A review on selective laser sintering/melting (SLS/SLM) of aluminium alloy powders: Processing, microstructure, and properties

This overview will focus on the direct fabrication of metal components by using laser-forming techniques in a layer-by-layer fashion. The main driving force of rapid prototyping (RP) or layer manufacturing techniques changed from fabrication of prototypes to rapid tooling (RT) and rapid manufacturing (RM). Nowadays, the direct fabrication of functional or structural end-use products made by layer manufacturing methods, i.e. RM, is the main trend. The present paper reports on the various research efforts deployed in the past decade or so towards the manufacture of metal components by different laser processing methods (e.g. selective laser sintering, selective laser melting and 3-D laser cladding) and different commercial machines (e.g. Sinterstation, EOSINT, TrumaForm, MCP, LUMEX 25, Lasform). The materials and applications suitable to RM of metal parts by these techniques are also discussed.

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Rapid Manufacturing of Metal Components by Laser Forming

As additive manufacturing (AM) process evolves from rapid prototyping to the end-of-use product manufacturing process, manufacturing constraints have largely been alleviated and design freedom has been significantly broadened, including shape complexity, material complexity, hierarchical complexity, and functional complexity. Inevitably, conventional Design Theory and Methodology (DTM) especially life-cycle objectives oriented ones are challenged. In this paper, firstly, the impact of AM on conventional DTM is analyzed in terms of design for manufacturing (DFM), design for assembly (DFA), and design for performance (DFP). Abundance of evidences indicate that conventional DTM is not qualified to embrace these new opportunities and consequently underline the need for a set of design principles for AM to achieve a better design. Secondly, design methods related with AM are reviewed and classified into three main groups, including design guidelines, modified DTM for AM, and design for additive manufacturing (DFAM). The principles and representative design methods in each category are studied comprehensively with respect to benefits and drawbacks. A new design method partially overcoming these drawbacks by integrating function integration and structure optimization to realize less part count and better performance is discussed. Design tools as a necessary part for supporting design are also studied. In the meantime, the review also identified the possible areas for future research.

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Additive manufacturing-enabled design theory and methodology: a critical review

Magnesium-based materials are used primarily in developing lightweight structures owing to their lower density. Further, being biocompatible they offer potential for use as bioresorbable materials for degradable bone replacement implants. The design and manufacture of complex shaped components made of magnesium with good quality are in high demand in the automotive, aerospace, and biomedical areas. Selective laser melting (SLM) is becoming a powerful additive manufacturing technology, enabling the manufacture of customized, complex metallic designs. This article reviews the recent progress in the SLM of magnesium based materials. Effects of SLM process parameters and powder properties on the processing and densification of the magnesium alloys are discussed in detail. The microstructure and metallurgical defects encountered in the SLM processed parts are described. Applications of SLM for potential biomedical applications in magnesium alloys are also addressed. Finally, the paper summarizes the findings from this review together with some proposed future challenges for advancing the knowledge in the SLM processing of magnesium alloy powders.

Selective Laser Melting of Magnesium and Magnesium Alloy Powders: A Review

The metal laser sintering (MLS) is used to make strong or hard metallic models for tools and dies directly from metallic powders. Thermal distortion is the serious problem after cooling of the solidified part rapidly. Uncontrolled temperature distribution in the metallic powder layer leads to thermal distortion of the solidified part. The study of temperature distribution within the metallic layer during MLS is important from the quality of the layer point of view. The high temperature generated in the powder layer leads to thermal distortion of the part and causes thermal as well as residual stresses in the part. In this paper the powder layer is assumed to be subjected to plane stress type of temperature variation and a transient finite element method-based thermal model has been developed to calculate the temperature distribution within a single metallic layer during MLS. A finite element code has been developed and validated with the known results from the literature. The obtained results of temperature distribution show the temperature and temperature gradient variation along X- and Y-axis. The effect of process parameters such as laser power, beam diameter, laser on-time, laser off-time and hatch spacing on temperature distribution within a model made of titanium during MLS is studied. The results computed by the present model agree with experimental results. Temperature increases with increase in laser power and laser on-time but temperature decreases with increase in laser off-time and hatch spacing.

Finite element analysis of temperature distribution in single metallic powder layer during metal laser sintering

A comparative characterisation of selective laser sintering (SLS) mechanisms of single‐ and two‐component powders is presented The effects of the volume fraction of liquid phase and the powder absorptance were discussed Single‐component Ni‐alloy, Fe and Cu powders as well as two‐component powder systems based on Ni‐alloy, Fe and Cu were investigated In particular, the following types of two‐component powder systems were studied: Ni‐alloy‐Cu and Fe‐Cu powder mixtures as well as Cu‐coated Ni‐alloy powder and Cu‐coated Fe powders SLS experiments were performed with a CW‐ Nd:YAG laser (λ=106 μm) The acting mechanism in all cases was liquid phase sintering

Sregei Mozzharov

Papers

Selective laser sintering of single‐ and two‐component metal powders