The ternary-based Fe-24Mn-3Cr alloy has superior mechanical properties based on an attractive combination of high strength and ductility, with long-term environmental stability in highly corrosive environments compared to conventional ferritic steel alloys. This study reports that the environmental instability caused by the rapid electrochemical corrosion kinetics on the surface of conventional high Mn-bearing ferrous alloys could be overcome by a combination of high Mn–low Cr-balanced Fe and their synergistic interactions. In contrast to Cr-free Mn-bearing alloys, the high Mn–low Cr-bearing alloy showed comparatively lower corrosion kinetic parameters, without a continuously increasing trend, and higher polarization resistance according to electrochemical polarization and impedance spectroscopy measurements. Moreover, the rate of degradation caused by erosion–corrosion synergistic interaction under erosion–corrosion dynamic flow conditions was the lowest in the high Mn–low Cr-bearing alloy. These surface-inhibiting characteristics of the alloy were attributed primarily to the formation of a bilayer scale structure consisting of inner α-Fe2−xCrxO3/outer FexMn3−xO4 on the surface.

To expand the industrial applicability of strong and ductile high Mn-Low Cr steel, a deeper understanding and mechanistic interpretation of long-term corrosion behavior under harsher environmental conditions are needed. From this perspective, the long-term corrosion behaviors of 24Mn3Cr steel under acidic aqueous conditions were examined through a comparison with conventional ferritic steels using the electrochemical measurements (linear polarization resistance and impedance), and immersion test followed by the metallographic observation of corrosion morphologies. In contrast to conventional ferritic steels, 24Mn3Cr steel, which had the lowest corrosion resistance at the early immersion stages (i.e., the highest corrosion current density (icorr) and lowest polarization resistance (Rp)), showed a gradual increase in corrosion resistance with prolonged immersion. Owing to the slow formation kinetics of (Fe,Cr)-enriched oxide scale, a longer incubation time for ensuring a comparatively higher corrosion resistance is required. On the other hand, conventional ferritic steels had an oxide scale with less densification and a lower elemental enrichment level that did not provide an effective anti-corrosion function. From the results, this study can provide significant insight into the industrial applicability of the high Mn-low Cr steel by providing the mechanistic interpretation of corrosion behaviors in acidic aqueous environments.

The utility of a novel digital image processing technique for automatic detection and separation of cracked constituent particles was applied to quantitatively characterize the microstructural damage on Fe-rich intermetallic particles that were cracked in a 7075 Al-alloy. This cracking of the Fe-rich intermetallic particles was due to a function of strain under uniaxial tension, compression, and torsion. The comparison of the data on the strained samples revealed that at tensile strain, the number fraction of the cracked Fe-rich particles was significantly higher than those at torsion while the compression strains and the average volume of the cracked Fe-rich particles increased when the strain increased. The percentage-cracked particles had a linear relationship with all of the strains for all of the loading conditions. Significant rotations of Fe-rich intermetallic particles occurred during the deformation of this alloy under torsion. These rotations tended to align themselves along the direction of applied/induced tensile stretch, which in turn affected the progression of damage due to particle cracking.

The spatial arrangement and heterogeneity of microstructural features, in particular, porosity in the cast microstructures, adversely affect the mechanical properties, and consequently lead to significant variability in the properties. Clearly, successful applications of cast alloys require production of castings that exhibit reproducible mechanical responses and low variability in the properties. Therefore, it is essential to thoroughly understand how the spatial arrangement and heterogeneity of porosity govern the mechanical properties. In this respect, new techniques that can simulate the microstructures with different degrees of spatial clustering and arrangement of porosity are presented. New parameters to describe different degrees of microstructural simulations were developed and corresponding virtual 2D microstructures were created. The simulated microstructures were implemented in a Finite Elements (FE) framework in order to study and predict the mechanical properties, which show a good agreement with the experiments.