钢铁研究学报(英文版)
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2024 Vol. 31 No. 3
Published: 2024-03-25
Original Paper
531
Jing-feng Wang, Lin-zhu Wang, Chao-yi Chen, Xiang Wang, Fei Zhao
Effect of rare earth on primary carbides in H13 die steel and their addition method: a review
Hot!
Larger-sized primary carbides lead to stress concentration during the application of H13 hot-work die steel, resulting in microcracks and fatigue failure. Rare earth was usually added to modify the carbides and inclusions. The existing literature is reviewed on the effect of rare earth on primary carbides in H13 steel. A comprehensive review on the effect of rare earth on the characteristics of primary carbides, i.e., number, size, morphology, and thermal stability inH13 steel, was done. The precipitation mechanism and nucleation of primary carbides with rare earth were summarized. The position and form of rare earth in steel and their effects on alloying elements segregation were reviewed. The addition techniques of rare earth in H13 steel were compared, and the prospects for other uncommon rare earth and emerging technology were present. Based on the current references, it can be known that adding rare earth facilitated refined and dispersed primary carbides. The size of primary carbides would be reduced, and their morphology would be improved because the rare earth inclusions formed in H13 steel can act as nucleation cores for γ- Fe or δ-Fe, refining the dendritic structure. Besides, the number of primary carbides at grain boundaries would be significantly reduced. However, rare earth had little impact on thermal stability. The nucleation of primary carbides tended to be inhibited due to themodification of inclusions by rare earth which were likely to be nucleation cores for primary carbides. Rare earth had been reported to affect themechanism and process of primary carbide precipitation. Additionally, the addition of rare earth can inhibit the segregation of alloying elements and carbon diffusion by calculation. Thus, laboratory experiments and theoretical calculations need to be conducted to study the states and evolution of rare earth steels.
2024 Vol. 31 (3): 531-551 [
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Original Paper
552
Fang-lei Dai, Xiao-hui Fan, Xiao-xian Huang, Xu-ling Chen, Min Gan, Zhi-yun Ji, Zeng-qing Sun
Prediction of suitable water content in granulation of sintering mixture based on Litster’s model
Suitable water content plays a decisive role in the granulation of sintering mixtures. Herein, a method was proposed to predict the suitable water content for effective granulation on the basis of Litster’s granulation model. The granulation effectiveness of a sintering mixture was predicted by the model, with the allowance error of ± 10%. The effects of the water absorption properties, particle size composition and content of adhesive particles on the suitable water content were studied. The results showed that the allowable error of prediction was within ± 0.5% compared to the experimentally determined suitable water content. With an increase in adhesive powder content of mixtures with higher water absorption, the suitable water content increased to achieve similar granulation effectiveness. Moreover, as the amount of concentrates increased, the suitable water content first increased and then remained steady. The influence of the water absorption characteristics of the adhesive particles on the suitable water content was less than that of their particle size composition in the mixture.
2024 Vol. 31 (3): 552-560 [
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561
Yao-zu Wang, Jian-liang Zhang, Qiang Cheng, Hui-qing Jiang, Zheng-jian Liu, Yu-bo Tan
Interface interaction between SiO2 and magnetite under high temperature: particle migration and inhibition mechanism
Silicon is one of the main gangue components in iron ore, usually in the form of quartz and olivine. Numerous studies have shown that SiO
2
has a two-sided effect on the consolidation of pellets during high-temperature oxidation roasting of magnetite. However, it is very difficult to capture the structural evolution and migration mechanisms during high-temperature roasting process by existing experimental methods. Therefore, the influence of SiO
2
on the consolidation behavior of magnetite was studied through a series of roasting experiments and molecular dynamic simulation. The results show that the consolidation index and particle growth index decrease with the increase in SiO
2
content in the particles. At 1573 K, the liquid phase promotes the recrystallization growth of hematite at high temperature. Molecular dynamic study shows that it is difficult for quartz SiO
2
to form sintering neck with Fe
2
O
3
. When the calcination temperature is higher than 1400 K, the Fe
2
O
3
–Fe
2
SiO
4
system produces a considerable sintering neck structure after relaxation. The atomic migration ability of Fe
2
SiO
4
is much higher than that of Fe
2
O
3
. The higher atomic migration ability of Fe
2
SiO
4
is the main reason for the formation of the sintering neck.
2024 Vol. 31 (3): 561-572 [
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573
Xiao-jie Liu, Yu-jie Zhang, Xin Li, Zhi-feng Zhang, Hong-yang Li, Ran Liu, Shu-jun Chen
Prediction for permeability index of blast furnace based on VMD–PSO–BP model
The permeability index is one of the important production indicators to monitor the operation of blast furnace. It is crucial to grasp the trends of changes in the new permeability index in time. For the complex vibration spectrum of the permeability index, a prediction model of the permeability index based on the VMD–PSO–BP (variational mode decomposition–particle swarm optimization–back propagation) method was proposed. Firstly, the key factors that affect the permeability index of blast furnace were studied from multiple perspectives. Then, the permeability index was divided into multiple sub-modes based on the difference of frequency bands by the VMD algorithm, and a PSO–BP prediction model was established for each sub-mode. Finally, the prediction results of each sub-mode were summed to obtain the final one. The results show that the composite prediction accuracy by using the VMD algorithm is 3% higher than that of the traditional prediction method, which has better applicability.
2024 Vol. 31 (3): 573-583 [
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584
Gang Wang, Jun Xu, Kun He, Zhong-ping Zou, Hao Bai
Heat distribution model under hydrogen-rich low-carbon conditions in blast furnace
Low carbon development of blast furnaces is one of the key technological directions in the current development of ironmaking. Owing to the differences in the physical and chemical properties of hydrogen and carbon, hydrogen-rich media entering a blast furnace will change the heat distribution, thus affecting the stability of production. Accordingly, a heat distribution model was proposed to study the temperature distribution in a blast furnace, simultaneously considering gas–solid heat exchange, slag and iron melting, and chemical reactions. The model was used to analyze the temperature distribution of a 2300 m
3
blast furnace and was verified via comparison with actual production data. Subsequently, the effects of the injection rate of hydrogen-rich media, H
2
concentration, and oxygen enrichment rate of the blast on the temperature distribution were investigated. Results indicated that the increase in the injection rate of the hydrogen-rich media decreased the amount of direct reduction and led to an increase in the furnace temperature. Furthermore, an increase in the oxygen enrichment rate led to a decrease in the furnace temperature, but could reduce the solid fuel ratio, while the change in H
2
concentration had less effect on the temperature distribution. The combination of hydrogen-rich media injection and the increase in the oxygen enrichment rate would help to adjust the temperature distribution to the same level as the conventional blast furnace conditions.
2024 Vol. 31 (3): 584-594 [
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595
Xin-yu Cai, Hao-jian Duan, Ding-han Li, An-jun Xu, Li-feng Zhang
Water modeling on fluid flow and mixing phenomena in a BOF steelmaking converter
A 1:8 physical water model was constructed to investigate the fluid flow and mixing phenomena in the basic oxygen furnace (BOF) converter. The particle image velocimetry was employed to measure the velocity distribution of the bath and the high-speed camera was applied to capture the cavity shape in the combined blowing BOF converter. The mixing time for varied operating conditions was measured by the stimulus-response approach. The cavity depth increased with the decrease in the lance height and the increase in the top gas flow rate while the bottom blowing gas had little influence on the cavity depth. The minimum cavity depth was obtained under the condition of a 69.8 m
3
/h top gas flow rate, a 287.5 mm lance height and a 0.93 m
3
/h bottom blowing gas flow rate, which was 161.2 mm. The mixing time decreased as the lance height decreased and the top blowing gas flow rate increased. The mixing time was first decreased and then increased with the increase in the bottom gas flow rate. With the condition of 69.8 m
3
/h gas flow rate of top blowing, the 287.5 mm lance height and the 0.93 m
3
/h gas flow rate of bottom blowing, the mixing time in the converter was 48.65 s. The empirical formula between the stirring power and the mixing time in the converter was calculated.
2024 Vol. 31 (3): 595-607 [
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608
Zhe Wang, Qi-long Wei, Cheng-bin Shi, Zhan-cheng Guo
Effect of Al2O3/SiO2 mass ratio and CaO content on viscosity and structure of slag for pyrometallurgical processing of spent automotive catalysts
The effect of Al
2
O
3
/SiO
2
mass ratio and CaO content on the viscosity and structure of the CaO–Al
2
O
3
–SiO
2
–6MgO– 1.5ZrO
2
–1.5CeO
2
slag was investigated. The results show that with the increase in Al
2
O
3
/SiO
2
mass ratio, the viscous flow units within the slag gradually change from Si–O–Si to Al–O–Al and Al–O–Si. Furthermore, the substitution of Al
2
O
3
for SiO
2
leads to the transformation of Si–O bonds towards weaker Al–O bonds, which weaken the bond strength of the aluminosilicate networks, thus leading to a decrease in the viscosity of slag. The increase in CaO content effectively promotes the depolymerization of the aluminosilicate networks, resulting in a significant decrease in the viscosity of the slag. The slag with Al
2
O
3
/SiO
2
of 0.7–1.5 and CaO of 30 wt.% shows promise as the reference slag system for the Fe-collection smelting of spent automotive catalysts due to its good comprehensive performance.
2024 Vol. 31 (3): 608-621 [
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5
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622
Pu Wang, Liang Chen, Qun-wei Tang, Wei-tao Li, Shao-xiang Li, Jia-quan Zhang
Propagation form of internal cracks induced by continuous casting soft reduction and control strategy for internal quality
The propagation form of internal cracks induced by continuous casting soft reduction and the control strategy for enhancing the internal quality of 45 steel through industrial trials and a three-dimensional flow–heat transfer–solidification coupling model were investigated. The results showed that the internal cracks induced by soft reduction exhibited a characteristic of being ‘‘coarse in the middle and fine at both ends’’, and displayed an elliptical arc distribution on the loose side of the strand cross section. The cracks originated within the brittle temperature range and propagated inward to the liquid impenetrable temperature and outward to the zero ductility temperature or below. The control strategy for enhancing the internal quality of the 45 steel strand through soft reduction is to adjust the casting speed or the reduction zone appropriately, ensuring that the central solid fraction of the reduction zone falls within the range of 0.33–0.99. At this point, a reasonable reduction amount is allocated to eliminate the center shrinkage cavities and center segregation, even if it results in minor reduction-induced cracks.
2024 Vol. 31 (3): 622-633 [
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634
Yi Wang, Jian Yang, Bao Wang, Hai-jun Zhang, Juan Han, Pei-yan Pei, Wen-long Lv, Jian-an Zhou
Permanent lining castable with low bulk density and thermal conductivity: bauxite castable for tundish obtained by adding pearlescent sand
The low thermal conductivity and light mass of castables for tundish permanent linings are crucial for minimizing the heat loss of molten steel. In consideration of the low bulk density and thermal conductivity of pearlescent sand, the thermal insulation performance of castables was attempted to be improved by adding pearlescent sand. Pearlescent sand was modified to prevent the strength of its porous structure from deteriorating. The modification mechanism of pearlescent sand and the effect of pearlescent sand on the performance of bauxite castables were studied. The results suggested that the addition of the modified pearlescent sand significantly raised the apparent porosity and decreased the bulk density of bauxite castable. At 1000 °C, the bulk density of more than 60% of the modified pearlescent sand–bauxite castable was only 2.03 g/cm
3
. The mechanical properties and thermal shock resistance of the modified pearlescent sand–bauxite castable were inferior to those of conventional bauxite castable but were adequate to meet the use conditions of castables for tundish permanent linings. At high temperatures of 200–800 °C, the thermal conductivity of more than 60% of the modified pearlescent sand–bauxite castable was smaller than that of conventional bauxite castable. The addition of the modified pearlescent sand can greatly reduce the thermal conductivity and bulk density of bauxite castable.
2024 Vol. 31 (3): 634-646 [
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647
Shun-hu Zhang, Yi Zhang, Wen-hao Tian, Yan Li
An analytical model of hot rolling force for a thick plate by combining globally optimal approximation yield criterion and egg-circular velocity field
For the sake of solving the problem that it is difficult to be integrated for the Mises specific plastic power due to its nonlinearity, a new linear criterion, named the globally optimal approximation criterion, is constructed by the polygonal approximation to the Mises circle. The new criterion is proved to be the linear function of the principal stress components
σ
1
,
σ
2
and
σ
3
and the trajectory of it on the p-plane is a non-equiangular but equilateral dodecagon intersecting the Mises circle. The theoretical results of the current criterion described by the Lode stress parameters are in excellent accordance with the experimental results. Meanwhile, according to the trend that the metallic flow velocity between rollers aggrandizes gradually from the inlet to the outlet during the hot rolling of a thick plate, a biomimetic velocity field is proposed in which the horizontal velocity component fits the egg-circular curve distribution. The velocity field and its simulated results agree quite well. Subsequently, using the determined linear criterion, energy analysis of the constructed velocity field is utilized to obtain the interior deformation power, while the vector decomposition approach is utilized to obtain the frictional power and shear power. On this basis, the overall power is obtained and the analytical solutions are generated for the rolling torque, rolling force and the coefficient of the stress state under different egg curves by minimizing the neutral angle. Furthermore, the parameter optimization of the characteristic parameter
ρ
which affects the slope of the egg-circular curve is carried out and the best egg-circular curve which can minimize the energy consumption is determined. The best agreement between the theoretical and observed values of rolling force and rolling torque is under this curve, and the mean relative errors of the rolling torque and rolling force are no more than 2.93%, while the maximum error is no more than 8.35%.
2024 Vol. 31 (3): 647-659 [
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660
Shuang Liu, Chen Du, Cong Zhang, Zhen-hua Bai
Anti-saturation fault-tolerant adaptive torsional vibration control with fixed-time prescribed performance for rolling mill main drive system
An anti-saturation fault-tolerant adaptive torsional vibration control method with fixed-time prescribed performance for the rolling mill main drive system (RMMDS) was investigated, which is affected by control input saturation, actuator faults, sensor measurement errors, and parameter perturbations. First, we gave a continuously differentiable saturation function to approximate the control input saturation characteristic of the RMMDS, translating the saturation characteristic into the matched uncertainty and unknown time-varying gain in the system. Then, an RMMDS mathematical model with unmatched uncertainty and unknown time-varying gain was developed, taking into account the presence of control input saturation, actuator faults, sensor measurement errors, and parameter perturbations. Based on the established mathematical model, an error transformation model of the roll speed tracking was constructed by the equivalent error transformation method. According to the error transformation model, a barrier Lyapunov function and a novel adaptive controller were studied to ensure that the roll speed tracking error always evolves inside a fixed-time asymmetric constraint. Finally, numerical simulations were performed in Matlab/Simulink to verify the effectiveness and superiority of the proposed control method in suppressing the RMMDS torsional vibration.
2024 Vol. 31 (3): 660-669 [
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670
Xian-lei Hu, Qin-cheng Xie, Yi Yuan, Ying Zhi
Microstructure and mechanical properties of Ti/Al/Ti clad plates prepared via powder-in-tube method
The Ti/Al/Ti clad plates exhibit a broad spectrum of potential applications. However, the conventional techniques of hotpressing composite and explosive composite are intricate and environmentally hazardous. A novel method was introduced for preparing clad plates, namely, the powder-in-tube method. This method involves a combination of cold rolling, annealing at a temperature of 550 °C, and double rolling. The morphology of the intermetallic compound layer was analyzed through the utilization of interface stripping test, tensile test, and microscopic characterization. The interface morphology, interface bonding properties, tensile fracture structures, and properties of plates under the first and second rolling were compared, along with the effects of intermetallic compounds on the interface properties. The results indicate that the powder-in-tube method, when annealed at 550 °C, can produce a composite plate featuring a complete and uniform Ti/Al interface. The obtained plate exhibits a peeling strength of 21.5 N/mm, tensile strength of 424 MPa, and elongation of 11.5%. Furthermore, a systematic analysis was conducted to determine the causes of performance degradation observed during annealing at temperatures of 600 and 650 °C.
2024 Vol. 31 (3): 670-687 [
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688
Wen-quan Sun, Sheng-yi Yong, Tie-heng Yuan, Ting-song Yang, An-rui He, Chao Liu, Rui-chun Guo
Effect of post rolling stress on phase transformation behavior of microalloyed dual phase steel
The slow phase transformation of microalloyed dual phase steel makes the nonuniform stress and temperature fields during the post rolling cooling process have a significant impact on the phase transformation process. Given the relatively slow phase transformation of DP780 steel within the microalloyed dual phase steel series, the influence of stress on the phase transformation behavior of DP780 steel was investigated. To quantify the nonuniform thermal and stress conditions in the steel coil, a thermo-mechanical coupled finite element model of the hot-rolled strip cooling process was established. Based on the simulation data, DP780 steel was chosen as the research material, and Gleeble 3500 thermal simulation equipment was used for experimental validation. The thermal expansion curves were analyzed through regression to establish the dynamic model of DP780 steel phase transformation under stress. Subsequently, metallographic analysis was conducted to determine phase transformation type and grain size of DP780 steel. The results confirmed that the stress promotes the occurrence of semi-diffusion-type bainite transformation. Furthermore, an appropriate level of stress facilitates the growth of bainitic grains, while the increased stress inhibits the growth of ferritic grains.
2024 Vol. 31 (3): 688-699 [
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700
Xiang-jun Liu, Ji-chun Yang, Hui-ping Ren, Xiao-bin Jia, Ming-yi Zhang, Chang-qiao Yang
Effect of solute Ce, Mn, and Si on mechanical properties of silicon steel: insights from DFT calculations
The influence of solute Ce, Mn, and Si on the mechanical properties of silicon steel was investigated by first-principles calculation. Ce, Mn, and Si can all be solubilized in Fe matrix. Ce significantly reduces the incompressibility and rigidity of the system but also significantly improves the toughness and machinability. The effect of Mn on mechanical properties of the system is not obvious. Si has a significant effect on the improvement in incompressibility and rigidity but a limited effect on the improvement in toughness and machinability. The metallic bond strength of Fe–Ce, Fe–Mn, and Fe–Si doped systems is weaker than that of the pure Fe system, which can be used to explain the reduction in the incompressibility and rigidity of these doped systems. The relatively high electron cloud density in the doped system may be responsible for the increase in toughness.
2024 Vol. 31 (3): 700-709 [
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710
Yan-hui Hou, Ze-kun Xu, Shi-long Zhou, Guang-qiang Li
Atomic-scale mechanism of effect of co-separation of elements at interface of ferrite and austenite on Cr-depleted zone of duplex stainless steel
Three-dimensional atom-probe tomography and first-principles calculation combined with density functional theory were used to study the effect of the co-segregation of different elements formed during the solidification process of S32205 duplex stainless steel on the Cr-depleted zone at the interface between ferrite and austenite. It was found that the cosegregation of different elements formed during the solidification process of duplex stainless steel can also form Crdepleted zone at the interface between ferrite and austenite. Moreover, Mo, Si, B, C and P atoms promote co-segregation with Cr atoms, which promotes the formation of Cr-depleted zone at the interface between ferrite and austenite in duplex stainless steel. Mo and Si strongly promote the segregation of Cr at the interface between ferrite and austenite, thereby promoting the formation of Cr-depleted zone. B, C and P elements also promote the segregation of Cr element at the interface between ferrite and austenite and the formation of Cr-depleted zone, but their effect is weaker than that of Mo and Si elements. These conclusions provide a new theoretical basis for improving the intergranular corrosion performance of duplex stainless steel.
2024 Vol. 31 (3): 710-718 [
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719
Jin-guo Gao, Shu-lei Yang, Shu-feng Yang, Jing-she Li, Wei Liu, Meng-jing Zhao, An-ren Wang
Evolution of inclusions in vacuum induction melting of superalloys containing 70% return material
The variation law of inclusions type and size in the vacuum induction melting process and ingot of Ni-based superalloy containing 70% return material was studied by industrial test sampling, and the mechanism of inclusions formation was analyzed with thermodynamic calculations. The results show that there are mainly two types of composite inclusions in the vacuum induction melting of Ni-based superalloys, which are nitride- and oxide-based composite inclusions, like Al
2
O
3
– SiO
2
–Cr
2
O
3
, TiN–(Mo, Nb)C, etc. The type and proportion of inclusions from the center to the edge of the vacuum induction ingot did not change significantly. The number density of inclusions from the center to the edge of the ingot varied less, and the size of inclusions became smaller from the center to the edge. In addition, thermodynamic calculations show that oxides (M
2
O
3
) are present in the liquid phase and mainly contain Al, Ti, Cr, Fe and O elements. The nitride consists mainly of Ti and N and contains small amounts of Cr, C, Nb, and Mo elements. This is consistent with the results of industrial tests. As the temperature decreases, the precipitation phases such as M
2
O
3
, MN, γ, MC, δ, γ‘ and l phases are gradually precipitated, where oxides and nitrides are present in the liquid phase. The contents of O and N elements are the main influencing factors for the inclusions content and precipitation temperature; when the nitrogen content is reduced to below 0.0015%, it can make MN precipitate below the liquid-phase line.
2024 Vol. 31 (3): 719-728 [
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729
Ya-zhou He, Ya-qing Hou, Peng Shen, Hao Zhang, Dong Zhou, Hang Su
Fabricating functionally graded Fe–Cr–Co permanent magnetic alloys via laser powder bed fusion
Laser powder bed fusion (LPBF) in-situ alloying technology offers the possibility to construct gradient materials with varied structures and properties. Functionally graded Fe–Cr–Co permanent magnetic alloys were fabricated by LPBF and in-situ alloying mixed powders of Fe, Cr, and Co elements. The effects of different Fe, Cr and Co contents on the microstructure, magnetic properties and hardness of Fe–Cr–Co alloys prepared by LPBF were studied. The as-built Fe–Cr– Co alloys present a single body-centered-cubic phase and have a homogeneous distribution of elements. The mechanical properties and magnetic properties of the compositionally graded sample show a gradient variation. With the increase in Cr content, the Vickers hardness of the sample increases, and the saturation magnetization of the sample decreases. The optimal magnetic properties in an isotropic state are given as coercivity
H
cB
= 21.65 kA/m, remanence
B
r
= 0.70 T and energy product (
BH
)max= 5.35 kJ/m
3
, which are comparable to or higher than the reported magnetic properties in an isotropic state prepared by traditional powder metallurgy. LPBF in-situ alloying technology has the potential to further explore Fe–Cr–Co magnetic materials, such as those consisting of multiple or more constituent elements, and to maximize the compositional flexibility of magnetic materials.
2024 Vol. 31 (3): 729-737 [
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738
Qian Dang, Gang Huang, Ye Wang, Chi Zhang, Guo-huai Liu, Zhao-dong Wang
Mechanical properties and thermal deformation behavior of low-cost titanium matrix composites prepared by a structure-optimized Y2O3 crucible
A porous yttrium oxide crucible with both thermal shock resistance and erosion resistance was developed by structural optimization. The structure-optimized yttrium oxide crucible was proved to be suitable for melting highly reactive titanium alloys. Low-cost (TiB-Y
2
O
3
)-reinforced titanium matrix composites were prepared by vacuum induction melting using the prepared crucible. The thermal deformation behavior and microstructure evolution of (TiB-Y
2
O
3
)-reinforced titanium matrix composites were investigated at deformation temperatures of 900–1100 °C with strain rates of 0.001–1 s
-1
. The results showed that the prepared yttrium oxide crucible had both thermal shock and erosion resistance, the low-cost titanium matrix composites could be prepared by the developed yttrium oxide crucibles which were homogeneous in composition and highly sensitive to strain rate and deformation temperature, and the peak and rheological stresses decreased with increasing deformation temperature or decreasing strain rate. In addition, the average thermal deformation activation energy of the composites was calculated to be 574.6 kJ/mol by establishing the Arrhenius constitutive equation in consideration of the strain variables, and the fitting goodness between the predicted stress value and the measured value was 97.624%. The calculated analysis of the hot processing map showed that the best stable thermal deformation zone was located in the deformation temperature range of 1000–1100 °C and strain rate range of 0.001–0.01 s
-1
, where the peak dissipation coefficient was
η
= 71%. In this zone, the deformation of the reinforcement and matrix was harmonious, the reinforcement was less likely to fracture, dynamic recrystallization occurred more fully and the alloy exhibited near steady rheological characteristics.
2024 Vol. 31 (3): 738-751 [
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752
Yan Qi, Xin Zhang, Jun Li, Dong-liang Zhao, Shi-hai Guo, Yang-huan Zhang
Hydrogen storage thermodynamics and kinetics of as-cast Ce–Mg–Nibased alloy
The reaction kinetics of alloys based on magnesium are known to be greatly improved by the partial substitution of Mg with rare earths and transition metals, particularly Ni. The enhanced superficial hydrogen dissociation rate, the weakened Mg–H bond and the lower activation energy following element replacement are thought to be related to the better performance. The experimental alloys Ce
5
Mg
95-x
Ni
x
(
x
= 5, 10, 15) were smelted by the vacuum induction melting. The phase transformation and structural evolution of experimental alloys before and after reaction with hydrogen were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The cast specimens contain CeMg
12
, Mg and Mg
2
Ni phases, and the increase in Ni content results in an obvious growth of Mg
2
Ni phase. The isothermal and non-isothermal hydrogenation and dehydrogenation kinetics of the experimental specimens were investigated using the Sievert apparatus, differential scanning calorimetry and thermal gravimetric analyzer. The activation energy may be calculated using the Arrhenius and Kissinger equations. The experimental alloys have been shown to have good activation properties, with a reversible hydriding and dehydriding capacities of around 5.0 wt.% in the first cycle. The initial dehydrogenation temperature of MgH
2
decreases from 557.5 to 537.7 K with changing Ni content from 5 to 15 at.%. The dehydrogenation activation energy also reduces from 77.09 to 62.96 kJ/mol, which explains the improved hydrogen storage performance caused by Ni substitution. It can be shown that the impact of Ni on the decomposition enthalpy of MgH
2
is quite modest, with the absolute enthalpy (Δ
H
r
) only decreasing from 78.48 to 76.15 kJ/mol.
2024 Vol. 31 (3): 752-766 [
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767
Hong-bin Dai, Jian Miao, Jia-xin Lin
Grain refinement of 5A06 aluminum alloy welds caused by tungsten inert gas welding arc characteristics under Ar–He alternating gas supply conditions: a coupled method of water-cooled copper plate test/numerical simulation
The welding arc, as a carrier for the conversion of electrical energy to thermal energy, has a direct impact on the quality of welding by its properties and states. In the tungsten inert gas (TIG) welding process under the condition of Ar–He alternating gas supply, the arc is alternately converted between Ar arc and He arc with an alternating gas supply cycle, which has obvious arc change characteristics. The FLUENT software was used to numerically simulate the characteristics of the TIG arc under the condition of alternating gas supply, and the arc temperature field, arc pressure, electric potential and current density distribution under the condition of alternating gas supply were obtained. Combined with the real-time data of arc pressure measured by the water-cooled copper plate with holes, it is proved that the TIG arc has obvious dynamic characteristics under the condition of Ar–He alternating gas supply. This unique dynamic TIG arc acts on the 5A06 aluminum alloy weld, causing the molten pool to stir, resulting in uniform microstructure and grain refinement at the weld, and thereby improving the mechanical properties of the welded joint.
2024 Vol. 31 (3): 767-777 [
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钢铁研究学报(英文版)
News
·
《钢铁研究学报》第二届青年编委招募
·
Call for Papers for the Special Issue on “Corrosion and wear of materials in extreme environments”
·
Call for Papers for the Special Issue on “Resources Recycling of Solid Wastes from Ironmaking and St
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Call for Papers for the Special Issue on “Application of AI in steelmaking and ferrous materials”
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