Biomedical nanocrystalline metals and alloys: structure, properties and applications

Effect of Processing Parameters on Strength and Corrosion Resistance of Friction Stir-Welded AA6082

The friction stir welding method is increasingly attracting interest in the railway sector due to its environmental friendliness, low cost, and ease of producing high-quality joints. Using aluminum alloys reduces the weight of structures, increasing their payload and reducing fuel consumption and running costs. The following paper presents studies on the microstructure, strength, and corrosion resistance of AA6082 aluminum alloy sheets joined via friction stir welding. The sheets were joined by employing two different traverse speeds (200 and 250 mm/min), two different rotational speeds (1000 and 1250 rpm), and two different tool tilt angles (0° and 2°). It was observed that the use of the inclined tool provides finer microstructure in the nugget zone, higher value of microhardness, and better corrosion resistance, compared to the tilt angle equal to 0°. By increasing the value of revolutionary pitch, finer grains are observed in the nugget zone and the measured hardness is higher. It was also observed that the change in process parameters strongly influences the radius of the nugget zone and the potentiodynamic properties of the friction stir-welded material. The joints produced with the tool tilt angle equal to 2°, the tool traverse speed of 200 mm/min, and its rotational speed of 1250 rpm revealed the highest hardness in the nugget zone (about 92% of the base material). Moreover, the finest grain size in the nugget with the average value of 9.8 ± 1.5 µm was found. The lowest corrosion current density equal to 16.029 µA cm−2 was noted for the sample with the highest strength, which also provides its good corrosion resistance.

In vitro comparison of physical, chemical, and mechanical properties of graphene nanoplatelet added Angelus mineral trioxide aggregate to pure Angelus mineral trioxide aggregate and calcium hydroxide

It is important to cover the pulp surface with a biocompatible material that is physically, mechanically, and chemically adequate. Graphene has the potential to form hard tissue, but at high doses, it shows toxic effects. It can be added to biocompatible materials at low doses to enhance their hard tissue forming potential. The aim of this study was to compare the physical, chemical, and mechanical properties of graphene nanoplatelet (GNP) added Angelus mineral trioxide aggregate (A-MTA) to pure A-MTA and calcium hydroxide. Homogeneous mixtures (created by adding +0.1 weight[wt]% and 0.3 wt% GNP to A-MTA), pure A-MTA, and Dycal were used. Three disc-shaped samples of each material were prepared using Teflon mold. Scanning electron microscope-energy dispersive X-ray (SEM-EDX), particle size, microhardness, and Fourier transform infrared spectroscopy (FTIR) analysis of the materials were performed in vitro. Data were analyzed using Kruskal-Wallis test followed by Conover test (p < .001). A-MTA and GNP added samples showed similar peaks in FTIR analysis. In the EDX analysis, the amount of carbon was observed with a higher increase at A-MTA + 0.3 wt% GNP than A-MTA + 0.1 wt% GNP. In the SEM image, hollow structure and particle size decreased as the amount of GNP increased; particle size was smaller at A-MTA + 0.3 wt% GNP than A-MTA + 0.1 wt% GNP (p < .001). A-MTA + 0.3 wt% GNP showed the highest microhardness while Dycal showed the lowest microhardness. The addition of GNP, a material with high potential for forming hard tissue, to the structure of capping materials can also positively contribute to the microhardness of the capping materials.