Mechanical Impact Toughness Research Articles

Characterizing Oxide Inclusions in Welded Lean Duplex Stainless Steels and Their Influence on Impact Toughness

In newly developed 2101 lean duplex stainless steel, oxide inclusions have been detected on welded metal zones after subjecting them to flux-cored arc welding with an E2209T1-1 flux-cored filler metal. These oxide inclusions directly affect mechanical properties of the welded metal. Hence, a correlation requiring validation has been proposed between oxide inclusions and mechanical impact toughness. Accordingly, this study employed scanning electron and high-resolution transmission electron microscopy to assess the correlation between oxide inclusions and mechanical impact toughness. Investigations revealed that the spherical oxide inclusions comprised a mixture of oxides in the ferrite matrix phase and were close to intragranular austenite. The oxide inclusions observed were titanium- and silicon-rich oxides with amorphous structures, MnO with a cubic structure, and TiO2 with an orthorhombic/tetragonal structure, derived from the deoxidation of the filler metal/consumable electrodes. We also observed that the type of oxide inclusions had no strong effect on absorbed energy and no crack initiation occurred near them.

New insight on improving electrical strength and toughness of polyethylene blends: Turning point of supramolecular structure

We report an effective approach on improving the electrical strength and mechanical impact toughness in polyethylene blends by locating the composition on a submicroscopic supramolecular structure turning point. The designed linear low density polyethylene (LLDPE)-high density polyethylene (HDPE) blends exhibit the enhanced electrical breakdown strength and toughness with the optimal value of E0=95.48kV/mm and G=54.67 kJ·m-2 respectively, which is around 6% and 18% higher than pure LLDPE. The scanning electron microscopic (SEM) investigation and X-ray diffraction (XRD) study show no obvious variation in mesoscopic and microscopic structure with the change of HDPE content. Further differential scanning calorimetric (DSC) study using successive self-nucleation/annealing (SSA) method reveals that the turning point with optimal performance corresponds with a peculiar supramolecular structure with a high density of tie molecules, which enhances the toughness and the electromechanical breakdown strength. Our work provides a new insight on improving electrical strength and toughness for dielectric polymers, and may aid to enhance the electric insulation performance for dielectric materials in power equipment.