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

Unlike conventional materials removal methods, additive manufacturing (AM) is based on a novel materials incremental manufacturing philosophy. Additive manufacturing implies layer by layer shaping and consolidation of powder feedstock to arbitrary configurations, normally using a computer controlled laser. The current development focus of AM is to produce complex shaped functional metallic components, including metals, alloys and metal matrix composites (MMCs), to meet demanding requirements from aerospace, defence, automotive and biomedical industries. Laser sintering (LS), laser melting (LM) and laser metal deposition (LMD) are presently regarded as the three most versatile AM processes. Laser based AM processes generally have a complex non-equilibrium physical and chemical metallurgical nature, which is material and process dependent. The influence of material characteristics and processing conditions on metallurgical mechanisms and resultant microstructural and mechanical properties of AM proc...

Laser additive manufacturing of metallic components: materials, processes and mechanisms

A study of the microstructural evolution during selective laser melting of Ti–6Al–4V

Selective Laser Melting (SLM) is a powder-based additive manufacturing process that has gained substantial interest in recent years due to its feasibility of producing geometrically- complex metallic components for end-use in various industries, with or without post-treatment procedures. This paper presents recent research undertaken on different scanning strategies and process parameters with the purpose of providing an overview of the achievable material performance of Ti6Al4V components, and comparing its properties with the conventionally-produced parts. In order to understand their output, differences in the building strategies of the systems studied are analysed, and their influence on the resulting mechanical and metallurgical properties is highlighted.

http://www.scielo.org.za/pdf/sajie/v27n3/16.pdf

On the impact of different system strategies on the material performance of selective laser melting-manufactured TI6AL4V components

Laser-assisted synthesis in CueAleNi system and some of its properties

Selective Laser Melting (SLM) has great potential in additive manufacturing methods because it allows producing full density complex parts with desired inner structure and surface morphology. Mechanical properties of SLM objects depend strongly on the material properties as well as strength of the connections between tracks and layers since all objects made by SLM are superposition of the single tracks and single layers. High temperature gradient as a result of the locally concentrated energy input can lead to residual stresses, crack formation and part deformations both during laser processing and after cutting objects from the substrate. X-ray diffraction method was used for investigation of residual stress in SLM samples from 316L steel fabricated by one-zone strategy with 50% overlap of the tracks. Samples had rectangular shape and different thickness: 50 m (one layer), 0.2 mm (5 layers) and 1 mm (25 layers). All as-made samples attached to the substrate had the tensile stress. Normal residual stress along the scan direction was 1.2-1.7 times higher than perpendicular direction. In some areas residual stress was about and exceeded the yield strength of 316L wrought material.

https://dr.ntu.edu.sg/bitstream/10356/84276/1/Evaluation%20of%20residual%20stress%20in%20selective%20laser%20melting%20of%20316L%20steel.pdf

Evaluation of Residual Stress in Selective Laser Melting of 316L Steel

Features of 3D printing, including laser melting of metal powders, were considered in this work. The effect of laser operation mode on the structure, residual stresses, and properties of manufactured metals was reviewed. A method for choosing process parameters using single tracks as universal for all types of metal laser 3D printers was proposed. Structural characteristics and medical requirements for biocompatible materials were presented. The biocompatible Ti–6Al–4V alloy manufactured by selective laser melting was considered.

Laser Additive 3D Printing of Titanium Alloys: Current Status, Problems, Trends

We have studied conditions for the synthesis of intermetallic phases in the Cu–Al–Ni system by selective laser sintering/melting, in particular by heating a powder mixture to 300°C. The effects of laser synthesis and heating on the microstructure of the intermetallic phases in the samples obtained have been studied using electron microscopy, optical metallography, and X-ray diffraction analysis. The results demonstrate high sinterability of stoichiometric mixtures. Resistivity measurements indicate that the samples exhibit a shape memory effect. We discuss the feasibility of producing biomicroelectromechanical systems using layerby- layer synthesis.

Igor Yadroitsev

Papers

On the impact of different system strategies on the material performance of selective laser melting-manufactured TI6AL4V components

Laser-assisted synthesis in CueAleNi system and some of its properties

Evaluation of Residual Stress in Selective Laser Melting of 316L Steel

Laser Additive 3D Printing of Titanium Alloys: Current Status, Problems, Trends

Layer-by-layer laser synthesis of Cu–Al–Ni intermetallic compounds and shape memory effect