally melted with a laser heat source. Upon deposition, the material undergoes a rapid cooling and solidification, and as subsequent layers are added to the component, the material within the component is subjected to rapid thermal cycles. In order to adopt AM for the building of structural components, a thorough understanding of the relationships among the complex thermal cycles seen in AM, the unique heterogeneous and anisotropic microstructure, and the mechanical properties must be developed. Researchers have fabricated components by both DED and PBF from the widely used titanium alloy Ti-6Al-4V and studied the resultant microstructure and mechanical properties. This review article discusses the progress to date on investigating the as-deposited and heat-treated microstructures and mechanical properties of Ti-6Al-4V structures made by powder-based laser AM using DED and PBF.

Review of Mechanical Properties of Ti-6Al-4V Made by Laser-Based Additive Manufacturing Using Powder Feedstock

Refractory metal alloys such as tungsten and tantalum have long been primary materials of use in high temperature applications. The difficulty of processing tungsten and tantalum alloys makes the job of economically fabricating components from these alloys challenging. Furthermore, despite their intended use at elevated temperatures, limited research work has been to done to evaluate mechanical properties of these alloys at elevated temperatures. In this work, the mechanical properties of three tantalum alloys, pure Ta, Ta-10 vol%W, and Ta-10 vol%W-1.5 vol%TiC are studied using a range of mechanical testing procedures. Pure tantalum is found to display higher ductility at both room and elevated temperatures in comparison to alloyed samples. Addition of both 10 vol%W and 1.5 vol%TiC addition is found to result in comparable high-temperature strength and ductility in comparison to 10 vol%W addition, and improved hardness and flexural strength at room temperature. XRD and EDS analysis paired with microscopy of sintered materials and there fracture surfaces suggest this improvement is associated with solid solution strengthening occurring at Ta-W grain boundary regions. Analysis of sample fracture surfaces reveals indications of increased sample ductility at elevated temperatures for all alloys shown by tearing of tensile bar surfaces near the fracture regime and other ductile features.

Beth E. Carroll

Papers

Anisotropic tensile behavior of Ti-6Al-4V components fabricated with directed energy deposition additive manufacturing

Functionally graded material of 304L stainless steel and inconel 625 fabricated by directed energy deposition: Characterization and thermodynamic modeling

Review of Mechanical Properties of Ti-6Al-4V Made by Laser-Based Additive Manufacturing Using Powder Feedstock

Room and ultrahigh temperature mechanical properties of field assisted sintered tantalum alloys