激光金属沉积Ti-Zr-Ta合金的制备及其冲击释能特性研究

难熔金属型含能结构材料（ESMs）具有良好的力学性能和优异的冲击释能特性，但由于组元熔点高，利用传统的熔炼铸造法难以制备出大尺寸无缺陷铸件。本研究利用等离子旋转电极雾化制粉技术制备出Ti-Zr-Ta难熔合金粉末，结合激光金属沉积（LMD）技术制备了Ti-Zr-Ta难熔金属型ESMs，并对其组织结构、力学性能和冲击释能特性进行研究。结果表明，利用LMD技术可实现Ti-Zr-Ta难熔金属型ESMs的致密化成型，合金致密度达到98.75%，具有良好的力学性能，其准静态抗拉强度达到1202MPa。弹道枪试验结果表明，在1202m/s的冲击速度下，激光金属沉积Ti-Zr-Ta合金在27 L密闭靶箱内可产生0.144 MPa的准静态压力，释能特性优良。     

Creep strain recovery of an in situ spinel-forming refractory castable under loading/unloading compressive creep conditions

Creep strain recovery after unloading has been well studied for metals and certain ceramic composites; however, it has not yet been investigated for ordinary ceramic refractories applied in industrial furnaces. The present study explores the question whether creep strain recovery can be observed in ordinary ceramic refractories to justify its consideration in the design of such refractories and refractory linings. To this end, the dependence of creep strain recovery on different loading conditions was investigated for a high-alumina in situ spinel-forming castable, commonly used as refractory lining of steel ladles in secondary steel metallurgy. Several loading/unloading compressive creep tests were performed at 1300 °C for different loading histories. Creep strain recovery was observed to occur and it was significantly affected by the holding time and degree of unloading. A longer holding time for the loading period was found to increase the internal stress, which is the driving force for creep strain recovery. In addition, the findings indicate that a higher excess of internal stress over external stress after unloading induces higher strain recovery.     

High temperature interactions between K-rich biomass ash and MgO-based refractories

MgO-based refractories are used in lime kilns to withstand the high temperature and chemical environment. Efforts to reduce CO₂ emissions have led to an increased interest to use bio-based fuels as alternatives to traditional fossil sources. The potential for refractory corrosion from a potassium-rich biomass ash was investigated by studying the infiltration of olive pomace ash into magnesia/spinel refractories. Refractory samples were exposed to the ash at up to 1400 °C for 15–60 min in a CO₂–rich atmosphere. Molten ash infiltrated the refractories through pores and grain boundaries to a depth of up to 9.6 mm, which was quantified with a new systematic procedure. The phase KAlO₂ was identified inside the refractories after exposure, indicating an attack of spinel components by potassium. Phases found in the ash residues also indicated the migration of refractory constituents. Thermochemical equilibrium calculations were also used to investigate the ash/refractory chemistry.     

Calibration of cohesive parameters for a castable refractory using 4D tomographic data and realistic crack path from in-situ wedge splitting test

Crack propagation in an alumina castable refractory with mullite-zirconia aggregates was investigated in-situ using a wedge splitting test performed inside a laboratory tomograph. Four-dimensional (i.e., 3D space and time) data from digital volume correlation were used to investigate the influence of a realistic crack path on the simulation of the fracture process. A cohesive law was chosen, since toughening mechanisms were present, and calibrated via finite element model updating. When a straight crack path was assumed instead of the experimental crack path, a 10% higher fracture energy and a 35% higher cohesive strength were calibrated. Although the force alone could be used in the minimized cost function, the kinematic information gives valuable insight into the trustworthiness of the geometrical hypotheses assumed in the finite element model. Such framework can be applied to study nonlinear fracture processes for different materials with complex toughening mechanisms such as crack deflection or branching.     

A new quantitative criterion to determine slag corrosion resistance of refractories for incinerators

Selecting the most suitable refractory lining from various types/grades of products provided by different suppliers for the hazardous waste incineration rotary kiln is not an easy job to reach a 23-month lifetime. Real-life industrial scale test is time-consuming, i.e., only one or two new products can be tested each year or every other year. Crucible test is a fast way to give a first assessment to test the adaptability of a given product to a slag. However, the classic visual observation to determine the slag penetration zone is usually inconclusive when the materials of the same group are tested and can be sometimes misleading. In this study, crucible tests were performed for 10 commercial chromia-corundum bricks from various sources. After examined with detailed analysis with SEM (Scanning Electron Microscopy) and EDS (Energy Dispersive X-Ray Spectroscopy), highly precise quantitative values of corrosion zones width for samples are derived. A non-dimensional number, the Wear ratio, is introduced as a quantitative criterion to characterize the refractory corrosion resistance. By using this Wear ratio, a correlation is found with the chromia concentration. Quantitative results obtained by this criterion are in line with the real-life observations of industrial scale tests.     

Erosion mechanism of the postmortem Al2O3-Ti2O3-Al sliding gate containing novel Al2O3-Ti2O3 raw materials

Al₂O₃-Ti₂O₃-Al sliding gates were prepared from Al₂O₃-Ti₂O₃ raw materials, sintered corundum and aluminum, and used in trials at steel works. The sliding gate with 30 wt% Al₂O₃-Ti₂O₃ added was used on an 80 t ladle for 4 cycles without macrocracks. The postmortem sliding gate can be divided into the permeation layer (0–0.1 mm), transition I layer (0.1–10 mm), transition II layer (10–20 mm) and unchanged layer from the hole working face outward. XRD, SEM and industrial CT were used to analyze the postmortem sliding gate. The results show that, in the Al₂O₃-Ti₂O₃-Al sliding gate, both Al and Ti₂O₃ are involved in reactions, Ti₂O₃ transforms into Ti₂O and TiO in the transition I layer, and part of the Ti₂O₃ in the transition II layer transforms into Ti₈O₁₅. Titanium compounds with different densities are dispersed in the matrix and form microcracks to improve the thermal shock resistance of the sliding gate, which improved the performance.     

Fabrication and thermal shock behavior of periclase-forsterite aggregates with micro-nanometer dual-pore-size structures

To improve the service life of periclase-forsterite refractories, it is important to develop aggregates with high thermal shock resistance. In this study, periclase-forsterite aggregates with good resistance to thermal shock and micro-nanopores were prepared using high-silicon magnesite, silica, and silica sol. Microcracks were generated in the multiphase aggregates, which inhibited the continuous propagation of cracks during thermal shock through mismatched thermal expansion coefficients. Based on Hasselman's thermal shock stability factor, the reduction in the average thermal expansion coefficient and improved mechanical characteristics were critical factors in improving the thermal shock resistance of the multiphase aggregates. As a binder, silica sol provided nano-SiO₂ and superplasticity, which facilitated the formation of micro-nanopores and strengthened the combination of the various phases in the aggregates.     

Novel Ti2O3–Al2O3 raw materials with controllable Ti2O3 content from the aluminothermic reduction of ilmenite

Titanium-containing refractories have excellent performance, but the high cost limits their application. A series of Ti₂O₃–Al₂O₃ raw materials with different Ti₂O₃ contents were prepared by aluminothermic reduction of ilmenite, while the generated ferrotitanium alloy can be used as raw materials for special steels. Regulating the amount of aluminum added in the system regulates the degree of titanium reduction, and the formed ferrotitanium alloy can achieve separation from the oxides. With decreasing aluminum content of, the Ti₂O₃ content increased, and the continuous distribution of the corundum area decreased, resulting in a continuously distributed Ti₂O₃ area. Our results indicated that the molar ratio of aluminum to ilmenite should be higher than 1.4 to achieve slag iron separation. The reaction model for the aluminothermic reduction was established, and the formation mechanism of Al₂O₃ and Ti₂O₃ in the system was discussed.