Grain refinement of Mg-Ca alloys by native MgO particles

In Mg-Ca alloys the grain refining mechanism,in particular regarding the role of nucleant substrates,remains the object of debates.Although native MgO is being recognised as a nucleating substrate accounting for grain refinement of Mg alloys,the possible interactions of MgO with alloying elements that may alter the nucleation potency have not been elucidated yet.Herein,we design casting experiments of Mg-xCa alloys varied qualitatively in number density of native MgO,which are then comprehensively studied by advanced electron microscopy.The results show that grain refinement is enhanced as the particle number density of MgO increases.The native MgO particles are modified by interfacial layers due to the co-segregation of Ca and N solute atoms at the MgO/Mg interface.Using aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy,we reveal the nature of these Ca/N interfacial layers at the atomic scale.Irrespective of the crystallographic termination of MgO,Ca and N co-segregate at the MgO/Mg interface and occupy Mg and O sites,respectively,forming an interfacial structure of a few atomic layers.The interfacial structure is slightly expanded,less ordered and defective compared to the MgO matrix due to compositional deviations,whereby the MgO substrate is altered as a poorer template to nucleate Mg solid.Upon solidification in a TP-1 mould,the impotent MgO particles account for the grain refining mechanism,where they are suggested to participate into nucleation and grain initiation processes in an explosive manner.This work not only reveals the atomic engineering of a substrate through interfacial segregation but also demonstrates the effectiveness of a strategy whereby native MgO particles can be harnessed for grain refinement in Mg-Ca alloys.

Engineering fibrillar morphology for highly efficient organic solar cells

The power conversion efficiency(PCE)for single-junction organic solar cells(OSCs),wherein the photoactive layer is a typical bulk-heterojunction containing donor and acceptor materials,has surpassed 19%[1−4].The advance is ascribed to the development of Y-series non-fullerene acceptors(NFAs)[5,6]and polymer donors[7−13],and the refined control of the blend film morphology.

Dissolution behavior of Al_(2)O_(3)inclusions into CaO-MgO-SiO_(2)-Al_(2)O_(3)-TiO_(2)system ladle slags

To investigate the dissolution behaviors of Al_(2)O_(3)inclusions in CaO-5wt%MgO-SiO_(2)-30wt%Al_(2)O_(3)-TiO_(2)system ladle slags,confocal scanning laser microscopy was conducted on the slags with different TiO_(2)contents(0-10wt%),and scanning electron microscopy was performed to study the interfacial reaction between Al_(2)O_(3)and this slag system.The results disclose that the dissolution of Al_(2)O_(3)inclusions does not result in the formation of new phases at the boundary between the slag and the inclusions.In TiO_(2)-bearing and TiO_(2)-free ladle slags,there is no difference in the dissolution mechanism of Al_(2)O_(3)inclusions at steelmaking temperatures.Boundary layer diffusion is found as the controlling step of the dissolution of Al_(2)O_(3),and the diffusion coefficient is in the range of 4.18×10^(-10)to 2.18×10^(-9)m^(2)/s at 1450-1500℃.Compared with the solubility of Al_(2)O_(3)in the slags,slag viscosity and temperature play a more profound role in the dissolution of Al_(2)O_(3)inclusions.A lower viscosity and a lower melting point of the slags are beneficial for the dissolution.Suitable addition of TiO_(2)(e.g.,5wt%)in ladle slags can enhance the dissolution of Al_(2)O_(3)inclusions because of the low viscosity and melting point of the slags,while excessive addition of TiO_(2)(e.g.,10wt%)shows the opposite trend.

Application of novel constrained friction processing method to produce fine grained biomedical Mg-Zn-Ca alloy

In order to obtain Mg alloys with fine microstructures and high mechanical performances,a novel friction-based processing method,name as“constrained friction processing(CFP)”,was investigated.Via CFP,defect-free Mg-Zn-Ca rods with greatly refined grains and high mechanical properties were produced.Compared to the previous as-cast microstructure,the grain size was reduced from more than 1 mm to around 4μm within 3 s by a single process cycle.The compressive yield strength was increased by 350%while the ultimate compressive strength by 53%.According to the established material flow behaviors by“tracer material”,the plastic material was transported by shear deformation.From the base material to the rod,the material experienced three stages,i.e.deformation by the tool,upward flow with additional tilt,followed by upward transportation.The microstructural evolution was revealed by“stop-action”technique.The microstructural development at regions adjacent to the rod is mainly controlled by twinning,dynamic recrystallization(DRX)as well as particle stimulated nucleation,while that within the rod is related to DRX combined with grain growth.

Brent vs.West Texas Intermediate in the US petro derivatives price formation

In this paper,we apply the spatial panel model to explore the relationship between the dynamic of two types of crude oil prices(WTI and Brent crude oil)and their refined products over time.Considering the turbulent months of 2011,when Cushing Oklahoma had reached capacity and the crude oil export ban removal in 2015 as breakpoints,we apply this method both in the full sample and the three resultant regimes.First,results suggest our results show that both WTI and Brent display very similar behaviour with the refined products.Second,when attending to each regime,results derived from the first and third regimes are quite similar to the full sample results.Therefore,during the second regime,Brent crude oil became the benchmark in the petrol market,and it influenced the distillate products.Furthermore,our model can let us determine the price-setters and price-followers in the price formation mechanism through refined products.These results possess important considerations to policymakers and the market participants and the price formation.

Effect of nano-CaO particle on the microstructure,mechanical properties and corrosion behavior of lean Mg-1Zn alloy

The effects of nano-CaO contents on the microstructure,mechanical properties and corrosion resistance of lean Mg-1Zn alloy were investigated.The results showed that the addition of nano-CaO significantly refined the grain size and improved mechanical properties of the Mg-1Zn alloy.At the same time,CaO reacted with molten Mg in situ to form nano-MgO,whose corrosion product in SBF solution was the same with the degradation product of Mg matrix,resulting in the enhanced compactness of the Mg(OH)_(2) layer and reduced corrosion rate of matrix.The Mg-1Zn alloy had lower corrosion resistance due to excessively large grain size and shedding of corrosion products.The composite with 0.5 wt.%CaO had the best corrosion resistance with a weight loss of 9.875 mg·y^(-1)·mm^(-2)due to the small number of Ca_(2)Mg_(6)Zn_(3) phase and suitable grain size.While for composites with high content of CaO(0.7 wt.%and 1.0 wt.%),they had lower corrosion resistance due to the coexistence of large number of Ca_(2)Mg_(6)Zn_(3) and Mg_(2)Ca at grain boundaries,especially for 1.0 wt.%CaO composite,resulting from the strong micro-galvanic corrosion.

Exact solution for thermal vibration of multi-directional functionally graded porous plates submerged in fluid medium

An analytical method for analyzing the thermal vibration of multi-directional functionally graded porous rectangular plates in fluid media with novel porosity patterns is developed in this study.Mechanical properties of MFG porous plates change according to the length,width,and thickness directions for various materials and the porosity distribution which can be widely applied in many fields of engineering and defence technology.Especially,new porous rules that depend on spatial coordinates and grading indexes are proposed in the present work.Applying Hamilton's principle and the refined higher-order shear deformation plate theory,the governing equation of motion of an MFG porous rectangular plate in a fluid medium(the fluid-plate system)is obtained.The fluid velocity potential is derived from the boundary conditions of the fluid-plate system and is used to compute the extra mass.The GalerkinVlasov solution is used to solve and give natural frequencies of MFG porous plates with various boundary conditions in a fluid medium.The validity and reliability of the suggested method are confirmed by comparing numerical results of the present work with those from available works in the literature.The effects of different parameters on the thermal vibration response of MFG porous rectangular plates are studied in detail.These findings demonstrate that the behavior of the structure within a liquid medium differs significantly from that within a vacuum medium.Thereby,they offer appropriate operational approaches for the structure when employed in various mediums.

Integrated multi-scale approach combining global homogenization and local refinement for multi-field analysis of high-temperature superconducting composite magnets

Second-generation high-temperature superconducting(HTS)conductors,specifically rare earth-barium-copper-oxide(REBCO)coated conductor(CC)tapes,are promising candidates for high-energy and high-field superconducting applications.With respect to epoxy-impregnated REBCO composite magnets that comprise multilayer components,the thermomechanical characteristics of each component differ considerably under extremely low temperatures and strong electromagnetic fields.Traditional numerical models include homogenized orthotropic models,which simplify overall field calculation but miss detailed multi-physics aspects,and full refinement(FR)ones that are thorough but computationally demanding.Herein,we propose an extended multi-scale approach for analyzing the multi-field characteristics of an epoxy-impregnated composite magnet assembled by HTS pancake coils.This approach combines a global homogenization(GH)scheme based on the homogenized electromagnetic T-A model,a method for solving Maxwell's equations for superconducting materials based on the current vector potential T and the magnetic field vector potential A,and a homogenized orthotropic thermoelastic model to assess the electromagnetic and thermoelastic properties at the macroscopic scale.We then identify“dangerous regions”at the macroscopic scale and obtain finer details using a local refinement(LR)scheme to capture the responses of each component material in the HTS composite tapes at the mesoscopic scale.The results of the present GH-LR multi-scale approach agree well with those of the FR scheme and the experimental data in the literature,indicating that the present approach is accurate and efficient.The proposed GH-LR multi-scale approach can serve as a valuable tool for evaluating the risk of failure in large-scale HTS composite magnets.

From“Car Priority”to“People Priority”: Exploring New Ideas for Refined Road Space Design

Roads are crucial public spaces in cities and serve as a window to showcase the city’s characteristics.They serve not only as a means of urban transportation but also as a crucial spatial carrier for urban communication activities and a significant location for meeting the increasing demands of people for a better quality of life.The current road infrastructure prioritizes the right of way for cars,neglecting the design of sidewalks and green belts within the road’s boundaries,and extension spaces between buildings and boundary lines of roads.There is a pressing need to improve street space in response to the demand for development transformation and the creation of a warmer city.This paper summarizes common problems in current road spaces,draws on the experience of excellent urban road spaces in foreign countries,discusses new ideas for the refined design of road spaces based on the transformation of road planning concepts,and suggests a reference standard for guiding detailed design.Simultaneously,the review of road construction will incorporate the detailed design of road space to enhance the role of planning in guiding and controlling the construction of road works.

Application of Automation and Intellectualization Technology in Steelmaking Plant

Steelmaking plant of Fujian San Gang min Guang Co.,Ltd.is keeping pace with the trend of the times.Under the new situation that the labor cost is rising day by day.Constantly introducing intelligent technology to improve the level of automation operation and reducing labor intensity of staff and workers.Especially under the support of MES information system.Advanced and practical technology is adopted in converter,refining and continuous casting process.In recent years,production management and control,energy management and control,material tracking,cost control and equipment operation and maintenance and reducing personnel to new achieve-ments in reducing personnel.

Exploration and Practice of Nitrogen Addition Process for LF Refining Ladle Bottom Blowing Nitrogen Steel Liquid

This article discusses and analyzes the law of nitrogen increase in liquid steel and the main factors affect-ing the nitrogen increasing of molten steel,through the way of adding nitrogen to molten steel by bottom blowing nitrogen gas in LF refining process.It is considered that the main factors affecting the nitrogen increasing instability of molten steel are the initial temperature of LF refining,nitrogen relative element,surface active elements[O]and[S]of steel liquid,and bottom blowing rate of ladle.The large-scale production practice shows that T[O]not more than 50×10-6 and[S]is not more than 0.020 in LF refining at the initial temperature of not less than 1570.The liquid steel nitrogen enrichment test is carried out by ladle bottom blowing nitrogen gas after 20 min of refining,the flow rate is set as(6.0~7.0)NL/min per ton,and it is turned to 2 NL/min at 6 min before the end of refining,the nitrogen increasing rate of liquid steel is basically stable at(5~6)×10-6 per minute.

Evaluation of the Impact of Refined Quality Control Management Model on the Qualified Rate of Disinfection and Sterilization of Surgical Instruments in the Sterilization Supply Center

Objective:To evaluate the application value of a refined quality control management model for a sterilization supply center.Methods:A retrospective analysis was conducted on the work situation of the sterilization supply center from January 2021 to January 2023.The work situation before January 31,2022,was classified as the control group;a routine quality control management model was implemented,and the work situation after January 31,2022,was classified as the observation group.The quality of medical device management and department satisfaction between the two groups were compared.Results:The timely recovery and supply rate,classification and cleaning pass rate,disinfection pass rate,packaging pass rate,sterilization pass rate,and department satisfaction score in the observation group were all higher than those of the control group(P<0.05).Conclusion:Implementing a refined quality control management model in the sterilization supply center can improve the quality management level of medical devices and department satisfaction and is worthy of promotion.

Effect of grain refinement induced by wire and arc additive manufacture (WAAM) on the corrosion behaviors of AZ31 magnesium alloy in NaCl solution

Additive manufacturing(AM)of Mg alloys has become a promising strategy for producing complex structures,but the corrosion performance of AM Mg components remains unexploited.In this study,wire and arc additive manufacturing(WAAM)was employed to produce single AZ31 layer.The results revealed that the WAAM AZ31 was characterized by significant grain refinement with non-textured crystallographic orientation,similar phase composition and stabilized corrosion performance comparing to the cast AZ31.These varied corrosion behaviors were principally ascribed to the size of grain,where cast AZ31 and WAAM AZ31 were featured by micro galvanic corrosion and intergranular corrosion,respectively.

In situ observation of the dissolution kinetics of Al_(2)O_(3) particles in CaO–Al_(2)O_(3)–SiO_(2) slags using laser confocal scanning microscopy

The dissolution kinetics of Al_(2)O_(3) in CaO-Al_(2)O_(3) SiOslags was studied using a high-temperature confocal scanning laser microscope at 1773 to 1873 K.The results show that the controlling step during the Al_(2)O_(3) dissolution was the diffusionin molten slag.It was found that the dissolution curves of Al_(2)O_(3) particles were hardly agreed with the traditional boundary layer diffusion model with the increase of the CaO/Al_(2)O_(3) ratio of slag.A modified diffusion equation considering slag viscosity was developed to study the dissolution mechanism of Al_(2)O_(3) in slag.Diffusion coefficients of Al_(2)O_(3) in slag were calculated as 2.8×10to 4.1×10m~2/s at the temperature of 1773-1873 K.The dissolution rate of Al_(2)O_(3) increased with higher temperature,CaO/Al_(2)O_(3),and particle size.A new model was shown to be v_(Al_(2)O_(3))=0.16×r_(0)^(1.58)×x^(3.52)×(T-T_(mp))^(1.11)to predict the dissolution rate and the total dissolution time of Al_(2)O_(3) inclusions with various sizes,where vAl_(2)O_(3) is the dissolution rate of Al_(2)O_(3) in volume,μm^(3)/s;x is the value of CaO/Al_(2)O_(3) mass ratio;R_(0) is the initial radius of Al_(2)O_(3),μm;T is the temperature,K;T_(mp) is the melting point of slag,K.

Effect of rare earth on morphology and dispersion of TiB2 phase in Al-Ti-B alloy refiner

To investigate the effect of rare earth on size and distribution of TiB2 phase in aluminum alloy refiner,Al-5Ti-1B-RE master alloy was fabricated,and its microstructure and phase constitutions were investigated by the combination of first principles calculations and experimental investigation.The calculated results reveal that Ce has the most effective modification ability due to the most positive adsorption energy and the largest charge transfer value compared with other rare earth elements.Results of experimental investigation indicate that the addition of rare earth in the Al-5Ti-1B alloys can greatly refine the particle size of TiB2,improve the distribution of particles and lead to better refinement effect than that of the Al-5Ti-1B alloys without rare earth.Moreover,Ce has the best optimization effect,which agrees well with the calculated results.

Refined Aerodynamic Test of Wide-Bodied Aircraft and Its Application

The large dual-channel wide-bodied aircraft has a long range and a high cruise Mach number.Therefore,its aerodynamic design requires a high level ofwind tunnel test refinement.Based on the requirements of aerodynamic design for the future wide-bodied aircraft and the characteristics of high-speed wind tunnel tests,the error theory is introduced to analyze the factors affecting the accuracy of the test data.This study carries out a series of research on the improvement of refined aerodynamic test technology in an FL-26 wind tunnel,including design and optimization of the support system of wide-bodied aircraft,model attitude angle measurement,Mach number control accuracy,measurement and control system stability,test data correction and perfection,high-precision force balance and standard model development.In addition,the effect of the standard specification of the refined aerodynamic test is investigated to improve the data quality.The research findings have been applied in the standard model test and subsequent models of wide-bodied aircraft.The results show that whenMach numbers are less than 0.9,the control accuracy of Mach numbers in the FL-26 wind tunnel is smaller than 0.001 and the measurement error of attack angle is smaller than 0.01°.Therefore,it has the ability to correct the data influenced by factors,such as support/wall interference,model deformation,floating resistance and airflow deflection angle.The repeatability accuracy of the standard model’s comparison test shows that the lift coefficient is less than or equal to 0.0012,the drag coefficient is less than or equal to 0.00004,pitching moment coefficient is less than or equal to 0.0004.The bending resolution of the model’s deformation measurement is less than 0.2 mm,and the tensional deformation is smaller than 0.04°.The revised aerodynamic data and model deformation measurement results have good agreement with that of the ETW wind tunnel.The results demonstrate that the improved technology presented in this paper can significantly enhance the refined aerodynamic test of wide-bodied aircraft.

Effect of gas blowing nozzle angle on multiphase flow and mass transfer during RH refining process

A three-dimensional mathematical model was developed to investigate the effect of gas blowing nozzle angles on multiphase flow,circulation flow rate,and mixing time during Ruhrstahl-Heraeus(RH) refining process.Also,a water model with a geometric scale of 1:4 from an industrial RH furnace of 260 t was built up,and measurements were carried out to validate the mathematical model.The results show that,with a conventional gas blowing nozzle and the total gas flow rate of 40 L·min^(-1),the mixing time predicted by the mathematical model agrees well with the measured values.The deviations between the model predictions and the measured values are in the range of about 1.3%–7.3% at the selected three monitoring locations,where the mixing time was defined as the required time when the dimensionless concentration is within 3% deviation from the bath averaged value.In addition,the circulation flow rate was 9 kg·s^(-1).When the gas blowing nozzle was horizontally rotated by either 30° or 45°,the circulation flow rate was found to be increased by about 15% compared to a conventional nozzle,due to the rotational flow formed in the up-snorkel.Furthermore,the mixing time at the monitoring point 1,2,and 3 was shortened by around 21.3%,28.2%,and 12.3%,respectively.With the nozzle angle of 30° and 45°,the averaged residence time of 128 bubbles in liquid was increased by around 33.3%.

Effect of Co on Microstructure Transformation and Refinement Mechanism of Undercooled Cu-Ni Alloy

Both Cu60Ni38Co2 and Cu60Ni40 alloy were naturally cooled after rapid solidification from the liquid phase.The transformation law of the microstructure characteristics of the rapidly solidified alloy with the change of undercooling(DT)was systematically studied.It was found that the two alloys experienced the same transformation process.The refinement structures under different undercoolings were characterized by electron backscatter diffraction(EBSD).The experimental results show that the characteristics of the refinement structure of the two alloys with low undercooling are the same,whereas,the characteristics of the refinement structure with high undercooling are opposite.The transmission electron microscope(TEM)results of Cu60Ni38Co2 alloy show that the dislocation network density of low undercooled microstructure is lower than that of high undercooled microstructure.By combining EBSD and TEM,it can be confirmed that the dendrite remelting fracture is the reason for the refinement of the low undercooled structure,while the high undercooled structure is refined due to recrystallization.

Influence of strain rate on grain refinement and texture evolution under complex shear stress conditions

The effects of different complex shear stress conditions on grain refinement and texture evolution of Mg-13Gd-4Y-2Zn-0.5Zr alloy were investigated.With increasing strain rate,the average grain size of compression-shear(CS)and compression-torsion(CT)samples are decreased,and the grain size of dynamic recrystallization(DRX)grains is also decreased.This is because that the precipitation number ofβphases is increased,and the hindering effect on grain growth can be significantly enhanced.The DRX fractions of CS and CT samples are decreased with increased strain rate.The low DRX fraction at high strain rate is related to the insufficient time for grains to nucleate.The DRX process can be promoted by the PSN mechanism of second phases,and the grain growth can be restricted by the pinning effect.At the same time,the texture strength is enhanced as the strain rate increased.Besides,the kinking degree of lamellar long-period stacking ordered(LPSO)phases is increased.Under complex shear stress conditions,non-basal slip,especially pyramidal slip,is easily activated and the texture is deflected greatly.Compared with the CS samples,CT samples have smaller average grain size,higher DRX fraction,and lower texture strength for a certain strain rate.This is because that the equivalent stress of the CT sample is larger,the stress triaxiality is smaller,so more serious dislocations are piled up near grain boundaries and second phases.At the same time,since CT sample was sheared with torsion,the dislocation movement path can be called“rotational dislocation accumulation”,and the longer distribution path of the CT sample is generated,so more sub-grains and low-angle grain boundaries(LAGBs)are formed.Compared with the CS sample,more huge-angle grain boundaries(HAGBs)and DRX grains are formed from grain boundary to grain interior,so better grain refinement effect is achieved.

Effect of solute atom adsorption on heterogeneous nucleation by in-situ MgO particles:Experimental and theoretical studies

The introduction of oxide inclusions during the smelting process has a clear promising heterogeneous nucleation potency on Mg-based alloys, but the mechanism has not been explored clearly yet. In the present work, the grain refinement mechanism of MgO in pure Mg,Mg-3Al and AZ31(Mg-2.9Al-0.9Zn-0.3Mn) alloys is investigated by combing first-principles calculations and experiments. The theoretical results show that solute atoms adsorption will affect the nucleation and the subsequent growth process, which is an important factor affecting the refinement efficiency. A contradiction between the experimental results and the grain growth restriction factor(GRF) theory is observed,that is the refinement ratio of AZ31 is worse than Mg-3Al alloy. This is explained by an adsorption model which reveals that Al promotes the adsorption of Mg on MgO surface so as to stimulate more particles available as nucleating sites. Meanwhile, Fe and Mn also have favorable effects on the adsorption of Mg, Zn may play the opposite role compared to Al. The theoretical analyzes provide a strong support to the experiments that Al benefits the initial nucleation of α-Mg on MgO to promote the grain refining effect of Mg-3Al prior to AZ31 alloy.