By altering the temperature and duration of intercritical annealing (IA), the mechanical stability of retained austenites (RAs) is intentionally regulated in newly designed cold-rolled medium manganese steel of Fe-0.4C-7Mn-3.2Al (in wt%). Consequently, a novel combination of ultimate tensile strength (UTS) and total elongation (TE) (e.g., 1118 MPa and 67%) is obtained in duplex steel, and the corresponding product of UTS and TE can reach 75 GPa%. Both twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP) take effect step by step during deformation and are conducive to the outstanding properties.
Aqueous rechargeable zinc‐ion batteries (ZIBs) have attracted burgeoning interests owing to the prospect in large‐scale and safe energy storage application. Although manganese oxides are one of the typical cathodes of ZIBs, their practical usage is still hindered by poor service life and rate performance. Here, a MnO2–carbon hybrid framework is reported, which is obtained in a reaction between the dimethylimidazole ligand from a rational designed MOF array and potassium permanganate, achieving ultralong‐cycle‐life ZIBs. The unique structural feature of uniform MnO2 nanocrystals which are well‐distributed in the carbon matrix leads to a 90.4% capacity retention after 50 000 cycles. In situ characterization and theoretical calculations verify the co‐ions intercalation with boosted reaction kinetics. The hybridization between MnO2 and carbon endows the hybrid with enhanced electrons/ions transport kinetics and robust structural stability. This work provides a facile strategy to enhance the battery performance of manganese oxide‐based ZIBs.
The microstructures and mechanical properties of Fe–0.35C–3.2Al–5Mn (in wt%, same later) hot‐rolled medium‐manganese steels are systematically investigated. The results show that ultrafine‐grained duplex phases with bimodal morphologies of lath and equiaxed are obtained with intercritical annealing at 750 °C for 1 h, along with ultimate tensile strength of 950 MPa and total elongation of 71.2%, attributed to the dislocation slip and deformation of ferrite matrix, accompanied by the synergetic twinning of retained austenite plus transformation of retained austenite to martensite. The newly developed medium‐manganese steels, which exhibit an excellent product of ultimate tensile strength and total elongation of 67.6 GPa·%, demonstrate great practical applications.
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