Directed energy deposition of metals: processing, microstructures, and mechanical properties

Abstract

Amongst the many additive manufacturing (AM) techniques, directed energy deposition (DED) is a prominent one, which can also be used for the repair of damaged components. In this paper, we provide an overview on it, with emphasis on the typical microstructures of DED alloys and discuss the processing-microstructure-mechanical property correlations. Comparison is made with those manufactured using the conventional techniques and those obtained with laser beam powder bed fusion (LB-PBF). The characteristic solidification rates and thermal histories in DED result in distinct micro-and meso-structural features and mechanical performance, which are succinctly summarized. The potential of DED for manufacturing graded materials and for component repair is elaborated while highlighting the key-associated challenges and possible solutions. Modelling and simulation studies that facilitate an in-depth understanding of the DED technique are summarized. Finally, some critical issues and research directions that would help develop DED further and extend its application potential are identified.

Recent innovations in laser additive manufacturing of titanium alloys

“…The commonly adopted parameters range used in LPBF and LDED are listed in figure 3. The effects of these process variables on the fabricated part's relative density have been wellreviewed and discussed previously [13][14][15][27][28][29]. For the Ti alloys, the microstructure and properties can be well-tailored through variations of the processing parameters.…”

“…With the significant developments of AM over the past decade, several reviews on AM of Ti alloys have been published [6,[13][14][15][16][17][18][19][20]. For instance, Nguyen et al [21] systematically reviewed the microstructure and properties of additively manufactured Ti-6Al-4V alloy.…”

“…The LDED process is more suitable for fabricating large-format components and multi-materials due to the high processing flexibility and high productivity. Hence, the LDED Ti alloy parts are mainly employed in aerospace, automotive, marine and offshore fields [15]. Nevertheless, the LPBF and LDED techniques share many similar process parameters, including laser power, scan speed, hatch space, etc.…”

A review of various materials for additive manufacturing: Recent trends and processing issues

“…In addition, DED techniques have some common drawbacks also that mainly include requirement of support structure, comparatively low surface finish, etc. [139,140].…”

Optimising the manufacturing of a β-Ti alloy produced via direct energy deposition using small dataset machine learning

“…These three parameters were chosen as variable process parameters for this study. GED was chosen as nomenclature, as referenced by Wolff et al 6 becoming common in recent reviews 7 , 8 but can also be referenced as effective energy density 1 , laser energy density (LED) 5 and laser energy area density (EAD) 4 . Furthermore, it is worth noting that these process parameters do not encapsulate the full gamut of available variable processing parameters.…”