Transactions of Nonferrous Metals Society of China (中国有色金属学报)•2026•DOI: 10.1016/S1003-6326(26)67066-5
Oxidation roasting of bastnaesite was conducted to evaluate its impact on surface characteristics and flotation behavior. Experiments varied temperature, time, and O2 concentration. Increasing temperature promoted thermal decomposition, yielding Ce7O12, RE2O3, and REF3 as main phases. The Ce oxidation degree and REO grade of roasted products exceeded 85.00%. Roasting induced long, narrow, nearly parallel cracks within particles, increasing porosity and causing partial fragmentation. During flotation, dissolved rare earth ion concentration increased significantly, and surface hydrolysis formed rare earth hydroxyl compounds. Complete decomposition raised the required collector dosage to achieve recovery above 85.00%. This increase is attributed to enhanced particle wettability, altered collector adsorption, and deeper penetration into the porous structure. The findings provide a basis for optimizing flotation circuits treating roasted bastnaesite, particularly in iron-bearing rare earth deposits where pyrometallurgical pretreatment is employed.
Journal of Central South University•2026•DOI: 10.1007/s11771-026-6237-y
Intergrown ferromanganese ore resources are typical strategic mineral resources with huge reserves and abundant hematite, pyrolusite, and other valuable minerals, which is of great significance for its development and utilization. This paper adopts a combination of phase transformation and magnetic separation to explore the phase transformation mechanism of Fe minerals and Mn minerals during the roasting process. The analysis of the properties of the raw ore shows that the Fe-containing and Mn-containing minerals of the intergrown ferromanganese ore are hematite and pyrolusite, respectively. The optimal conditions for controlling the mineral phase were obtained, including roasting temperature of 600 ℃ for 30 min, and a grinding fineness of <0.074 mm accounting for 50%. Meanwhile, a Fe grade of 61.05% with a recovery of 80.77%, and a Mn grade of 61.60% with a recovery of 87.81% were acquired. The precise mineral phase transformation (MPT) could be realized via adjusting the roasting conditions. Hematite is transformed into magnetite, while pyrolusite is transformed into manganosite, and then they were effectively separated and concentrated via magnetic separation.
China Foundry•2025•DOI: 10.1007/s41230-025-4146-6
The phase constitution, microstructure, damping capacity, and mechanical properties of as-cast AlxCrFe3Ni (x=0.5, 0.52, 0.54, and 0.56, respectively) medium entropy alloys were investigated. It is found that the volume fraction of BCC phase increases while that of FCC decreases with increasing the Al content. When the content of Al is 0.54, the alloy is composed of 82.1vol.% BCC matrix and 17.9vol.% FCC phase. Wherein the FCC phase is distributed on the BCC matrix, forming a structure where the hard BCC matrix is surrounded by soft FCC phase. This results in a hindering effect on the propagation process of vibration waves. The damping performance of Al0.54CrFe3Ni alloy, characterized by an internal friction of Q-1 is as high as 0.059, is higher than that of most FeCr damping alloys. The volume fraction of the BCC phase and the peculiar distribution of the FCC phase are identified as the key factors affecting the damping capacity. In addition, the Al0.54CrFe3Ni alloy exhibits a high yield strength of 811.16 MPa.
Journal of Central South University•2025•DOI: 10.1007/s11771-025-6126-9
After the hot deformation sample of Ti-10V-2Fe-3Al alloy was treated by solid solution in the α+β two-phase region, the coarse β grains that often appeared in the β single phase region were observed in the local region, indicating that the abnormal grain growth occurred in the local microstructural region, and the macrostructure also showed abnormally coarse grains (ACGs). The dynamic recrystallization (DRX) behavior of Ti-10V-2Fe-3Al titanium alloy was systematically investigated through hot compression tests on the Gleeble-3800 system. The DRX model of β grains was established, and the quantitative correlation between DRX characteristics and the appearance of ACG was clarified. Based on these results, a numerical simulation platform was developed to realize the visual prediction of ACG distribution. The results show that the increase of deformation temperature and the decrease of strain rate both contribute to a significant increase in the grain size (dDRX) and volume fraction (XDRX) of DRXed grains. However, the proper XDRX and smaller dDRX at low deformation temperature and high strain rate make the macro and microstructure show ACGs after solid solution. Interestingly, if the DRX degree is excessive or insufficient, ACGs cannot be produced, indicating that ACGs are solid solution products based on the appropriate DRX degree. According to the flow curves and statistical results of microstructure, the quantitative model of DRX kinetics and DRX grain size model were constructed, and the quantitative criterion model that is related to the formation of ACG with grain size (dDRX) and volume fraction (XDRX) of DRXed grains as the key parameters was established, i. e., dDRX£2.60 μm, 72.5%£XDRX£87.9%. By integrating the subroutine of coarse grain criterion, the isothermal compression process of cylindrical samples and the actual die forging process of H-shaped parts were simulated by DEFORM-3D software of finite element (FE), respectively, and the visual prediction of the distribution of macroscopic ACGs was realized. There is a good consistency between the tested results and the simulated results, indicating a strong correlation between macroscopic ACGs and microscopic DRX.
Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报)•2025•DOI: 10.1007/s12613-024-3053-y
Hydrogen-based mineral phase transformation (HMPT) technology has demonstrated its effectiveness in separating iron and enriching rare earths from Bayan Obo refractory ores. However, further research is needed to clarify the phase composition and floatability of rare earths obtained after HMPT owing to the associated phase transformations. This study explored the mineralogical characteristics and separation behavior of rare earths in HMPT-treated iron tailings. Process mineralogy studies conducted via BGRIMM process mineralogy analysis and X-ray diffraction revealed that the main valuable minerals in the tailings included rare-earth oxides (9.15wt%), monazite (5.31wt%), and fluorite (23.52wt%). The study also examined the impact of mineral liberation and gangue mineral intergrowth on flotation performance. Flotation tests achieved a rare-earth oxide (REO) grade of 74.12wt% with a recovery of 34.17% in open-circuit flotation, whereas closed-circuit flotation resulted in a REO grade of 60.27wt% with a recovery of 73%. Transmission electron microscopy and scanning electron microscopy coupled with energy-dispersive spectroscopy revealed that monazite remained stable during the HMPT process, while bastnaesite was transformed into Ce7O12 and CeF3, leading to increased collector consumption. Nonetheless, the HMPT process did not significantly affect the flotation performance of rare earths. The enrichment of fluorite in the tailings highlighted its further recovery potential. The integration of HMPT with magnetic separation and flotation presents an efficient strategy for recovering rare earths, iron, and fluorite from Bayan Obo ores.
Int. Journal of Mining Science and Technology (采矿与安全工程)•2024•DOI: 10.1016/j.ijmst.2024.12.006
The storage of solid waste in Bayan Obo has resulted in significant resource wastage and environmental concerns. In this study, an efficient process was developed to recover iron and rare earth elements (REEs) from this waste by processes of hydrogen-based mineral phase transformation (HMPT), magnetic separation, and flotation. Under optimal HMPT conditions (525 °C, 12.5 min, and 30% H2 concentration), an iron concentrate with a TFe grade of 64.09% and a recovery of 95.33% was obtained. The magnetic properties of the solid waste were greatly enhanced by HMPT, allowing the effective magnetic separation of iron minerals. Further optimization of the flotation process resulted in a REEs concentrate with a rare earth oxide (REO) grade of 65%–70% and a REEs recovery of 60%–65%. Hematite was reduced to magnetite during HMPT, and bastnaesite was decomposed to REEs oxides and fluorides, and the particle structure was significantly destroyed. However, changes in monazite, fluorite, and barite were minimal.