Magnesium Alloy 3D Printing by Wire and Arc Additive Manufacturing (WAAM)
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.553
Magnesium Alloy 3D Printing by Wire and Arc Additive Manufacturing (WAAM) David A. Martinez Holguin1, Seungkyu Han and Namsoo P. Kim1,* 1 Metallurgical, Materials and Biomedical Engineering Department, The University of Texas at El Paso, TX, USA
*Corresponding author. Tel: +1 915-747-7996; fax: +1 915-747-8036; e-mail: [email protected]
ABSTRACT
Mechanical properties similar to natural bone and good biocompatibility make magnesium a great option for its use as biodegradable implant material. The use of castings as fabrication technique brings inherent problems, such as segregation and void formation. Also, the architecture of the specimens created by using these techniques is limited. This study shows the implementation of WAAM for the fabrication of elements made out of AZ91D magnesium alloy (9% aluminium and 1% zinc). The results demonstrate that porosity or cracking only appears at the surface of the individual printed lines, while the central sections presents a voidless structure composed by an HCP magnesium matrix and a high density of well dispersed aluminium-zinc rich precipitates. EDS mapping confirms the presence of orthorhombic Al5Mg11Zn4 phase. Also, the relationship between the heat present in the system and the morphology of the lines is analysed.
INTRODUCTION Despite recent increases in the use of ceramics, polymers, and polymer matrix composites for bone healing applications [1], metallic components continue to be the most widely used option for this purpose [2]. Stainless steel, titanium, and cobalt-based alloys are the most commonly used metals to heal or replace damaged bones. Superior mechanical properties in contrast to those of ceramics and polymers make metallic biomaterials suitable for their use inside the human body. However, the elastic moduli of the metal implants are significantly larger than that of the natural bone, causing stress shielding. Further limitations arise from the possible liberation of harmful metallic ions inside the organism due to corrosion mechanisms, as well as debris formation due to wear,
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that lead to inflammation in the areas near the biomedical device [3]. One of the cause of inefficiency with conventional metal powders on 3d printing is due to initial 60~70 vol. % of particle-packing-factor leading to ineffective heat transfer [4]. By increasing the packing density with nano metal particles can effectively fix the heat transfer problem [5],[6]. Magnesium has been studied as an alternative for bone healing purposes due to its mechanical properties and degradability inside the human body. Being lighter than Aluminium (1.74 g/cm3 compared to 2.7 g/cm3), Magnesium presents fracture toughness greater than ceramic biomaterials. Upon decomposition, Magnesium ions (es
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