Additive manufacturing of metallic components – Process, structure and properties

Additive manufacturing of metals

An introduction to heat transfer

Selective Laser Melting (SLM) is a particular rapid prototyping, 3D printing, or Additive Manufacturing (AM) technique designed to use high power-density laser to melt and fuse metallic powders. A component is built by selectively melting and fusing powders within and between layers. The SLM technique is also commonly known as direct selective laser sintering, LaserCusing, and direct metal laser sintering, and this technique has been proven to produce near net-shape parts up to 99.9% relative density. This enables the process to build near full density functional parts and has viable economic benefits. Recent developments of fibre optics and high-power laser have also enabled SLM to process different metallic materials, such as copper, aluminium, and tungsten. Similarly, this has also opened up research opportunities in SLM of ceramic and composite materials. The review presents the SLM process and some of the common physical phenomena associated with this AM technology. It then focuses on the following a...

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Review of selective laser melting : materials and applications

This article reviews published data on the mechanical properties of additively manufactured metallic materials. The additive manufacturing techniques utilized to generate samples covered in this review include powder bed fusion (e.g., EBM, SLM, DMLS) and directed energy deposition (e.g., LENS, EBF3). Although only a limited number of metallic alloy systems are currently available for additive manufacturing (e.g., Ti-6Al-4V, TiAl, stainless steel, Inconel 625/718, and Al-Si-10Mg), the bulk of the published mechanical properties information has been generated on Ti-6Al-4V. However, summary tables for published mechanical properties and/or key figures are included for each of the alloys listed above, grouped by the additive technique used to generate the data. Published values for mechanical properties obtained from hardness, tension/compression, fracture toughness, fatigue crack growth, and high cycle fatigue are included for as-built, heat-treated, and/or HIP conditions, when available. The effects of test...

Metal Additive Manufacturing: A Review of Mechanical Properties

https://dr.ntu.edu.sg/bitstream/10356/88603/1/Anisotropy%20and%20heterogeneity%20of%20microstructure%20and%20mechanical%20properties%20in%20metal%20additive%20manufacturing-%20A%20critical%20review.pdf

Anisotropy and heterogeneity of microstructure and mechanical properties in metal additive manufacturing: A critical review

Graded microstructure and mechanical properties of additive manufactured Ti–6Al–4V via electron beam melting

As an important metal three-dimensional printing technology, electron beam melting (EBM) is gaining increasing attention due to its huge potential applications in aerospace and biomedical fields. EBM processing of Ti-6Al-4V as well as its microstructure and mechanical properties were extensively investigated. However, it is still lack of quantitative studies regarding its microstructural evolution, indicative of EBM thermal process. Here, we report α' martensitic transformation and α/β interface evolution in varied printing thicknesses of EBM-printed Ti-6Al-4V block samples by means of atom probe tomography. Quantitative chemical composition analysis suggests a general phase transformation sequence. By increasing in-fill hatched thickness, elemental partitioning ratios arise and β volume fraction is increased. Furthermore, we observe kinetic vanadium segregation and aluminum depletion at interface front and the resultant α/β interface widening phenomenon. It may give rise to an increased α/β lattice mismatch and weakened α/β interfaces, which could account for the degraded strength as printing thickness increases.

/pdf/revealing-martensitic-transformation-and-a-b-interface-oa6n13ouzz.pdf

Revealing martensitic transformation and α/β interface evolution in electron beam melting three-dimensional-printed Ti-6Al-4V.

https://dr.ntu.edu.sg/bitstream/10220/26154/1/Accepted%20Manuscript.pdf

An experimental and simulation study on build thickness dependent microstructure for electron beam melted Ti–6Al–4V

An industrial impeller has been successfully fabricated by using Ti-6Al-4V extra low interstitial (ELI) powder via an Arcam A2XX electron beam melting (EBM®) machine. With the introduction of the A2XX, Arcam allowed the production of complex large-scale parts for industrial applications. However, the implementation of as-built metallic additive manufacturing (AM) parts in the industry is still far from straightforward and requires a sound understanding of the processing and the material properties of as-built part. This study examines the EBM thermal process influencing the microstructure evolution of Ti-6Al-4V by the EBM process. Ti-6Al-4V blocks with varying thicknesses were fabricated to simulate the different thickness of complex parts. The microstructure and Vickers hardness were evaluated. This paper mainly contributes to the EBM manufacturing of the industrial impeller and the build thickness dependence of microstructure and mechanical properties in EBM additive manufactured Ti-6Al-4V.

Yihong Kok

Papers

Anisotropy and heterogeneity of microstructure and mechanical properties in metal additive manufacturing: A critical review

Graded microstructure and mechanical properties of additive manufactured Ti–6Al–4V via electron beam melting

Revealing martensitic transformation and α/β interface evolution in electron beam melting three-dimensional-printed Ti-6Al-4V.

An experimental and simulation study on build thickness dependent microstructure for electron beam melted Ti–6Al–4V

Fabrication and microstructural characterisation of additive manufactured Ti-6Al-4V parts by electron beam melting