In this paper, the results of a study on the influences of different morphologies, types, and sizes of inclusions on the fatigue lives of 20CrMnTi are reported. The results show that the addition of the rare earth element Ce can lead to the formation of spherical CeAlO₃-TiN inclusions in 20CrMnTi. The fatigue performance of 20CrMnTi-Ce was significantly improved compared to that of 20CrMnTi. Using the “edge-to-edge matching” crystallographic theory, CeAlO₃ was validated as a suitable hetero-nucleus core for TiN, and the following best orientation relationships between them were determined: [010]TiN//[2$\overline{1}\overline{1}$1] CeAlO₃&(002) TiN//${\left(11\overline{2}1\right)}_{{\mathrm{C}\mathrm{e}\mathrm{A}\mathrm{l}\mathrm{O}}_3}$. The fatigue cycle times of 20CrMnTi-Ce range up to 10⁷, and this value is higher than that of 20CrMnTi without Ce. As the size of the TiN inclusions increases, the maximum stress of the steel matrix also increases. Also, the high-stress and low-life regions noticeably increase, thus increasing the possibility of a fatigue fracture. Under the same sizes of inclusions, the high-stress and low-life regions of square TiN are larger than those of circular TiN.

A series of ionic liquids based on trifluoroacetic acid, namely, [C_nmim][TFA] (n= 2, 3, 4, 5, 6) (1-alkyl-3-methylimidazolium trifluoroacetate), were designed and synthesized.

The morphologies and sizes of TiN inclusions in gear steel 20CrMnTi have a significant impact on its service performance. This paper selects rare earth Ce to modify TiN inclusions in 20CrMnTi. The inclusions are analyzed by SEM (scanning electron microscope), EBSD (electron back-scattered diffraction), EDS (energy disperse spectroscopy), and OTS statistical software, and Thermo-Calc software is used to calculate the inclusion formations. The inclusions of MgAlO₄-Ce and CeAlO₃ can be formed when rare earth Ce is added into 20CrMnTi, which becomes TiN nucleation core after precipitation. Without the addition of rare earth Ce, square TiN inclusions ranging from 2 to 5 μm account for 60% of the total inclusions in 20CrMnTi. After adding rare earth Ce, the TiN inclusions in 20CrMnTiCe account for 36.7% of the total inclusions. Due to the new phase formations of MgAlO₄-TiN and CeAlO₃-TiN with sizes less than 2 μm, the titanium-containing inclusions are refined. Fatigue tests are conducted on the steels before and after the addition of Ce. The average fatigue lives of 20CrMnTi do not reach 10⁷ times, and the deviations between the maximum and minimum fatigue lives are great. Large-sized TiN are the main inclusions that affect the fatigue performance of 20CrMnTi. The average fatigue lives of 20CrMnTiCe exceed 10⁷ times, and the deviations of the fatigue lives are smaller than those of 20CrMnTi.

Porous 316L stainless steel has a low density and high specific surface area, and is easy to process due to the large number of pores within it, making it ideal for applications such as piping in the chemical and food industries, as a medical tool, or as a fuel cell pole plate material. Nitriding treatment can further improve the hardness and strength of porous stainless steel. In this paper, a method combining vacuum sintering and nitriding treatment was proposed, i.e., 316L stainless steel powder was used as the raw material, and porous 316L was sintered in a vacuum tube furnace, in which the porous stainless steel was nitrided with nitrogen gas during the cooling process. In the research process, thermodynamic calculation and differential thermal analysis were used to determine the optimum nitriding temperature range of 700 °C~850 °C and nitriding pressure of 0.4 MPa~0.8 MPa. With the increase in nitriding temperature and pressure, the nitrogen content in the sample increased, and the nitrogen content of porous 316L stainless steel after nitriding was 0.03%~0.86%. The results show that nitrogen exists exclusively in solid solution at nitriding temperatures of 700 °C and 750 °C. At nitriding temperatures of 800 °C and 850 °C, the nitrogen existed in both solid solution and chromium nitride (CrN), and the Vickers hardness at 0.08 MPa and 850 °C was 135 HV, which was 2.82 times higher than that before nitriding. The compressive strength of the specimens was maximum at a nitriding pressure of 0.04 MPa and 850 °C. The corrosion resistance of the specimens is optimized when the nitriding pressure is 0.04 MPa and the temperature is 800 °C.

Liquid–liquid extraction of Eu³⁺ from aqueous solution with 4-oxaheptanediamides (OHAs) as extractant into room temperature ionic liquids (RTILs) of 1-alkyl-3-methylimidazolium hexafluorophosphate (C_nmim⁺PF₆^–, n = 4, 6 and 8) was investigated. The strong affinity of OHAs to Eu³⁺ was observed in the present C_nmim⁺PF₆^– system. The extraction was assumed to proceed by cation-exchange mechanism and formed a 4:1 complex of the OHA extractants and Eu³⁺ in C₄mim⁺PF₆^– system. The preferable composition of extracted species was presumed to be Eu(OHA)₄(H₂O)₄(PF₆)₃ by ESI-MS.