Enhanced Strength and Hardness of AS41 Magnesium Alloy Fabricated by Selective Laser Melting

AS41 magnesium alloy possesses outstanding performance features such as light weight, high strength to toughness ratio and excellent heat resistance due to the addition of Si element, while traditional casting methods are prone to inducing large grain size and coarse Mg2Si phase. In this study, we first reported utilizing the selective laser melting (SLM) technique, fabricating AS41 samples and exploring the effect of laser energy densities on the metallurgical quality by characterizing and investigating the microstructure and mechanical properties. Results showed that the optimal laser energy density range was 60 to 100 J/mm(3). Average grain size of only 2.9 mu m was obtained with weak texture strength of 1.65 in {0001} orientation. Meanwhile, many dispersed secondary beta-Mg17Al12 and Mg2Si phases were distributed inside the alpha-Mg matrix. It was confirmed that the SLM process introduced more grain recrystallization, inducing giant high-angle grain boundaries (HAGBs) and hindering the movement of dislocations, therefore forming dislocation strengthening while achieving grain refinement strengthening. Finally, three times the ultimate tensile strength of 313.7 MPa and higher microhardness of 96.4 HV than those of the as-cast state were obtained, verifying that the combined effect of grain refinement, solid solution strengthening and precipitation strengthening was responsible for the increased strength. This work provides new insight and a new approach to preparing AS41 magnesium alloy.

Automated summary

This study successfully fabricated AS41 magnesium alloy samples using selective laser melting (SLM) technique, and investigated the effect of laser energy densities on the metallurgical quality. Results showed that the optimal laser energy density range was 60 to 100 J/mm³. The SLM process introduced more grain recrystallization and hindered the movement of dislocations, resulting in dislocation strengthening and grain refinement strengthening. The ultimate tensile strength and microhardness were significantly improved compared to the as-cast state.