Metals

To explore the improvement of the corrosion resistance of the inner bottom plate of corrosion-resistant storage tank steel and the effects and underlying mechanisms of varying molybdenum (Mo) contents (0Mo, 0.15 wt.%Mo, 0.30 wt.%Mo, and 0.60 wt.%Mo), a systematic study is conducted on the corrosion performance of the steel in a simulated environment (10 wt.% NaCl solution, 30 ± 1 °C). The findings reveal that the steel containing 0.3 wt.% Mo possesses superior corrosion resistance. An optimal dosage of Mo refines corrosion products and fills voids via the formation of nano-scale MoO₂/MoO₃ particles, mediates the evolution of γ-FeOOH towards α-FeOOH, and improves the protective capability and electrochemical stability of the rust layer. Nevertheless, excessive Mo leads to the residual of elemental Mo arising from incomplete oxidation, which constructs a galvanic cell with Fe, thereby accelerating corrosion. Additionally, an excessively high proportion of MoO₃ triggers elevated internal stress and structural degradation of the rust layer.

FEM numerical analyses can be indicated as a common and basic tool used in the design of processes based on the plastic forming of metals. In such simulations, the accuracy of the results strongly depends on the quality of the material constitutive data used as the input. Good understanding of metals and their alloys’ deformation behavior, especially at hot working temperatures, is the key to developing or optimizing proper and economical processes. To provide reliable FEM simulation results, it is crucial to select an appropriate experimental method describing material behavior at elevated deformation temperatures. The most commonly method used for this is hot torsion tests, which can effectively provide a basis for developing constitutive models (for example, the Hensel–Spittel equation), but also produce the material constants needed to fully describe the behavior of the metal. This paper analyzes three experimental methods, compression testing, torsion testing, and spherical probe pressing, for determining material flow stress characteristics required for FEM simulations. The study focuses on the EN AW-7075 alloy, a high-strength aluminum alloy with limited hot workability. The methods were validated by comparing FEM predictions of extrusion force and profile temperature with results from industrial extrusion trials conducted on a 5 MN horizontal press.

Magnesium alloys’ poor corrosion resistance limits their applications as biodegradable bone repair materials. Alloying tailors Mg alloys’ microstructure and properties. The present study investigates the effect of 2 wt.% Ag addition on the microstructure and initial corrosion behavior of hot-rolled Mg-1Ca alloy. Mg-1Ca and Mg-1Ca-2Ag alloys were prepared by melting using Mg-2Ca and Mg-4Ag master alloys, followed by homogenization at 400 °C for 2 h, hot rolling, and stress-relief annealing at 400 °C for 6 h. The alloys were systematically characterized using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), and X-ray diffraction (XRD). Initial corrosion behavior was evaluated via 3 h immersion tests in simulated body fluid (SBF). Results reveal Ag’s high thermal diffusivity promotes segregation at tensile twin boundaries, forming Ag₃Mg nanoparticles. These nanoparticles hinder grain boundary migration and, with increased deformation, facilitate grain rotation and high-angle grain boundary formation, weakening texture. Internal stress accumulation near twin boundaries—driven by grain orientation variation and nanoparticles—induces ~86° rotation of {10–12} tensile twins around the c-axis, forming double twins. During corrosion, nanoparticles and double twins synergistically promote dense protective film formation, significantly reducing corrosion rates.