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The effect of hydrogen content on the deformation and fracture behavior of 27Cr−4Mo−2Ni super ferritic stainless steel (SFSS) was investigated in this study. It was shown that the plasticity and yield strength of SFSS were very susceptible to hydrogen content. The introduction of hydrogen led to a significant decrease in elongation and a concurrent increase in yield strength. Nevertheless, a critical threshold was identified in the elongation reduction, after which the elongation remained approximately constant even with more hydrogen introduced, while the yield strength exhibited a monotonic increase with increasing hydrogen content within the experimental range, attributed to the pinning effect of the hydrogen Cottrell atmosphere on dislocations. Furthermore, the hydrogen-charged SFSS shows an apparent drop in flow stress after upper yielding and a reduced work hardening rate during the subsequent plastic deformation. The more hydrogen is charged, the more the flow stress drops, and the lower the work hardening rate becomes. [ABSTRACT FROM AUTHOR]

This study systematically evaluated the impact of dual-phase zone annealing on the microstructure and mechanical properties of cold-rolled 430 Ferritic Stainless Steel (FSS), focusing on the phase transformation process from ferrite to austenite and the dissolution and precipitation behavior of the M 23 C 6 phase. The annealing process significantly affects the microstructural characteristics of ferrite and martensite, including grain size, the distribution of grains of various sizes, aspect ratio, and phase content. The amount of martensite first increased and then decreased with rising annealing temperatures. The sample annealed at 1050 °C exhibited the highest martensite content of 29.5%. The variation in martensite content reflects the complex interplay between phase transformation kinetics and thermodynamic equilibrium. As the annealing time increased or temperature rose, the M 23 C 6 phase at ferrite grain boundaries gradually dissolved and re-precipitated at higher temperatures. At lower temperatures, the M 23 C 6 phase precipitated within martensite, but as the temperature increased, the precipitated phase diminished until it disappeared. Temperature changes affect the solubility of precipitates, atomic diffusion rates, and the uniform distribution of atoms across different phases. Appropriately increasing annealing temperature or extending annealing duration enhances the strength and hardness of 430 FSS. However, excessively high annealing temperatures lead to a decline in mechanical properties. The sample annealed at 1000 °C demonstrated the best mechanical properties, achieving a tensile strength of 783 MPa and an elongation of 16.0%. Furthermore, the analysis of fracture morphology and yield behavior in stress-strain curves further elucidated the macroscopic mechanical performance of the material. • Controlling dual-phase zone annealing parameters is crucial for enhancing the mechanical properties of 430 FSS. • The variation in martensite content with temperature exhibits non-monotonic behavior. • Temperature changes affect the dissolution and precipitation behavior of the M 23 C 6 phase. • Pure ferritic specimens and dual-phase structured specimens exhibit different yielding behaviors. [ABSTRACT FROM AUTHOR]

[Display omitted] • The increased Y addition transforms solute-rich SFs into 18R-LPSO and 14H-LPSO structures. • Good combination of the strength and ductility is obtained in the present as-cast alloys. • LPSO structures suppresses the interior corrosion of the α-Mg matrix. The microstructures, mechanical properties, and corrosion behaviors of Mg-4Gd- x Y-1Zn-0.5Ca-1Zr (x = 1, 3, and 5 wt.%) alloys under as-cast condition were studied. The results indicate that all the alloys are composed of α-Mg matrix, eutectic phase, and lamellar stacking faults (SFs) located at the outer edge of the α-Mg grains. The plate-like long period stacking ordered (LPSO) structures are found in the alloys with higher Y content. The nano hardness of different phases obeys the following order: eutectic phase > SFs/LPSO structure > α-Mg matrix. Higher Y concentration leads to the nano hardness enhancement of the α-Mg matrix and more uniform hardness distribution. Tensile tests at ambient temperature indicate that Y addition plays a crucial role in improving the yield strength of the as-cast alloys. The corrosion properties of the as-cast alloys after immersion in 3.5 wt.% NaCl solution for 60 h reveal that Mg-4Gd-3Y-1Zn-0.5Ca-1Zr alloy shows a more uniform corrosion morphology and better corrosion resistance than the other two alloys. [ABSTRACT FROM AUTHOR]

• SLM-fabricated 430 FSS exhibits significant anisotropy. • SLM-fabricated 430 FSS contains second-phase oxides and high dislocations. • SLM-fabricated 430 FSS exhibits excellent strength with limited plasticity. • SLM-fabricated 430 FSS shows cleavage fractures. This study investigates the microstructure and mechanical properties of 430 ferritic stainless steel (FSS) fabricated via the selective laser melting (SLM) process. The mechanical properties and fracture morphologies of SLM-fabricated 430 FSS and conventional 430 FSS were compared in this paper. It was found that 430 FSS produced by SLM exhibits significant microstructural anisotropy, with higher dislocation density and the presence of oxides of silicon, manganese and aluminum. Regarding mechanical properties, 430 FSS fabricated via SLM process displays higher tensile strength and yield strength, as well as superior product of strength and elongation (PSE) and yield ratio, compared to those produced by conventional methods. Fracture morphology analysis revealed that SLM-fabricated 430 FSS primarily exhibited characteristics of cleavage fractures, whereas conventional 430 FSS showed typical features of ductile fractures. [ABSTRACT FROM AUTHOR]