Peiqing La

Developing stable alumina-based scales is critical for alumina-forming austenitic (AFA) alloys exposed to highly basic molten carbonates. However, the inherently sluggish diffusion of Al in austenite often limits the establishment of continuous protective layers. Herein, a thermomechanical treatment (TMT) strategy is proposed to enhance short-circuit diffusion pathways and promote selective Al oxidation in a Li–Na–K carbonate melt at 700 °C. After 90% cold rolling, annealing at 800 °C and 1000 °C generated two distinct microstructural states characterized by different grain boundary types, dislocation densities, and NiAl precipitate populations. The 800 °C-annealed alloy exhibits a significantly lower steady-state corrosion rate (~62 μm/yr) compared with the coarse-grained 1000 °C counterpart. EBSD and TEM analyses reveal that ultrafine grains, abundant low-angle boundaries, and finely dispersed NiAl precipitates provide efficient fast-diffusion channels and local Al reservoirs, enabling rapid formation of a continuous LiAlO₂/Al₂O₃ inner layer. In contrast, insufficient Al flux in the 1000 °C microstructure results in extensive internal oxidation and growth of a thick, non-protective LiFeO₂/NiO scale. These findings demonstrate that controlling the defect and grain-boundary structure via TMT is an effective route to overcome Al diffusion limitations and improve the molten-carbonate corrosion resistance of AFA alloys.

Fe–Al alloys possess excellent high-temperature strength, oxidation resistance, and corrosion resistance, but their inadequate room-temperature plasticity remains a significant challenge. When Fe₃Al was alloyed with specific elements (Cr, V, Ni, Mo), it was found that chromium significantly enhanced dislocation mobility and grain boundary (GB) deformation. Further nanostructuring of the Fe–Al–Cr alloy through grain refinement revealed a transition in the strength-ductility balance at a critical grain size of 9 nm, marking the breakdown point of the Hall–Petch relationship. For grain sizes larger than 9 nm, the alloy exhibited classical Hall–Petch behavior, governed by deformation twinning and dislocation activity. In contrast, for grain sizes smaller than 9 nm, the deformation mode deviated from conventional Hall–Petch scaling, transitioning to mechanisms dominated by GB sliding and grain rotation. Additionally, grain coalescence and GB migration led to boundary thinning. Temperature played a crucial role in mechanical properties: elevated temperatures increased the proportion of GB atoms while reducing the density of atoms within the grains, thereby delaying dislocation nucleation at GBs.

To investigate the evolution of microstructure and mechanical properties in cold-rolled sheets of Ferritic Stainless Steel (FSS) during annealing, a series of annealing tests were performed on 00Cr21CuTi at different temperatures of 930, 990, and 1050 °C. The changes in microstructure at these annealing temperatures were characterized by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron back-scattered diffraction (EBSD). The influence of annealing temperature on mechanical properties was assessed utilizing a universal tensile testing machine and a laser confocal microscope. The results indicated a gradual decrease in yield strength and tensile strength with increasing annealing temperature, whereas elongation exhibited an upward trend. At an annealing temperature of 930 °C, the yield strength, tensile strength, and elongation of the steel were 251 MPa, 409 MPa, and 30.9%, respectively, with a high product of strength plastic 12.64 GPa·%. This result represented an optimal balance between comprehensive strength and plasticity.

As concentrated solar power (CSP) systems evolve, the new generation of CSP systems will utilize chloride molten salts, which are cost-effective and have high operating temperatures, but are highly corrosive. In order to reduce the corrosiveness of chloride salts, we investigated the addition of different levels of Mg to chloride salts to study the effect on corrosion. In this paper, the corrosion behavior of 310S stainless steel with aluminum in high-temperature molten salt NaCl-KCl-MgCl₂ was studied. By adding different contents of magnesium corrosion inhibitor, the corrosion mechanism and the effect of the corrosion inhibitor were explored. The results show that the lowest corrosion rate of 6.623 mm/y was obtained for the aluminum-formed 310S with 0.05 wt.% Mg. However, the corrosion rate rises when the Mg content exceeds 0.05 wt.% compared to the corrosion rate of corroded specimens without Mg. Changing the added Mg content does not affect the corrosion products. For 310S stainless steel with aluminum, its corrosion inhibition was best achieved by adding 0.05 wt.% Mg to the chloride molten salt.

Solar and radiative warming are smart approaches to maintaining the human body at a metabolically comfortable temperature in both indoor and outdoor scenarios. Nevertheless, existing warming textiles are ineffective in frigid climates because the solar absorption of selective absorbing coating is significantly reduced when coated on rough textile surface. Herein, for the first time, high‐entropy nitrides based spectrally selective film (SSF) is introduced on common cotton through a one‐step magnetron sputtering method. The well‐designed refractive index gradient enables destructive interference effects, offering a roughness‐insensitive high solar absorptance (92.8%) and low thermal emittance (39.2%). Impressively, the solar absorptance is 9.1% higher than the reported best‐performing selective nanofilm‐based textile. As a result, such a textile achieves a record‐high photothermal conversion efficiency (82.2% under 0.6 suns, at 0 °C). This textile yields a 3.5 °C drop in the set‐point of indoor air‐conditioner temperature. Besides, in a winter morning with an air temperature of 7.5 °C, it warms up the human skin by as large as 12 °C under weak sunlight (350 W m⁻²). More importantly, such a superior radiative warming performance is achieved by engineering the widely used cotton without compromising its breathability and durability, showing great potential for practical applications.

In this work, a large ingot of micro-nano structure 2507 duplex stainless steel was prepared in a single step using the aluminothermic reaction method. Chromium having different excess fractions were added to reaction powders to make up for evaporation loss, and the results show that the composition and structure of 2507 duplex stainless steel with a chromium excess ratio of 70% are satisfactory. The volume fraction of nanocrystalline in as-cast alloy was 41% and the average grain size was 34 nm. Additionally, the anticipated steels were rolled roughly with deformation of 40% at 1000 °C and followed by fine rolling with deformation of 30, 50 and 70%, separately, at 800 °C. Then, the effects of rolling deformation and precipitation on mechanical properties were studied in detail. Compared with the as-cast alloy, there was no phase transformation in the alloys with deformation of 30 and 50%, and they were still composed of γ and α phases, whereas the σ phase appeared in the alloy with deformation of 70%. When the deformation was 50%, the rolled alloy achieved the best performance, and the tensile strength, yield strength, and elongation were 912 MPa, 523 MPa, and 24.3%, respectively.

The key to the new generation of solar thermal power plants is to increase the operating temperature of molten salt to 800°C, and change the heat transfer medium from nitric acid mixed salt to chlorine mixed salt, so as to significantly reduce the cost of power generation. Therefore, the alloy material’s resistance to high temperatures and fusible chloride salt is one of the core technologies for the successful implementation of concentrated solar power (CSP) technology. In this study, the aluminum-forming alloy (AFA) 310S for the heat storage tank was prepared by the aluminum-thermal reaction casting method. The hot corrosion behavior and mechanism of AFA 310S in chloride molten salt at 800°C were studied by static immersion etching for 600 h. AFA 310S exhibits good thermal corrosion properties in KCl 20.4 wt% + MgCl₂-55.1 wt% + NaCl 24.5 wt%. The results indicate that compared with commercial 310S, AFA 310S has better oxidation resistance at 800°C. At the initial stage of corrosion, dense Cr₂O₃ and continuous Al₂O₃ passivation films are formed. At the same time, MgO-rich oxidation products were produced in the outermost layers of the two alloys during the 600 h process. Over time, however, the damage caused by chlorine became more apparent, mainly due to the “oxidation-chlorination” process of the metal. A large number of cavities and cracks on the surface are formed, and the oxide layer has obvious spalling. When the Al element was added into the alloy, the dense passivation film could be formed after 120 h of corrosion with the stronger corrosion resistance. The experiment simulated the corrosion behavior in the worst environment, such as air, unoxidized alloy, molten salt without corrosion inhibitor, etc. By weight loss calculation, commercial 310S plate is completely unsuitable for CSP plant. The corrosion rates of the two alloys are compared as follows: commercial 310S > AFA 310S. To sum up, AFA 310S has a good application prospect in concentrated solar power.

A laminated structured 2205 duplex stainless steel (DSS) with graded grain size was prepared via aluminothermic reaction and subsequent hot rolling with deformation of 80% at 1000°C, and its mechanical properties, strengthening and toughening mechanism were studied. Our materials have extraordinary elongation of 54% and high tensile strength of 990 MPa. The lamellar structure is characterized with heterogeneous lamella austenite (with nano-grain, ultrafine grain, micro-grain and nano-twin) and ferrite (with ultrafine grain and a proper amount of micro grain) coalesced alternately. The high strength is attributed to strengthening of complex grain (distribution from nanoscale to microscale) and interfaces arising from hierarchical and laminated dual-phase heterogeneous structure and distribution. The unusual high ductility is thought to be mainly attributed to the lamellar structure and dislocation hardening.