Additive manufactured WE43 magnesium: A comparative study of the microstructure and mechanical properties with those of powder extruded and as-cast WE43

Abstract

Laser powder-bed fusion (L-PBF), an additive manufacturing (AM) method, was employed to produce WE43 magnesium cubes with minimal porosity. These samples were subjected to microstructural analysis by utilizing optical light and scanning electron microscopy techniques in addition to x-ray diffraction and compared to powder extruded and as-cast WE43 reference samples. The mechanical properties of the three materials were evaluated via tensile testing. Furthermore, the microstructure of the original powder material was investigated. The additive manufactured samples and the powder extruded (PE) samples showed an extremely fine, homogeneous microstructure with grain sizes of ~1 μm and very fine secondary phases; the crystallographic structure of these phases could not be indisputably identified via XRD except for yttrium oxides. The microstructure of the as-cast material revealed different phases. Laser scan traces can clearly be observed in the microstructure as a result of the applied exposure strategy or small clusters of orientated grains that may be correlated to differing heat impacts between the center and edge-near areas of the sample due to melt pool preservation during the direction change of the laser path.Tensile tests show a significant alteration of properties in comparison to the tested conventional as-cast material. The tensile tests of the additive manufactured and powder extruded material revealed an ultimate tensile strength of 308 and 306 MPa at 12 and 22% elongation to failure, respectively. For both materials, an upper and lower yield point phenomenon was observed which is attributed to the fine grain size. The presented investigations render the additive manufacturing (AM) process suitable to produce samples that show a homogeneous and dense microstructure, mostly independent of the build direction, with exceptional high mechanical properties and to exhibit to a great extend similar features to powder extruded samples.