Metals

The cold creep of titanium alloy sheets has long been a critical issue for marine equipment. So far, the orientation dependence of such behavior remains far from understood, threatening the dimensional stability and service safety of long-term load-bearing structures. In this study, the early-stage room-temperature creep behavior of a near-α Ti6321 (Ti80) alloy sheet was systematically investigated along the rolling direction (RD), 45-degree direction, transverse direction (TD), and normal direction (ND). The sheet exhibited pronounced room-temperature creep anisotropy among the four orientations. The creep strain was highest in the RD specimen, followed in descending order by the ND, TD, and 45-degree specimens, and the creep rate followed the same ranking, clearly confirming the existence of creep anisotropy. Slip-system analysis was conducted to clarify the deformation mechanism. Basal and prismatic slip were readily activated in the RD and ND specimens and provided the principal contributions to creep strain. In contrast, prismatic slip was more difficult to activate in the 45-degree and TD specimens, where pyramidal slip accounted for a larger fraction. The lower creep strains in these orientations resulted from impeded slip transfer and dislocation transmission across grain boundaries. The origin of the creep anisotropy was attributed to the distinct activation of dislocations owing to the varied orientation. The principal mechanisms responsible for the differences in creep rate among specimens with different orientations are also discussed. The correlation between creep anisotropy and the actual dislocation motion as well as the dynamic variation in true stress is established, which benefits the accurate dimension controlling of titanium components.

The rapid development of the new energy industry has led to a significant increase in the demand for lithium. The electrolytic aluminum industry generates a large quantity of lithium-bearing waste slag each year. Long-term stockpiling of this slag not only poses a threat to the ecological environment but also results in a waste of valuable resources. This study proposes a process to extract lithium from electrolytic aluminum slag (EAS) via mild AlCl₃ leaching and subsequently prepare lithium carbonate products. The leaching kinetics of Li⁺ during lithium extraction were systematically investigated, and the Li₂CO₃ preparation process was optimized accordingly. The results show that the leaching process for lithium extraction from EAS is a solid–liquid two-phase reaction process, which conforms to the unreacted shrinking core model. The Li⁺ leaching process exhibits temperature-dependent rate-controlling characteristics. The mixed control equation best describes the 80–95 °C data, and the rate-controlling step at 60–70 °C cannot be assigned. At 95 °C, under different AlCl₃ concentration conditions, the Li⁺ leaching process is mainly controlled by mixed diffusion. The lithium-bearing filtrate obtained after leaching was subjected to modulated aluminum precipitation, evaporative crystallization, and carbonation for lithium precipitation to obtain a Li₂CO₃ product with a purity of 98.6%, which complies with the relevant national standards for industrial-grade lithium carbonate. This research provides theoretical guidance and data support for the industrialization of extracting lithium from electrolytic aluminum carbon slag and preparing lithium carbonate products.

Al-Cr-Fe-Ni eutectic high-entropy alloys (EHEAs) with an FCC + B2 dual-phase microstructure are promising candidates for high-temperature structural applications, yet the competitive oxidation behavior between the two phases at elevated temperatures remains unclear. In this work, four Al_xCrFeNi_3−x (x = 0.75, 0.8, 0.85, 0.9) EHEAs are prepared by vacuum arc melting, and their oxidation resistance at 850 °C is evaluated for up to 150 h. All alloys possess an FCC + B2 eutectic microstructure. With increasing Al content, the B2 phase fraction rises from 20.5% to 66.4%, and the microstructure evolves from an FCC matrix with dispersed B2 islands, via a lamellar eutectic transition, to a B2 matrix with isolated FCC islands. The oxidation kinetics of all alloys follow a parabolic rate law, and the Al_0.85 and Al_0.9 alloys exhibit the best oxidation resistance with a mass gain of only 0.49 mg/cm² after 150 h of oxidation. The Al-rich B2 phase preferentially oxidizes to form Al₂O₃-rich oxide, while the Fe/Cr/Ni-rich FCC phase forms Cr₂O₃-rich oxide and spinel oxides. The oxide scale evolves into a bilayer structure with a dense continuous Al₂O₃-rich oxide inner layer and a Cr/Fe-rich oxide outer layer. An Al-depleted layer accompanied by B2-to-FCC decomposition forms in the subsurface, and its thickness decreases with rising Al content. The superior oxidation resistance of high-Al EHEAs stems from the synergistic effect of the B2 phase acting as an Al reservoir and eutectic interfaces acting as a possible short-circuit diffusion pathway, which jointly promote the formation of a continuous protective Al₂O₃-rich oxide scale.