Explore the vast range of titles available.

For 5000 years, metals have been mankind's most essential materials owing to their ductility and strength. Linear defects called dislocations carry atomic shear steps, enabling their formability. We report chemical and structural states confined at dislocations. In a body-centered cubic Fe–9 atomic percent Mn alloy, we found Mn segregation at dislocation cores during heating, followed by formation of face-centered cubic regions but no further growth. The regions are in equilibrium with the matrix and remain confined to the dislocation cores with coherent interfaces. The phenomenon resembles interface-stabilized structural states called complexions. A cubic meter of strained alloy contains up to a light year of dislocation length, suggesting that linear complexions could provide opportunities to nanostructure alloys via segregation and confined structural states.

This work presents insights into the manganese influence on the driving force and bainite transformation kinetics. Three different medium-Mn steels were subjected to theoretical calculations and dilatometric study in order to determine the Mn impact on bainite formation. The theoretical approach shows that the increase of manganese leads to a lower bainite fraction formed during the isothermal stage. This implicates the carbon enrichment of the austenite during thermal treatment. The less bainite is formed, the higher is the fraction of residual austenite which enrichment of carbon is globally low. Meanwhile, the manganese influences the incubation and transformation time. As the manganese content increases, the incubation period and formation time of bainite are longer because the chemical driving force essential to start and complete austenite into bainite transformation decreases. This was proved by theoretical calculations and dilatometric analysis, which show that even a small increase in manganese content leads to a longer time necessary to occur the bainitic transformation. For the steel containing 5% manganese, the driving force was too small that the transformation could occur even after 3 h. Additionally, the XRD analysis was conducted to determine the retained austenite fraction and its carbon enrichment. These results were compared with the theoretical values to determine the accuracy of the applied model.

Palladium hydride (PdH x ) metallenes are efficient electrocatalysts for the oxygen reduction reaction (ORR) due to their high atomic utilization and optimized oxygen binding energies modulated by interstitial hydrogen. However, their practical application is restricted by the highly unstable nature of interstitial hydrogen at working temperatures around 353 K. Here, we report that the use of Mn effectively locks hydrogen atoms within the Pd metallenes lattice, resulting in high alkaline ORR performance across a temperature range of 303–353 K. In contrast, the ORR activity of PdH x metallenes declines sharply with increasing temperature. At 353 K, the mass activity of PdMnH x metallenes at 0.95 V reaches 1.41 A mg − 1 , which is 14.1 times higher than that of PdH x metallenes. Multiple spectroscopic analyses and theoretical calculations reveal that strong electronic interactions within the immiscible Pd-Mn alloy are critical for locking interstitial hydrogen, thereby enhancing the ORR activity under high temperatures. The authors present a Mn incorporation strategy to enhance the stability of PdH x metallenes by locking interstitial H atoms via strong electronic interactions in the immiscible alloy, resulting in an improved alkaline oxygen reduction reaction activity and stability at working temperature around 353 K.

The study systematically examined how Mn impacts the precipitates and mechanical properties of 6082 aluminum alloy during the peak state of artificial aging following various natural aging durations, elucidating the underlying mechanisms. It is found that α-Al(Mn,Fe)Si precipitated during homogenization is less in amount in the alloy with lower Mn content, resulting in the less consumption of Si and a lower real Mg/Si ratio to create a relatively Si-rich environment in matrix. The Si-rich environment promotes the nucleation of the precipitates, so that the low Mn alloy precipitates more and finer precipitates in the artificial aging process, and has higher strength than the high Mn alloy. Additionally, it is also found that with the increase of natural aging time, the precipitates of 6082 aluminum alloy are significantly coarsening, and the alloy with lower Mn content can better resist the coarsening process of the precipitates, so that the strength of the alloy decreases more slowly than that of higher Mn alloys, and the negative effects of natural aging are lighter.

This study investigates the microstructural behavior of laboratory-produced Al–Mg–Si(X)–Mn aluminum alloys, focusing on the influence of varying Si content during biaxial hot tensile testing. Alloys with Si contents of 0.7%, 0.9%, and 1.3% were subjected to biaxial deformation at temperatures of 200 °C, 300 °C, and 400 °C. Using digital image correlation analysis, the impact of Si content on microstructural evolution under biaxial tensile loading was analyzed. Force–displacement analysis revealed a consistent inverse relationship between temperature and the maximum force required to initiate strain. At the temperature of 200 °C, the Al–Mg–Si(1.3)–Mn alloy required a maximum force of 1500 N, while at the temperature of 400 °C this force decreased to 900 N. The degree of anisotropy varied, with higher Si alloys exhibiting increased resistance to deformation in the transverse direction. In particular, the Al–Mg–Si(1.3)–Mn alloy showed pronounced strain anisotropy, with large major true strain φ 1 values reaching up to 0.32 at 400 °C, compared to 0.26 at 300 °C and 0.2 at 200 °C. Microstructural analysis using electron backscatter diffraction (EBSD) and energy dispersive X-ray spectrometry (EDS) showed minimal changes at low temperatures, while increased dislocation density and grain boundary distortion were observed at elevated temperatures. The β-Mg 2 Si precipitates, influenced by Si content and temperature, significantly affected the mechanical properties. In the Al–Mg–Si(0.7)–Mn alloy, precipitates were predominantly 1–3 µm in diameter, whereas in the Al–Mg–Si(1.3)–Mn alloy, precipitates grew to 4–8 µm at higher Si content. These findings provide critical insights into the mechanical response and deformation mechanisms of aluminum alloys under biaxial tensile conditions, essential for optimizing material performance in engineering applications. Graphical abstract

T6 aging, involving solution treatment and artificial aging, is a widely adopted strengthening method for magnesium alloys due to its proven effectiveness. However, the integration of three or more sequential thermal treatments has been explored only sparingly, primarily due to the challenges associated with optimizing such multi-parameter processing systems. This study demonstrates that integrating a 12 h deep cryogenic treatment (DCT) before aging in a Mg–Al–Ca–Mn alloy optimizes mechanical performance, achieving a tensile strength of 343 MPa and 27.3% elongation. Microstructural analysis, based on electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM), reveals that the strength enhancement results from ~29 nm precipitate refinement, elevated dislocation density, and nanoscale sub-grain formation, while the ductility gains stem from the activation of non-basal slip systems and the suppression of microcrack propagation. These synergistic mechanisms enable superior strain accommodation, providing a clear framework for DCT-enabled sequential heat treatment design in high-performance magnesium alloys.

Directed energy deposition (DED) provides the possibility of high-throughput synthesis by controlling the multi-channel powder feeders. However, the compositional accuracy of the targeted alloy is of concern due to the difficulty of adjusting the proportions. In this work, we present a method to improve the adjustment accuracy of the high-throughput DED technology by replacing the elemental powder with pre-alloyed powder, and binary Al–Mn alloys with different compositions were synthesized with a composition step of 1 wt.%. The effect of Mn content on the microstructure and mechanical properties of the alloys was characterized and analyzed, and the relationship between the Al 6 Mn phase and the yield strength was established. The results showed that the microstructures of DED-ed Al–Mn alloys are composed of Al and Al 6 Mn phases with Mn contents in the range of 2–10 wt.%. The Al–Mn alloy reaches a tensile strength of 165 MPa and maintains an elongation of 9% at Mn content of 4 wt.%. The improved controlling accuracy of composition step to 1 wt.% by pre-alloyed powder in this work provides a paradigm for high-throughput discovery of high-performance alloys.

Segregation is a type of harmful defect, especially for strips with high alloying content aluminum alloys produced by twin-roll casting, which seriously inhibits the mechanical properties. Mo is often used for the refiner in aluminum alloys, and, in this study, the effect of Mo on the segregation behavior of Al-Mg-Si-Mn alloy produced by twin-roll casting is investigated. The results show that the addition of Mo can effectively reduce the secondary dendrite arm spacing (SDAS) and refine the solidification microstructure. More importantly, the segregation behavior in the thickness direction of the cast-rolled sheet is significantly weakened after the addition of Mo. Considering the principle of segregation formation, the secondary dendrite arm spacing in the center region decreases sharply from 33 to 16 μm, which is beneficial for more solute elements to enter the Al matrix, thus improving the redistribution coefficient of the solute elements. Therefore, in the final stage of solidification, there are fewer solute atoms in the residual liquid phase, which leads to the alleviation of segregation behavior. The research on segregation behavior in this paper is of great significance for the effective control of segregation and the preparation of high-quality aluminum alloy sheets by twin-roll casting.

Cast Al-Cu-Mg-Mn alloy, prepared by differential pressure casting method, was quenched at 530 °C and aged at 170 °C. The effect of aging time on the corrosion resistance of the Al alloy was investigated in 3.5 wt.% NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy tests. The results indicated that the aging time had great influence on the distribution of the Al 2 Cu phase. A small amount of fine second phase had precipitated along grain boundaries to strengthen the alloy when the aging time was 6 h. Extended aging time led to the rapid growth of the second phase. Pitting corrosion occurred at the interface between the Al 2 Cu phase and α-Al matrix in 3.5wt.% NaCl solution. The Al 2 Cu phase with a small size easily fell off to form corrosion pits during the corrosion process, leading to more serious pitting corrosion. However, a network-like Al 2 Cu phase prevented its falling off, improving pitting corrosion resistance.

NRC publication: Yes