Additive manufacturing of metallic components – Process, structure and properties

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

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

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

Fundamentals of Selective Laser Melting of alloyed steel powders

The effective thermal diffusivity of metal powders in air at room temperature is measured by the photopyroelectric technique. The thermal conductivity is calculated from the diffusivity, the relative density, and the specific heat obtained from literature. Maxwell’s model is a good prediction but underestimates the measured effective thermal conductivity, especially for irregular particles. Due to the large difference between the thermal conductivity of metals and air, the effective conductivity is mainly determined by the relative density of the powder bed but not by the properties of the powder material. A theoretical model showing the influence of grain size and gas pressure is presented. The dependence on the particles’ size and pressure is explained by the gradual transition from the free molecular to conductive mechanism of heat transfer in gaps between particles. The theory gives a precise estimation of effective thermal conductivity for metallic powders with a narrow size distribution of spherical...

Marleen Rombouts

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

Fundamentals of Selective Laser Melting of alloyed steel powders

Photopyroelectric measurement of thermal conductivity of metallic powders