Additive manufacturing of metallic components – Process, structure and properties

Mechanical alloying (MA) is a solid-state powder processng technique involving repeated welding, fracturing, and rewelding of powder particles in a high-energy ball mill. Originally developed to produce oxide-dispersion strengthened (ODS) nickel- and iron-base superalloys for applications in the aerospace industry, MA has now been shown to be capable of synthesizing a variety of equilibrium and non-equilibrium alloy phases starting from blended elemental or prealloyed powders. The non-equilibrium phases synthesized include supersaturated solid solutions, metastable crystalline and quasicrystalline phases, nanostructures, and amorphous alloys. Recent advances in these areas and also on disordering of ordered intermetallics and mechanochemical synthesis of materials have been critically reviewed after discussing the process and process variables involved in MA. The often vexing problem of powder contamination has been analyzed and methods have been suggested to avoid/minimize it. The present understanding of the modeling of the MA process has also been discussed. The present and potential applications of MA are described. Wherever possible, comparisons have been made on the product phases obtained by MA with those of rapid solidification processing, another non-equilibrium processing technique.

Mechanical Alloying And Milling

Principles of equal-channel angular pressing as a processing tool for grain refinement

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

Selective laser melting of iron-based powder

Purpose – This paper provides an overview of the different binding mechanisms in selective laser sintering (SLS) and selective laser melting (SLM),
thus improving the understanding of these processes. Design/methodology/approach – A classification of SLS/SLM processes was developed, based on the binding mechanism occurring in the process, in
contrast with traditional classifications based on the processed material or the application. A broad range of commercial and experimental SLS/SLM
processes – found from recent articles as well as from own experiments – was used to explain the different binding mechanism categories.
Findings – SLS/SLM processes can be classified into four main binding mechanism categories, namely “solid state sintering”, “chemically induced
binding”, “liquid phase sintering – partial melting” and “full melting”. Most commercial processes can be classified into the latter two categories,
which are therefore subdivided. The binding mechanism largely influences the process speed and the resulting part properties.
Research limitations/implications – The classification presented is not claimed to be definitive. Moreover some SLM/SLM processes could be
classified into more than one category, based on personal interpretation.
Originality/value – This paper can be a useful aid in understanding existing SLS/SLM processes. It can also serve as an aid in developing new SLS/SLM
processes.

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Binding Mechanisms in Selective Laser Sintering and Selective Laser Melting

Binding mechanisms in selective laser sintering and selective laser melting

Selective laser sintering (SLS) is one of the most rapidly growing rapid prototyping techniques (RPT). This is mainly due to its suitability to process almost any material: polymers, metals, ceramics (including foundry sand) and many types of composites. The material should be supplied as powder that may occasionally contain a sacrificial polymer binder that has to be removed (debinded) afterwards. The interaction between the laser beam and the powder material used in SLS is one of the dominant phenomena that defines the feasibility and quality of any SLS process. This paper surveys the current state of SLS in terms of materials and lasers. It describes investigations carried out experimentally and by numerical simulation in order to get insight into laser‐material interaction and to control this interaction properly.

Ludo Froyen

Papers

Selective laser melting of iron-based powder

Binding Mechanisms in Selective Laser Sintering and Selective Laser Melting

Binding mechanisms in selective laser sintering and selective laser melting

Lasers and materials in selective laser sintering

Lasers and materials in selective laser sintering