Kulekci, 2008 : Magnesium and its alloys applications in automotive industry (https://doi.org/10.1007/s00170-007-1279-2)
As shown in the graph, Mg has a comparable specific stiffness with aluminum and iron but a significantly higher specific strength. This property makes Mg and its alloys perfect candidates for lightweight applications in various industries such as the automotive and aerospace industries.
Some applications of Mg alloys in the automotive industry (Automotive Uses of Magnesium Alloys: Part One : Total Materia Article)
Another important application of Mg alloys is in the field of medical science where biocompatible implants made of Mg alloys are widely used for bone regeneration. Classical implants are usually made of Titanium alloys but those alloys are not biodegradable and thus necessitates a second operation to remove implants after bone regeneration. Moreover, the density and elastic modulus of Mg alloys are close to that of human bones. According to Li and al. (2021), this allows reducing local inflammatory response of the body observed with Ti alloys based implants.
The poor properties of pure Mg makes it mandatory to add alloying elements such as Al or rare earths (RE) elements. Many classes of Mg alloys were studied in the past decades and tailored alloys have been developed with specific properties for each applications.
Some of those alloys presents wider applications such as Mg-Al and Mg-RE based alloys. In the first class, aluminium provides solution strengthening by precipitating intermetallic compounds. However, few scientific publications are available for the laser powder based fusion (LPBF) of Mg-Al alloys. This alloys in mainly used for industry applications and forbidden in the medical sector because of the presence of Al, known to produce Al3+, a neurotoxic ion that can lead to Alzheimer’s disease.
Biocompatible alloys containing no toxic elements such as Mg-RE class WE43 alloy are also studied. Increasing interests grew for the LPBF production of this alloy because of the wide range of applications. The chemical composition of WE43 powder used for LPBF is in the following table.
In this section, a brief state of the art of the mechanical and electrochemical properties of Mg alloys obtained by LPBF is given.
Mechanical properties of Mg alloys are sufficient for most applications but ductility is lower than cast Mg. The table below gives some mechanical properties of WE43 :
mechanical properties of WE43
For most alloys presented in the review of Zeng and al. (Recent progress and perspectives in additive manufacturing of magnesium alloys, (2022)), elongation at break is below 5%, which makes them inoperable in the as-built state for most industrial applications. For some alloys such as WE43, a heat treatment is sufficient to achieve interesting elongation at break.
Researchers have been studying electrochemical durability of WE43 to evaluate the dissolving of an implant in the human body. The implant needs to maintain its mechanical stability for the first month and then gradually decade until fully dissolving after three months.
Results from Zeng and al. (2022) shows that WE43 is a promising candidate because of its fast decaying in body fluids, and thanks to its density and elastic modulus close to human bones (around 45 GPa).
Industry interests for additive manufacturing technology have grown exponentially over the past decade, especially for LPBF technology, which offers highest quality standards. Transport industries are paving the way: reducing weight by creating lighter structures increases fuel efficiency.
Topology optimization allows reducing the weight of a structural component by placing material only where it needs to be, following the stress gradients. However, topology optimization creates complex forms and curves, which are difficult to build using traditional processes. AM solved this problem.
The most famous example of use of AM in the automotive industry for a series production is the development by Bugatti and SLM Solutions of a brake caliper made of titanium. It is the largest mass-produced 3D printed part made of Ti.
Bugatti and SLM Solutions 3D printed brake caliper made of Ti : WATCH: Bugatti prepares 3D printed brake caliper for series production – 3D Printing Industry
Additive manufacturing of Mg alloy for industrial use is still in its early phase but could offer interesting opportunity to increase weight reduction. WE43 could be a good candidate to replace Ti or Al for lightly stressed components at room temperature and up to 300°C.
Architected materials are multiphase and/or cellular materials in which the topological distribution of phases is controlled and optimized to reach specific properties (Introduction | Journal of Materials Research | Cambridge Core, L. Valdevit, Cambridge University Press, 2018). Lattice structure are architected materials with a stochastic phase like foams for example or periodic phase such as a regular body centered cubic (BCC) network.
BCC WE43 lattice structure obtained by LPBF by Li et al. (2021) : https://doi.org/10.1016/j.msec.2020.111623
Li and al. studied the influence of the lattice density, microstructure and surface treatment on the mechanical properties, corrosion resistance and cytocompatibility of WE43 obtained by LPBF.
Creating such structures have multiple advantages such as increasing the specific surface to increase chemical reactivity. It also allows creating lightweight structure with high specific strength. For a BCC structure, strut dimeters drives density levels of the structure as shown in the image above.
Titanium cranial implants obtained by LPBF are already used to help patients with special needs such as the one presented in the image below:
Titanium cranial implant obtained by LPBF (Cranial implant created by additive manufacturing | Scientist Live)
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Magnesium (Mg) alloys are widely used in multiple light-weighing applications in industries such as automotive, aerospace or medical science. Its low density and biocompatibility makes it a perfect match for bone implants for example. Commercial additive manufacturing (AM) of Mg alloy WE43 is now available with the latest development of Aconity3D, discover some applications of AM-Mg in this article!