Magnesium and its alloys have increasingly gained attention among practitioners and engineers due to their attractive properties, specifically their high specific strength that renders these materials suitable for several applications in different industries. However, their use is still limited, especially in load-bearing applications, due to the limited knowledge of their fracture behavior, especially in the presence of notches. The aim of this work is thus that to fill this lack, investigating the fracture behavior of notched ZK60-T5 magnesium. Eleven different notch geometries were considered, i.e. U notched specimens with notch radii of 1.5, 3, 4, 5, and 6 mm and V notched specimens with notch opening angles of 35°, 60° and 90°, and notch radii of 0.4 and 0.8 mm. The mechanical tests showed that the presence of notches reduces the ductility of the material. This was confirmed also by the fracture surface analyses carried out by means of Field Emission Scanning Electron Microscope (FE-SEM), where the size of the shear lips was shown to decrease by increasing the notch acuity. In addition, this work aims also to provide practitioners and engineers with a tool able to predict the failure loads irrespective of the notch geometry. For the first time on Mg samples, a local approach, i.e. the Strain Energy Density (SED), is used to predict the failure loads of the differently notched samples, and the results suggest high reliability of this approach, being the deviations between the experimental and the theoretical data often lower than 10%.
The present investigation is concerned with high-cycle axial fatigue testing of a 2 mm AA6060-T6 HYB butt weld produced in the solid state using AA6082 filler metal addition. The results complement the three-point bend testing and the tensile testing done in two previous studies. In this study, optical microscope and scanning electron microscope examinations have been carried out to reveal the joint macro/microstructure and document possible surface and root defects deemed to affect fatigue life. In the as-welded condition, the HYB weld suffers from surface irregularities at the weld face and “kissing” bond formation in the root region. Despite of this, the subsequent testing shows that the fatigue properties exceed those reported for comparable AA6082-T6 gas metal arc butt welds and matching those reported for corresponding high-strength laser beam and friction stir weldments.
The fatigue behaviour of notched and unnotched specimens produced by additively manufactured Inconel 718 are analysed in the as-built and heat-treated conditions. The surfaces display high roughness and defects acting as fatigue initiation sites. In the as-built condition, fine sub-grains were found, while in the heat-treated state, the sub-grains were removed and the dislocation density recovered. SN-curves are predicted based on tensile properties, hardness and defects obtained by fractography, using the √area-method.
The present investigation is concerned with high-cycle axial fatigue testing of a 2 mm AA6060-T6 HYB butt weld produced in the solid state using AA6082 filler metal additions. It complements the three-point bend testing and the tensile testing done in two previous studies. Also, optical and scanning electron microscope investigations have been carried out to reveal the macro/microstructure and document possible surface & root defects deemed to be destructive to fatigue life. In the as-welded condition, the HYB weld suffers from surface irregularities at the weld face and “kissing” bond formation in the root region. Still, these defects are not devastating for the structural integrity. As a matter of fact, the subsequent benchmark testing shows that the fatigue properties surpass those reported for a comparable AA6082-T6 gas metal arc butt weld and fully match those reported for corresponding high-strength laser beam and friction stir weldments.