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Optimizing the low-pressure carburizing process of 16Cr3NiWMoVNbE gear steel

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Journal of Materials Science & Technology 2019年第7期35卷 1218-1227页

作者： Haojie wang Bin wang zhaodong wang Yong Tian R.D.K.Misra State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China Laboratory for Excellence in Advanced Steel Research Department of MetallurgicalMaterials and Biomedical EngineeringUniversity of Texas at El PasoEl PasoTX 79968USA

Compared with the traditional atm ospheric carburization, low-pressure carburization has the benefits of producing no surface oxidation and leaving fine, uniformly dispersed carbides in the carburized layer. However, the process param eters for low-pressure carburization of 16Cr3NiWMoVNbE steel have yet to be optimized. Thus, we use the saturation-value method to optimize these parameters for aviation-gear materials. Toward this end, the m icrostructure and properties of 16Cr3NiWMoVNbE steel after different carburization processes are studied by optical microscopy, scanning electron microscopy, transm ission electron microscopy, and electron probe microanalysis. Considering the saturated austenite carbon concentration, we propose a model of carbon flux and an alloy coefficient for low -pressure carburization to reduce the carbon concentration in austenite and avoid the surface carbide network. At the early stage of carburization (30 s), the gas-solid interface has a higher concentration gradient. The averaging method is not ideal in practical applications, but the carbon flux measured by using the segm ented average m ethod is 2.5 times that measured by the overall average method, which is ideal in practical applications. The corresponding carburization tim e is reduced by 60%. By using the integral average method, the actual carburization time increases, which leads to the rapid form ation of carbide on the surface and affects the entire carburization process. Nb and Wcombine with C to form carbides, which hinders carbon diffusion and consumes carbon, resulting in a sharp decrease in the rate of C diffusion in austenite (the diffusion rate is reduced by 52% for 16Cr3NiWMoVNbE steel). By changing the diffusion coefficient model and comparing the hardness gradient of different processes, the depth of the actual layer is found to be very similar to the design depth.

关键词： 16Cr3NiWMoVNbE steel Low-pressure carburizing Saturated carbon concentration Carbon flux

The determining role of carbon addition on mechanical performance of a non-equiatomic high-entropy alloy

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Journal of Materials Science & Technology 2022年第15期110卷 167-177页

作者： Xiaolin Li Xiaoxiao Hao Chi Jin Qi wang Xiangtao Deng Haifeng wang zhaodong wang State Key Laboratory of Solidification Processing Center of Advanced Lubrication and Seal MaterialsNorthwestern Polytechnical UniversityXi’anShaanxi 710072PR China State Key Laboratory of Rolling and Automation Northeastern UniversityShenyangLiaoning 110819PR China

The mechanical properties and deformation mechanism of a C-doped interstitial high-entropy alloy(i HEA)with a nominal composition of Fe_(49.5)Mn_(29.7)Co_(9.9)Cr_(9.9)C_(1)(at.%)were *** excellent combination of strength and ductility was obtained by cold rolling and *** structure of the alloy is consisted of FCC matrix and randomly distributed Cr_(23)C_(6).For gaining a better understanding of deformation mechanism,EBSD and TEM were conducted to characterize the microstructure of tensile specimens interrupted at different *** low strain(2%),deformation is dominated by dislocations and their partial *** the strain increase to 20%,deformation-driven athermal phase transformation and dislocations slip are the main deformation *** at high strain of 35%before necking,deformation twins have been observed besides the HCP *** simultaneous effect of phase transformation(TRIP effect)and mechanical twins(TWIP effect)delay the shrinkage,and improve the tensile strength and ***'s more,compared with the HEA without C addition,the yield strength of the C-doped i HEA has been improved,which can be attributed to the grain refinement strengthening and precipitation *** with the lattice friction and solid solution strengthening,the theoretical calculated values of yield strength match well with the experimental results.

关键词： Interstitial high-entropy alloy Precipitation strengthening Mechanical properties Phase transformation Mechanical twins

Microstructure and elevated-temperature mechanical properties of dispersoid-strengthened Al-Mg-Si-Mn alloys produced by twin roll casting

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Progress in Natural Science:Materials International 2021年第5期31卷 705-713页

作者： Yong Li Haiyao wang Xiaoming Qian zhaodong wang Guangming Xu Jiadong Li State Key Laboratory of Rolling and Automation Northeastern University Guangxi Advanced Aluminum Processing Innovation Center Co.LTD National Engineering Research Center for Equipment and Technology of Cold Strip Rolling Yanshan University Key Laboratory of Electromagnetic Processing of Materials Ministry of Education Northeastern University

The microstructure and elevated-temperature mechanical properties of dispersoid-strengthened Al-Mg-Si-Mn alloys produced by twin roll casting(TRC) and conventional mold casting(MC) were studied. A specific heat treatment at 430℃ for 6 h was applied, followed by rolling. Tensile tests were carried out at 300℃. The results show that in the as-cast microstructures, equiaxed grains formed in the MC sample while elongated grains with substructures formed in the TRC sample. The eutectics in the TRC sample were much finer than those in the MC sample. Upon heat treatment, large numbers of α-Al(Fe, Mn)Si dispersoids precipitated, and the TRC sample had a greater number density of dispersoids than those in the MC sample. During the tensile test after rolling, the TRC samples exhibited higher strength than the MC samples, which resulted from the combination of the strengthening effect of the stronger dispersoids and the greater substructure hardening effect in the TRC sample; the TRC sample exhibited better ductility due to its finer initial eutectic than that in the MC sample, which depressed the stress concentration and delayed the occurrence of microcracks and fracture in the TRC sample.

关键词： Aluminum alloy Twin-roll casting (TRC) α-Al(Fe Mn)Si dispersoids Elevated-temperature

Cell-nucleus structured electrolyte for low-temperature aqueous zinc batteries

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Journal of Energy Chemistry 2023年第8期83卷 324-332,I0010页

作者： Yang Dong Ning Zhang zhaodong wang Jinhan Li Youxuan Ni Honglu Hu Fangyi Cheng Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education) Engineering Research Center of High-efficiency Energy Storage(Ministry of Education)College of ChemistryNankai UniversityTianjin 300071China Haihe Laboratory of Sustainable Chemical Transformations Tianjin 300192China College of Chemistry and Materials Science Analytical Science and Technology of Hebei ProvinceHebei UniversityBaoding 071002HebeiChina

Rechargeable aqueous zinc(Zn) batteries hold great promise for large-scale energy storage,but their implementation is plagued by poor Zn reversibility and unsatisfactory low-temperature ***,we design a cell-nucleus structured electrolyte by introducing low-polarity 1,2-dimethoxyethane(DME) into dilute 1 M zinc trifluoromethanesulfonate(Zn(OTf)_(2)) aqueous solution,which features an OTf--rich Zn2^(+)-primary solvation sheath(PSS,inner nucleus) and the DMEmodulated Zn^(2+)-outer solvation sheath(outer layer).We find that DME additives with a low dosage do not participate in the Zn2+-PSS but reinforce the Zn-OTf-coordination,which guarantees good reaction kinetics under ultralow ***,DME breaks the original H-bonding network of H2O,depressing the freezing point of electrolyte to-52.4℃.Such a cell-nucleus-solvation structure suppresses the H_(2)O-induced side reactions and forms an anion-derived solid electrolyte interphase on Zn and can be readily extended to 1,*** as-designed electrolyte enables the Zn electrode deep cycling stability over 3500 h with a high depth-of-discharge of 51.3% and endows the Zn‖V_(2)O_(5)full battery with stable cycling over 1000 cycles at 40℃.This work would inspire the solvation structure design for low-temperature aqueous batteries.

关键词： Aqueous zinc batteries Low temperature Cell-nucleus solvation structure Zn metal anode Solid electrolyte interphase

Microstructure Characteristics and Elevated Temperature Mechanical Properties of a B Containedβ-solidifiedγ-TiAl Alloy

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Journal of Wuhan University of Technology(Materials Science) 2024年第3期39卷 738-746页

作者：王秀琦 GUO Ruiqi 刘国怀 LI Tianrui YANG Yuxuan CHEN Yang XIN Meiling wang zhaodong State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China School of Materials Science and Engineering Harbin Institute of Technology at ShenzhenShenzhen 518055China School of Metallurgical Engineering Anhui University of TechnologyMaanshan 243000China

The improved microstructure and enhanced elevated temperature mechanical properties of Ti-44Al-5Nb-(Mo,V,B)alloys were obtained by vacuum arc re-melting(VAR)and primary annealing heat treatment(HT)of 1260℃/6 h/Furnace cooling(FC).The phase transformation,microstructure evolution and tensile properties for as-cast and HTed alloys were *** indicate that three main phase transformation points are determined,T_(eut)=1164.3℃,T_(γsolv)=1268.3℃and T_(βtrans)=1382.8℃.There are coarse lamellar colonies(300μm in length)and neighbor reticular B2 andγgrain(3-5μm)in as-cast alloy,while lamellar colonies are markedly refined and multi-oriented(20-50μm)as well as the volume fraction and grain sizes of equiaxedγand B2 phases(about 15μm)significantly increase in as-HTed *** transformations involvingα+γ→α+γ+β/B2 and discontinuousγcoarsening contribute to the above ***(1-3μm)act as nucleation sites forβ_(eutectic) and produce massiveβgrains with different orientations,thus effectively refining the lamellar colonies and forming homogeneous multi-phase *** curves show both the alloys exhibit suitable performance at 800℃.As-cast alloy shows a higher ultimate tensile stress of 647 MPa,while a better total elongation of more than 41%is obtained for as-HTed *** mechanical properties improvement is mainly attributed to fine,multi-oriented lamellar colonies,coordinated deformation of homogeneous multi-phase microstructure and borides within lamellar interface preventing crack propagation.

关键词： TiAl alloy phase transformation heat treatment boride microstructure mechanical properties

A novel investigation on the influence of Cu–P modifier on the microstructure, mechanical performance, and melting process of Al–50Si alloys treated by overheating

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Progress in Natural Science:Materials International 2021年第3期31卷 461-470页

作者： Tao Jiang Chuang Yu Boyue Xu Wei Yu Guangming Xu Yong Li zhaodong wang Guodong wang Key Laboratory of Electromagnetic Processing of Materials of Ministry of Education Northeastern University State Key Laboratory of Rolling and Automation Northeastern University

As an efficient modifier, phosphorus(P) can significantly reduce the size of primary silicon(Si) crystals. However,modifier can aggregate when the P content exceeds a certain proportion, which decreases refining efficiency. In this study, the evolution of microstructures and mechanical properties of Al–50 Si alloy have been studied by combining superheating and modification treatments. After modification, the mean size of the primary Si phase increased with superheating temperature, while the hardness decreased with increased superheating. Although the alloy was in an over-modified state when the modified content was 7 wt%, the overall alloy hardness was the highest. Nanoindentation tests were used to examine the mechanical properties of each alloy phase and the results showed that the nano-hardness of Al2Cu phase was 5.52 GPa, three times that of an Al matrix, and was considered to be the reason for increased alloy hardness after over-modification. This phenomenon indicated that, except for size and distribution of the primary Si phase, intermetallic compounds, such as Al2Cu, also played important roles in modifying alloy mechanical properties. The alloy melting process was observed in-situ using a laser confocal high-temperature scanning microscope and results indicated that the melting temperature of α-Al decreased with increased matrix Cu content. A model for calculating distortion energy was proposed and its rationality *** results showed that, with increased matrix Cu content, the distortion energy gradually increased,which was the main reason for decreased matrix melting temperature. Moreover, the existence of distortion energy was verified using the EBSD method.

关键词： Al–50Si alloy Nano-indentation In-situ observation Distortion energy

Impact of thermal exposure on the microstructure and mechanical properties of a twin-roll cast Al-Mn-Fe-Si strip

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Journal of Materials Science & Technology 2022年第12期107卷 183-196页

作者： Jie Kuang Xiaolong Zhao Yuqing Zhang Jinyu Zhang Gang Liu Jun Sun Guangming Xu zhaodong wang State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China

Al-Mn-Fe-Si strips were fabricated via both the twin-roll casting(TRC)and the more conventional route,direct-chill casting(DC).The two types of strips prepared were subjected to thermal exposure at a series of *** tensile tests after the thermal exposure showed that while the DC strip presented a~74%decrease in the yield strength and~35%decrease in the ultimate tensile strength(UTS)after being exposed to 350℃for 12 h,the TRC strip,in contrast,maintained its strength at temperatures up to~460℃ for the same *** microstructure characterization revealed that the different thermal stability in the strength of the two types of strips arised from their distinct evolution in grain morphology and second phase particles during the thermal *** calculation based on Cahn-Lücke-Stüwe(CLS)model suggested that due to the highly supersaturated solute atoms,at the beginning of the thermal exposure,the TRC strip experienced a strong solute drag which reduced the grain boundary migrating velocity to a value that is orders of magnitude smaller than that in the DC *** the progress of the thermal exposure,the solute atoms precipitated out,forming densely distributed second phase *** one thing,these particles stabilized the grain structure by inducing Zener pinning pressure which could be ten times higher than that in the DC strip,depending on the *** another,they acted as dislocation obstacles and compensated for the strength loss owing to decreasing solution *** effects contributed to the TRC strip’s fairly stable strength regarding thermal exposure below 460°*** present work could guide the direct application of the TRC strips in the *** results should also be helpful for the development of a fundamental framework for designing advanced TRC Al strips with improved mechanical properties at elevated temperatures.

关键词： Al-Mn-Fe-Si strip Twin-roll casting Thermal stability Ductile fracture

Generalized stability criterion for controlling solidification segregation upon twin-roll casting

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Journal of Materials Science & Technology 2023年第3期134卷 163-177页

作者： Pan Wu Yubing Zhang Jiaqi Hu Shaojie Song Yong Li Huiyuan wang Guo Yuan zhaodong wang Shizhong Wei Feng Liu State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Analytical and Testing Center Northwestern Polytechnical UniversityXi’an 710072China State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China State Key Laboratory of Super hard Materials Jilin UniversityChangchun 130012China National Joint Engineering Research Center for Abrasion Control and Molding of Metal Materials Henan University of Science and TechnologyLuoyang 471003China

Macro-and micro-segregation formed upon twin-roll casting(TRC)can be inherited from sub-rapid solid-ification to solid-state transformation,even to plastic deformation,thus deteriorating drastically mechan-ical properties of as-produced thin *** many works focusing mainly on controlling fields of thermal,concentration and convection have been reported,how to control artificially and quantitatively the segregation using a theoretical connection between processing parameters and solidification models,has not been realized,*** it,a systematical framework integrating non-equilibrium dendritic growth and overall solidification kinetics with the TRC parameters,was constructed applying a general-ized stability(GS)conception deduced from transient thermodynamic driving force△G^(t)and transient ki-netic energy barrier Q_(eff)^(t)evolving upon *** from this framework considering synergy of thermodynamics and kinetics(i.e.,thermo-kinetic synergy),a criterion of high△G^(t)-high GS guaranteed that the macro(i.e.,the centerline)and the micro(i.e.,the edge)segregation can be suppressed by in-creasing△G^(t)and GS at the beginning and the ending stage of sub-rapid solidification,*** typical thermo-kinetic combination producing the microstructure can be inherited into the plastic de-formation,as reflected by corresponding strength-ductility *** work realized quantitative controlling of TRC by a theoretical connection between processing parameters and solidification models,where,an optimization for sub-rapid solidification segregation using the GS conception including△G^(t)and Q_(eff)^(t)has been performed.

关键词： Segregation Sub-rapid solidification Generalized stability Twin-roll casting Thermo-kinetics

An Effective Optimized Strategy on Speed Fluctuation Suppression for Air Conditioner Compressor 36

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An Effective Optimized Strategy on Speed Fluctuation Suppres...