Viviane Lima Freitas da Silva

The influence of solution and aging heat-treatments on the corrosion behavior of a biodegradable Mg–Y–Gd–Zr alloy was investigated. Electrochemical behavior was assessed by potentiodynamic polarization curves and electrochemical impedance spectroscopy in an aerated 0.9 wt.% NaCl solution at 37 °C ± 0.1, complemented by SEM, EDS, and XRD analyses of corrosion-products. The as-cast condition exhibited the highest polarization resistance and impedance modulus, attributed to a thicker and more resistive corrosion-product layer, despite microstructural heterogeneity. Solution heat-treatment (525 °C/24 h) homogenized the microstructure and shifted the corrosion potential to nobler values, but produced a thinner, less protective film and reduced corrosion resistance. Among aged conditions, aging at 250 °C for 100 h yielded the best performance, with higher polarization resistance and impedance modulus values indicative of a more uniform and stable surface layer. Overall, the results demonstrate that corrosion behavior is primarily governed by the stability and resistive character of the corrosion-product layer, which is strongly controlled by the heat-treatment-induced microstructural state.

In order to develop a potential route to fabricate plates and clips for orthopedic applications, a Mg–3.4Dy–0.2Zn–0.4Zr (wt.%) alloy was produced and analyzed in different conditions: solution treated at 525 °C for 3 h, hot rolled and hot rolled and aged at 250 °C. The aging behavior of the rolled alloy was investigated during isothermal aging at 250 °C, and a significant peak was observed at 10 h. The electrochemical behavior was evaluated in 0.9 wt.% NaCl solution at 37 ± 0.5 °C by potentiodynamic polarization and electrochemical impedance spectroscopy. The 525 °C-3 h and hot rolled specimens exhibited corrosion rates of 2.0 and 1.7 mm/year, respectively. The hot rolled and aged at 250 °C for 10 h specimen presented a grain size of 11.8 ± 1.7 μm with an intense macrotexture of the basal {0002} plane, hardness of 73 ± 3 HV and higher impedance modulus and obtained the highest corrosion resistance with a corrosion rate of 0.9 mm/year.

The increasing global demand for iron ore pellets has made the pelletizing companies to step up their investments. The mechanical strength of the pellets, as well as its wear resistance are important factors to characterize the mechanical behavior. These properties are influenced by the type and nature of the ore or concentrate, the additives and the subsequent heat treatment used. This paper develops a numerical finite element model in order to characterize the mechanical behavior of iron ore pellets. The main objective of this study was to establish a valid finite element model that is able to simulate the mechanical behavior of iron ore pellets. The uniaxial compression test was made to evaluate the mechanical properties of the pellets. Furthermore, modeling and simulations are done using the software ABAQUS CAE® for uniaxial compression using the material properties obtained by the test. Lastly, in order to validate the model, the experimental data is crossed with the simulation results to discuss its correlation and particularities.