(i) Objective: The present study aimed to compare the electrochemical corrosion resistance of six different types of fixed lingual retainer wires used as fixed retention appliances in an in vitro study. (ii) Methods: In the study, two different Ringer solutions, with pH 7 and pH 3.5, were used. Six groups were formed with five retainer wires in each group. In addition, 3-braided stainless steel, 6-braided stainless steel, Titanium Grade 1, Titanium Grade 5, Gold, and Dead Soft retainer wires were used. The corrosion current density (i_corr), corrosion rate (CR), and polarization resistance (R_p) were determined from the Tafel polarization curves. (iii) Results: The corrosion current density of the Gold retainer group was statistically higher than the other retainer groups in both solutions (p < 0.05). The corrosion rate of the Dead Soft retainer group was statistically higher than the other retainer groups in both solutions (p < 0.05). The polarization resistance of the Titanium Grade 5 retainer group was statistically higher than the other retainer groups in both solutions (p < 0.05). As a result of Scanning Electron Microscope (SEM) images, pitting corrosion was not observed in the Titanium Grade 1, Titanium Grade 5 and Gold retainer groups, while pitting corrosion was observed in the other groups. (iv) Conclusion: From a corrosion perspective, although the study needs to be evaluated in vivo, the Titanium Grade 5 retainer group included is in this in vitro study may be more suitable for clinical use due to its high electrochemical corrosion resistance and the lack of pitting corrosion observed in the SEM images.

With the discovery of high entropy alloys, new materials with superior properties have emerged. According to recent research, high-entropy alloys’ multi-component structure and mixing entropy have made them more prominent than other alloys. Because of their excellent chemical and mechanical properties—such as high hardness, high-temperature resistance, high wear resistance, chemical stability, and high corrosion resistance—high entropy alloys outperform other material types in various applications. A new grade of mechanically alloyed high entropy alloy (HEA) of composition 23Fe-21Cr-18Ni-20Ti-18Mn was consolidated by a hot isostatic pressing (HIP) at a temperature of 1000 °C, at different sintering time of 30, 60, and 90 min respectively. We have investigated the impact of sintering time on the microstructure, mechanical, corrosion, and wear-resistance properties. The x-ray diffraction (XRD) spectra of the 30 min HIPed HEA sample showed dominant s-FeCr phases and traces of γ-Fe, and the Ni-Ti phases. Whereas, the 90 min HIPed HEA samples showed more dominant Ni-Ti and traces of γ-Fe, and β-Mn phases. There is a phase transformation from BCC to HCP of consolidated HEA at increased holding time. The density of the samples increases from 5.882 to 6.327 g cm⁻³ and the porosity percentage decreases from 12.93 to 6.35% with the increase in the holding time. The Vickers microhardness value for 30, 60, and 90 min HIPed 23Fe-21Cr-18Ni-20Ti-18Mn HEA at 1000 °C was found to be 433, 513, and 793 HV respectively at an indentation load of 0.1 kgf. The consolidated HEA sample undergoes an abrasive and oxidative wear mechanism with ploughing and plastic deformation modes. The morphology of the wear debris was investigated using SEM. The 90 min sintered sample showed an excellent corrosion resistance due to the high rate of material densification and minimum surface flaws.

Dense nanostructured carbides existing in ternary system Ti-Cr-C were elaborated thanks to a two-steps method. In the first step, nanostructured Ti_0.9Cr_0.1C carbides were prepared by high-energy planetary ball milling under various times (5, 10, and 20 h), starting from an elemental powder mixture of titanium, chromium, and graphite. In the second step, these nanostructured powders were used to produce densified carbides thanks to the spark plasma sintering (SPS) process under a pressure of 80 MPa. The temperature was fixed at 1800 °C and the holding time was fixed at 5 min. Microstructural characteristics of the samples were investigated using X-ray diffraction (XRD). Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX) was used to investigate the morphology and elemental composition of the samples obtained using SPS. The novelty of this work is to understand the effect of SPS on the microstructural and electrochemical properties of the nanostructured Ti_0.9Cr_0.1C carbides. The XRD results showed that, during sintering process, the (Ti,Cr)C carbide was decomposed into TiC, Cr₇C₃, and Cr₃C₂ phases. An amount of iron was detected as contamination during milling, especially in the case of a sample obtained from 20 h milled carbide. The bulk obtained from the milled powders for 5 and 20 h present similar relative densities of 98.43 and 98.51%, respectively. However, the 5 h milled sample shows slightly higher hardness (93.3 HRA compared to 91.5 HRA) because of the more homogeneous distribution of the (Ti,Cr)C phases and the low iron amount. According to the 0.0011 mm/year corrosion rate and 371.68 kΩ.cm² charge transfer resistance obtained from the potentiodynamic polarization and EIS tests, the 20 h carbide was the specimen with the highest corrosion resistance.

This study investigates the impact of zinc (Zn) content on the microstructure and mechanical properties of (70‐ x )Fe‐30Mn‐ x Zn ( x = 0, 3, 6, and 9 wt%) nanocrystalline alloys produced using mechanical alloying and subsequently formed into pellets through hot pressing and sintering. X‐ray diffraction analysis indicates that Fe‐30Mn‐ x Zn ( x = 0, 3, 6, and 9 wt%) particles exist in the austenite phase. According to scanning electron microscopy/energy‐dispersive X‐ray spectroscopy results, elemental distribution is homogeneous. Density tests of consolidated samples are performed by the Archimedes method. Among the tested alloys, the Fe‐30Mn‐9Zn alloy shows the highest relative density at 94.21%. Additional tests are performed to evaluate hardness, wear resistance, bending strength, corrosion behavior, and antibacterial properties. The Fe‐30Mn alloy has the highest hardness and wear resistance with a 548.66 HV value, which can be attributed to the solid solution hardening mechanism. The Fe‐30Mn‐9Zn alloy displays a bending strength of 1277.61 MPa and the lowest corrosion rate of 0.044 mm year ⁻¹ with potentiodynamic polarization tests, attributed to low porosity. Antibacterial tests conducted using the colony counting method with Staphylococcus aureus and Escherichia coli bacteria show that increasing the zinc content significantly enhances the antibacterial properties of the alloy.

Novel pure Zn and Zn-3Ag-xFe (x = 0, 1, 3, 5) (wt.%) nanocrystalline powders were synthesized for potential use as implants and stent materials by the mechanical alloying (MA) technique. The morphological and structural alterations of the powders milled for 5, 10, and 20 h were examined. SEM research revealed that during MA, the original elemental powder particles were subjected to a cold-welding process, subsequently fracturing in a brittle manner. The EDX spectra of the powders milled for 20 h indicated a uniform distribution of components. Laser diffraction particle size examination proved that the Zn-3Ag-1Fe alloy had the smallest particle size at 58.8 µm. XRD examination indicates the existence of AgZn₃ and Fe₃Zn₁₀ intermetallic phases. The crystallite size diminishes with prolonged milling time, decreasing from 130 nm to 30 nm. The porosity rose from 11.62% for pure Zn to 15.35% in the Zn-3Ag-5Fe alloy, suggesting that the incorporation of Ag and the higher Fe ratio diminished the compressibility of the milled powders, as evidenced by density tests. The Zn-3Ag-5Fe alloy exhibited the maximum corrosion current density of 164.65 µA/cm², attributed to the microgalvanic effect and reduced relative density induced by the Fe₃Zn₁₀ phase, which escalated with higher Fe doping. The hardness of the Zn-3Ag-5Fe alloy rose from 34.5 ± 2.8 HV to 132.2 ± 4.6 HV compared to the pure Zn sample, while the wear coefficient decreased from 0.029 ± 0.003 mm³/Nm to 0.005 ± 0.001 mm³/Nm, corresponding with the hardness test results. In contrast to S. aureus, which exhibited an 87.8% susceptibility to antibacterial activity from 3% silver and iron additions, E. coli demonstrated over 85% susceptibility to antibacterial activity from silver addition alone. The Zn-3Ag and Zn-3Ag-1Fe samples demonstrated high biocompatibility, attaining cell survival rates of 99.2% ± 3.01% and 99.2% ± 4.02% for the 12.5% extract, respectively. This study demonstrates that the newly developed Zn-Ag-xFe alloys have exceptional mechanical properties and excellent biocompatibility. Furthermore, the variable biodegradation rate dependent on alloy type presents an avenue for further research.

In order to produce nanostructured Ti0.9Cr0.1C powders, an elemental powder mixture of titanium, chromium, and graphite is milled in this work using a high-energy ball mill for various milling times. Microstructural characteristics such as crystallite size, microstrain, lattice parameter, and dislocation density are determined using X-ray diffraction (XRD). Mechanical alloying successfully produced nanocrystalline (Ti,Cr)C with an average crystallite size of 11 nm. This size of the crystallites is also directly verified using transmission electron microscopy (TEM). Scanning electron microscopy (SEM) was used to investigate the morphology of the samples. The novelty of this work is advancing the scientific understanding of the effect of milling time on the particle size distribution and crystalline structure, and also understanding the effect of the spark plasma sintering on the different properties of the bulks. Densified cermet samples were produced from the nanocrystalline powders, milled for 5, 10 and 20 hours by SPS process at 1800 degrees for 5 min under a pressure of 80 MPa. Phase changes of the produced cermets were examined according to XRD, SEM/EDX analyses. Significant amounts of Cr and Fe elements were detected, especially in the 20 h milled cermet. The bulk forms of the milled powders for 5 and 20 h had a relative density of 98.43 and 98.51 %, respectively. However, 5 h milled cermet had 93.3 HRA because of the more homogeneous distribution of the (Ti,Cr)C phase, the low iron content and high relative density. According to the 0.0011 mm/year corrosion rate, and 371.68 kΩ*cm2 charge transfer resistance obtained from the potentiodynamic polarization and EIS tests, the 20 h cermet was the specimen with the highest corrosion resistance.