The processing of mine solid waste into backfill materials for filling mining areas is one of the key methods of green mining. The deformation and failure patterns of the solid waste cemented backfill during the extraction of mine pillars directly affect the stability of the mining area. Through triaxial unloading confining pressure tests, the mechanical properties and macroscopic failure characteristics of magnesium slag-based (MS-based) backfill were systematically investigated under different MS contents (0%, 20%, 30%, and 40%) and initial confining pressures (0.5 MPa and 2.0 MPa). The evolution laws of deformation parameters of the backfill with confining pressure during unloading confining pressure were explored, and the influences of MS content on deformation parameters of the backfill under unloading confining pressure were discussed. The results showed that during unloading confining pressure, the deformation modulus gradually decreased with decreasing confining pressure and dropped sharply at failure, exhibiting a non-linear relationship with volumetric strain. Conversely, the generalized Poisson's ratio gradually decreased with decreasing confining pressure and increased sharply at failure. The peak deviatoric stress of the backfill first increased and then decreased with increasing MS content. Under an initial confining pressure of 2.0 MPa, when the MS content was 30%, the peak deviatoric stress of the MS-based backfill reached a maximum value of 16.329 MPa, which was 129.82% higher than that at 0% MS content. When the MS content was 0%, 20%, and 30%, the peak deviatoric stress and elastic modulus of the backfill under 2.0 MPa confining pressure were both higher than those under 0.5 MPa confining pressure. Under unloading confining pressure conditions, the MS-based backfill did not exhibit large-scale fracturing or crushing, with only cracks appearing on the surface. A higher initial confining pressure can effectively inhibit the propagation of cracks and failure within the backfill, thereby enhancing its structural integrity and stability. This study provides a reference for the mixing ratio optimization and stability analysis of the MS-based backfill materials in mining engineering.

To investigate the multiphase flow (oxygen-steel-slag-argon) and splashing phenomena within a 210-ton converter operated under top-bottom combined blowing conditions, a three-dimensional numerical simulation model was established. This simulation integrated the Realizable k-epsilon model, the volume of fluid model, and the discrete phase model. The molten steel was not exposed to the oxygen when the top-blown oxygen flow rate was 40 000 m3/h, and the oxygen jet directly contacted the molten steel at top-blown gas flow rates of 44 000 and 48 000 m3/h. The maximum jet speed increased from 17.21 to 163.04 m/s as the top-blown gas flow rate increased from 40 000 to 48 000 m3/h. Meanwhile, the deflection angle of the oxygen jet first increased and then decreased. A positive correlation was observed between the jet speed and the blowing number. The maximum blowing number increased from 0.52 to 19.82 as the oxygen jet flow rate increased from 40 000 to 48 000 m3/h. The empirical formula for cavity depth containing two layers of fluid was obtained.

To promote the further application of the new magnesium slag-based complete solid waste backfill material (MFG-CTB), this paper studies the effects of curing temperature and age on the mechanical properties, deformation characteristics, and pore structure characteristics of MFG-CTB through methods such as uniaxial compression tests, MIP, and SEM. On this basis, a correlation analysis between the pore structure and compressive strength was conducted, and a strength prediction model for MFG-CTB was constructed. The results show that increasing the curing temperature can effectively improve the compressive strength of MFG-CTB at different ages, and the improvement range first increases and then decreases with the increase of curing temperature. However, it will prolong the closure time of pores and cracks in MFG-CTB, weaken its plastic deformation capacity, and the post-peak bearing capacity first increases and then decreases with the rise in temperature. The pore structure characteristics of MFG-CTB generally show refined pore size and increased structural complexity with the increase of curing temperature, which is beneficial to the improvement of the strength of the backfill, and this is also verified in the quantitative analysis of the pore structure. However, when the curing temperature exceeds 35 °C, the improvement effect on the pore structure of MFG-CTB is not apparent. The compressive strength of MFG-CTB is negatively correlated with pore characteristic parameters and positively correlated with the pore fractal dimension, among which the average pore size, capillary pore fractal dimension, and gel pore volume have the highest correlation with compressive strength. The MFG-CTB compressive strength prediction model established based on this has a better prediction effect than traditional models.

Utilizing solid waste resources and lowering backfill costs are made possible by the preparation of cementitious materials as cement substitutes using magnesium slag (MS) and blast furnace slag (BFS). Uniaxial compression tests were carried out on MS-BFS-based backfill with different MS contents (20

The three-dimensional multiphase flow and the unreacted core desulfurization kinetic model were coupled to predict the sulfur content in hot metal during the Kanbara reactor (KR) stirring process. The effect of the impeller rotation speed, initial sulfur content, desulfurizer diameter, and desulfurizer addition on the variation of the sulfur content and desulfurization rate was revealed. The accuracy of the current model was validated through industrial trials involving sampling and measurement of the sulfur content in hot metal. Results indicated that the speed of the hot metal and the vortex distribution were primary factors determining the dispersion degree of the desulfurizer and the desulfurization rate. The variation of the average sulfur content during the KR process essentially followed an exponential distribution. The desulfurization rate constant increased with the higher rotation speed, higher desulfurizer addition, and lower desulfurizer diameter. However, the initial sulfur content in the hot metal hardly affects the desulfurization rate constant. A formula for predicting the variation of the sulfur content with the initial sulfur content, impeller rotation speed, desulfurizer diameter, total mass of desulfurizers, total mass of hot metal, and desulfurization time was proposed to provide theoretical guidance for the actual production.

The microscopic pore structure characteristics are of significant importance to the strength properties and engineering applications of magnesium slag-based backfill (MSB). The pore size distribution, porosity, specific surface area, and pore fractal characteristics of MSB were investigated using mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). Concurrently, SEM images were quantitatively processed to analyse various pore parameters within specific regions of the MSB. The results indicate that the cumulative mercury intrusion curve of MSB exhibits three stages: slow growth, rapid growth, and high-pressure rapid growth. With increasing curing age, the pore size distribution of MSB gradually concentrates around the dominant pore diameter range (10-100 nm), and the overall pore diameter decreases. As curing age increases, the MIP-derived porosity and specific surface area of MSB initially decrease and subsequently increase. Quantitative SEM analysis reveals that the pore probability entropy exceeds 0.95, the pore fractal dimension ranges from 1.17 to 1.25, and the average form factor ranges from 0.31 to 0.37. At the micropore scale (<10 nm) and minipore scale (10-100 nm), the backfill strength exhibits a significant positive correlation with the pore volume percentage. The SEM-derived porosity of MSB exhibits a significant negative linear correlation with compressive strength.

Segregation-induced banding is known to degrade the impact toughness of steels, yet the fracture stage most affected by such heterogeneity and the underlying microstructural origin remain unclear. In this work, normal and segregated specimens of a high-strength bainitic rail steel were compared to clarify how segregation-induced martensitic bands control impact fracture. Instrumented Charpy testing was used to resolve the impact energy into different fracture stages, while pre- and post-impact microstructural characterization was used to compare the microstructural features of the martensitic band and the bainitic matrix and to identify microstructural evolution upon impact. The results show that segregation-induced toughness loss is stage-selective, with the most pronounced degradation occurring during stable crack propagation. The decisive microstructural feature responsible for this stage-selective loss is the boundary network: the martensitic band contains higher densities of most hierarchical boundary categories, which would conventionally imply improved crack resistance, but a markedly lower density of high-{110}-specific misorientation angle boundaries than the bainitic matrix. This unfavorable boundary network is proposed to increase the effective spacing between barriers to dislocation slip transfer, promote localized dislocation pile-up and stress concentration, and thereby reduce resistance to stable crack propagation.

In the current study, a three-dimensional mathematical model was established for the vacuum suction casting process of the high-temperature molten metal. The volume of fluid (VOF) multiphase model, the k-ε turbulent model, and the enthalpy-porosity solidification model were coupled to systematically investigate the transient multiphase flow, heat transfer, and solidification of the high-temperature molten metal during suction casting. The precise control of the negative pressure in the ingot mold was achieved through a user defined function (UDF). The current mathematical model was validated by industrial trial results, showing that the predicted final product mass in the ingot mold was 46.04 kg, with a relative deviation of 6.7 pct from the trial value, and the solidification morphology exhibited good agreement. The suction casting temperature, the vacuum degree inside the ingot mold, and the inner diameter of the suction pipe were key parameters affecting the filling efficiency. Increasing the system vacuum degree or enlarging the inner diameter of the suction pipe can enhance the jet flow rate at the suction pipe outlet, shorten the duration of negative pressure, improve the mold filling ratio, and reduce the residual metal mass in the upper chamber. When the filling time of the upper chamber ranged from 11 to 27 seconds, it exhibited a negative correlation with the final product mass in the ingot mold, with a fitted equation expressed as Q = −0.026 t2 + 0.208 t + 51.24, where Q is the mass of the metal in the mold chamber in kg and t is the time required for filling the upper chamber in seconds. When the filling time was less than 14 seconds or greater than 24 seconds, the residual mass of metal in the upper chamber stabilized at approximately 17.5 and 24.0 kg, respectively. This study provided a theoretical basis and quantitative guidance for optimizing the vacuum suction casting process of high-temperature molten metals.

In the current study, a three-dimensional multi-physics model was developed to systematically investigate the effects of the roll-type electromagnetic stirring (EMS) on the transient flow, solidification, and inclusion transport during the slab continuous casting (CC) process. In the model, the large eddy simulation (LES) was employed to describe the turbulence flow, the discrete phase model (DPM) was used to calculate the trajectory of inclusions, the enthalpy-porosity method was adopted to simulate solidification, and an electromagnetic force source term was incorporated. The distribution of the magnetic field and inclusions was validated through industrial trials. The effect of casting speeds of 0.7, 0.9, and 1.1 m min−1 was investigated. With increasing casting speeds, the liquid pool depth was expanded, resulting in an enhancement of the electromagnetic force acting region on the molten steel. Furthermore, an asymmetric distribution of entrapped inclusions across the cross section was induced by the roll-type EMS, with high probability regions mainly concentrated in the subsurface layer and the EMS-induced impact zone of solidification front. Meanwhile, the intensified flow within the liquid pool caused the peak probability of inclusion entrapment in the impact zone of solidification front to shift toward the narrow face, accompanied by a remarkable increase in its magnitude. Through the present study, the key physical mechanism governing the distribution of inclusions under the action of roll-type electromagnetic stirring was clarified, and a quantitative basis was provided for the precise control of slab cleanliness through the collaborative optimization of EMS parameters and casting speed.

A three-dimensional numerical model was established based on a 210 t industrial ladle to simulate the multiphase flow behavior during the entire teeming process. The volume of fluid method was used to capture the gas-slag-steel interface, and large eddy simulation was employed to resolve the turbulent flow. A discrete phase model was applied to simulate the entrainment of dispersed inclusions, and the simulation results were validated by industrial sampling under different retained steel conditions. In addition, a user-defined function was developed to calculate the slag detection system, and the predicted critical slag carryover moments matched well with online recorded results. Parametric studies showed that with the increase of the interfacial tension from 0.4 to 1.8 N/m the critical steel mass was decreased by 3.53 t, while increasing the slag viscosity from 0.1 to 0.6 Pa s resulted in a gain of 0.57 t. The clogging layer around the ladle nozzle significantly advanced the slag carryover. A 100 mm clogging layer increased the retained steel by 3.89 t. Relative influence weights of the interfacial tension, slag viscosity, and clogging layer height were calculated to be 44.2%, 7.1%, and 48.7%, respectively. Industrial trials confirmed that retaining 25 t of steel reduced 40% of the slag-type inclusions, comparing to the condition without the retained steel.

This study investigates the influence of Ag and processing routes on the evolution of Portevin-Le Chatelier (PLC) behavior of 5xxx aluminum alloys. Results indicate that the modified alloy, enhanced with the alloying element Ag, can suppress the serrated yielding behavior and increase the strength by approximately 80 MPa during aging treatment. Ag atoms promote stable Mg-Ag cluster and reduce solute Mg atoms in the matrix, which weakens the pinning effect on dislocations. Furthermore, compared to the T6 process, the critical strain of the T8 process alloy reaches a maximum of about 12 %. The serrated flow propagation characteristics gradually transition from continuous propagation to a combination of continuous and spatial jumping propagation. This behavior results from pre-deformation prior to aging, which facilitates the formation of additional substructures and forest dislocations that are uniformly distributed during the subsequent aging recovery process.

In the current study, a novel dimensionless slag entrainment number, Zc, combining the effects of the geometry of the continuous casting (CC) mold and nozzle, operating parameters, physical properties of the steel and slag, and turbulent flow, was proposed to predict slag entrainment during the CC process. The accuracy and applicability of the slag entrainment prediction using the dimensionless slag entrainment number Zc have been successfully validated by numerical simulations.

Bioleaching is confronted with problems, such as low efficiency, long production cycle length, and vegetation destruction. In order to solve problems above, fly ash and low-grade copper sulfide ores were used to investigate bioleaching behaviors and bacterial community succession. Results showed that copper recovery, bacterial concentration, total proportion of main leaching bacteria including Acidithiobacillus ferrooxidans, Acidibacillus ferrooxidans, and Leptospirillum ferriphilum, were improved through using appropriate dosage of fly ash. The maximum copper recovery of 79.87

The mechanical performance of Fe-TiB2 composites produced via conventional methods is limited by inadequate microstructure refinement, thereby restricting their application in high modulus steels (HMSs). To overcome this, we proposed a novel strategy integrating high energy laser-assisted prealloying and rapid in situ TiB2 precipitation to fabricate nanostructured Fe-5vol.%TiB2 (equivalent to Fe-2.4 wt%TiB2) composites via laser powder bed fusion (LPBF) from a predesigned Fe-Ti-TiB2 powder mixture. The optimized process yields a bulk sample with a remarkably refined microstructure characterized by in situ nano TiB2 nanoparticles (20-150 nm) uniformly dispersed within a nearly equiaxed, texture-free alpha-Fe matrix with grain sizes less than 500 nm-an order of magnitude smaller than the matrix grains typically achieved in other additively manufactured particle-reinforced metal matrix composites. This microstructural refinement results in superior mechanical properties, with a Vickers hardness of similar to 482.5 HV, a yield strength of similar to 1027 MPa, and a Young's modulus of similar to 239.8 GPa. Notably, the yield strength is similar to 190% higher than that of Fe-20 vol% TiB2 composites produced via conventional methods, and the specific Young's modulus (similar to 32 GPa cm(3)/g) is similar to 23% greater than that of established metallic structural materials (similar to 26 GPa cm(3)/g). The significant grain refinement is attributed to the synergy of the solutes and in situ-formed TiB2 nucleant, providing sustained heterogeneous nucleation in the Fe-Ti-B melt during solidification. Additionally, uniform nano TiB2 particle distribution is achieved by the interaction between the recoil pressure and Marangoni convection, which thoroughly stirs the molten pool and prevents particle agglomeration.

In the current study, a comprehensive kinetic model was developed to predict the desulfurization of the molten steel during RH steel refining process, coupling the three-dimensional fluid flow. A user-defined scalar Eulerian-Eulerian model was used for this purpose, through which desulfurizer particles was considered a continuous phase so that the concentration of desulfurizer particles was calculated in the steel flow field. The desulfurization simulation was achieved through the interaction user-defined function between the desulfurizer phase and the molten steel phase, which was related to the size, the sulfur capacity and the mass transfer coefficient of desulfurizer particles. The model was validated by actual industrial trial data. The motion of desulfurizer particles with a 0.1 mm diameter was influenced by eddy currents and they moved toward the down-leg side and accumulated on the right side of the ladle. Larger particles with a 30 mm diameter remained at the surface of vacuum chamber due to their big buoyancy. Smaller particles had a larger desulfurization efficiency due to their bigger contact area with the molten steel, showing a rapid decrease of the sulfur content while a quick sulfur saturation due to their small volume. Larger particles maintained a longer desulfurization duration due to their bigger volume and big sulfur capacity as well. With a same injection rate, the total desulfurizer amount only influenced the final sulfur content and hardly influence the average desulfurization rate during the desulfurizer injection. The average desulfurization rate was influenced by the injection rate. The maximum desulfurization rate of 0.093 ppm/s was obtained with a 150 kg/min flow rate of the desulfurizer injection. Lowering lance position improved desulfurization efficiency and reduced final sulfur content as well. A regression formula was derived to quantitatively describe the effects of the size, the injection amount, the injection flow rate of desulfurizer particles, and lance position on the desulfurization rate, which can be used to predict sulfur variations in the molten steel during RH refining process.

In the current study, effects of a carbon-bonded magnesia (MgO  C) refractory and a magnesia (MgO) refractory on the cleanliness of a high-carbon Al-killed steel and on the degree of refractory are investigated using laboratory experiments, thermodynamic calculation, and a kinetic modeling. The refractory/steel interface layer and inclusions in the steel are analyzed. After a 90 min contact between the refractory rod and the steel, the penetration of the molten steel into MgO refractory is small. An about 0.1 mm thick interface layer containing CaO–Al 2 O 3 –SiO 2 –MgO is generated at the boundary of magnesite particles while the composition of inclusions in the steel changes very little. The molten steel penetrated 1 mm into MgO  C refractory through grain boundaries, forming channels due to the graphite consumption. A new 20 μm thick interface layer containing CaS and MgO is formed between the steel and MgO  C refractory. The formation of CaS is favored at the steel/MgO  C refractory and is rarely existed at the steel/MgO refractory during cooling process. The average content of MgO in inclusions increases from 6.22 to 30.05 wt% while the Al 2 O 3 content in inclusions decreases from 84.57 to 69.95 wt% reacting for 90 min.

Herein, a coupled three-dimensional large eddy simulation model and volume of fluid model is established to systematically investigate the effect of the argon injection through single-channel and multi-channel stopper rods, casting speed, and argon flow rate on the molten steel flow, spatial distribution of bubbles, and jet characteristics of a bifurcated submerged entry nozzle (SEN). The comparison with the water model shows that the current model can accurately predict the bubble distribution in the SEN. The multi-channel argon blowing makes the argon distribution more uniform and generates bubbles with smaller diameters and larger quantities. The average diameter of bubbles is 16.72 mm in the single-channel blowing, while the average diameter of bubbles is 12.03 mm in the multi-channel blowing. The dispersion degree of argon bubbles increases with the increase of casting speed. The jet speed and backflow speed increase with the increase of the casting speed, while the jet vertical angle and the proportion of the backflow zone decrease gradually. With the increase of the argon flow rate, the fluctuation of the backflow speed at the outport will also increase. The injection of argon has a significant impact on the jet characteristics at the outport.

A three-dimensional (3D) mathematical model was established, coupling the large eddy simulation (LES) turbulence model, heat transfer model, solidification model, discrete phase model (DPM), and dynamic mesh model. Based on the actual continuous casting (CC) end process, the numerical simulation was divided into 4 stages. A method for calculating the motion velocity of the dynamic wall and the solidified shell was proposed to achieve the coupled simulation of transient flow, heat transfer, and solidification. In stage 1, molten steel speed and jet depth decreased as casting speed reduced, while the shell thickness steadily increased. In stage 2, after the submerged entry nozzle (SEN) removal, the molten steel speed and temperature dropped rapidly, and the circulation flow dissipated. In stage 3, the remaining molten steel region gradually decreased, and complete solidification occurred at approximately 4 647.5 s, with the final solidification position located about 0.28 m below the end of the last slab. Based on the actual CC end stages and the entrapped positions of inclusions, a method for calculating the actual positions of inclusions was introduced to predict the 3D spatial distribution of inclusions in a CC end slab. The normalized number (NN) of inclusions exhibited a fluctuating downward trend with the increasing distance below the end of the last slab. It was recommended to cut the last slab at 4 m to ensure cleanliness, while the 3D normalized number density (NND) of inclusions in regions beyond 7 m below the end of the last slab reached a lower stable value.

Sandstone-type uranium deposits have complex pore structures that act as conduits for leaching solutions during in-situ leaching (ISL), and their geometry strongly influences fluid transport and leaching performance. Key parameters such as porosity, pore size distribution, and pore connectivity determine lixiviant migration paths and reaction interfaces. Accurate characterization of these parameters, followed by three-dimensional (3D) reconstruction and numerical simulation of fluid flow, is essential for improving ISL efficiency. In this study, micro-computed tomography (micro-CT) was combined with software platforms including Avizo, Dragonfly, and COMSOL to establish a workflow for quantitative pore structure analysis, multi-scale pore identification, and flow simulation. Quantitative characterization yielded a total porosity of 16.20

In this work, we demonstrate a phase engineering strategy, based on a composite design of monomorphic diamond (MD) reinforced FV520B maraging steel, for controlling matrix phase constituents with high strength and ductility. Benefiting from the enhanced grain growth rate induced by the MD addition, the solidification structure transition from planar to cellular and further to dendritic was achieved. The dissolved MD solute modifies the martensite-to-austenite transformation kinetics, promoting the stabilisation of a predominantly austenitic phase structure. Meanwhile, the elemental segregation around the cellular structure contributes to the massive formation of the M23C6 carbides. Consequently, the microstructural changes due to the MD particle addition result in an exceptional synergy of strength and ductility. This work provides a promising way to fabricate dispersion-strengthened maraging steels with high overall performance.