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Journal of Iron and Steel Research(International) 2024年第4期31卷 924-932页

作者： Wei liu Yan Wang Li-xiong Han Ying-kang Wei Hui-ping Tang shi-feng liu School of Metallurgical Engineering Xi'an University of Architecture and TechnologyXi'an 710055ShaanxiChina School of Engineering Zhejiang University City CollegeHangzhou 310015ZhejiangChina

The oxygen content of metal powder is decisive for the recyclability of powder.The research on the effect of oxygen content on powder properties and material formability has practical significance for economical production with additive manufacturing while preventing the waste of resources.Here,we deliberately oxidized the powder by baking at high temperature to increase the oxygen content in the powder and gave the calculation method of the oxygen content in the powder oxidation film.The majority of oxygen element was found in the oxide particles in the powder and the oxide flm on the powder surface,which did affect the flowability of the powder.It is worth noting that the increase in the oxygen content does not change the phase of H13 steel,but it can promote the molten pool flow and obtain a smoother surface.The increase in the oxygen content in the powder is not the decisive factor for the formability and defects of the printed samples.It is the combined effect of the powder deformation,the increase in the oxygen content,and the impurity pollution after repeated use,which leads to the limitation of repeated utilization of the powder.

关键词： Additive manufacturing Electron beam melting H13 steel powder-Powder oxidation

Effect of heat treatment on microstructural evolution,mechanical properties and tribological properties of H13 steel prepared using selective laser melting

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Journal of Iron and Steel Research(International) 2024年第5期31卷 1246-1259页

作者： Li-xiong Han Yan Wang shi-feng liu Zhao-hui Zhang Wei liu Xin Yang Dang-shen Ma Jian Zhou Ying-kang Wei College of Metallurgical Engineering Xi’an University of Architecture and TechnologyXi’an710055ShaanxiChina Zhejiang University City College Hangzhou310015ZhejiangChina China Iron and Steel Research Institute Group Co. Ltd.Beijing100081China

H13 tool steel was successfully prepared by selective laser melting(SLM)technology.The effects of heat treatment on the microstructure,mechanical properties,and tribological properties of SLMed H13 steel were investigated.The heat treatment process involved a solution treatment and a double aging treatment of the deposited H13 tool steel prepared by SLM.The aim is to optimize the microstructure and mechanical properties of SLMed H13 steel.Due to the rapid heating and cooling effects of SLM,carbide precipitation in the deposited H13 steel was not uniform and residual stresses were present.The purpose of the solution treatment is to dissolve the solution at a high temperature to eliminate the residual stresses and defects introduced by the SLM-forming structure.The solution treatment and first aging treatment produced the precipitation of small carbides at the grain boundaries and inside the crystals,which increased the hardness of SLMed H13 steel.The hardness increased from 538±4.0 HV of the as-deposited sample to 548±5.8 HV of samples after the first aging treatment.Accordingly,the ultimate tensile strength and the elongation at break decreased from 1882 MPa and 11.5%in the as-deposited sample to 1697 MPa and 7.9%in those after the first aging treatment,respectively.Furthermore,the friction coefficient and wear rate in the as-deposited sample decreased from 0.5160 and 2.36×10^(–6)mm^(−3)N^(−1)m^(−1)to 0.4244 and 1.04×10^(–6)mm^(−3)N^(−1)m^(−1),respectively.However,the distribution of carbides inside the crystals was not uniform.The second aging treatment adjusted the morphology of carbide precipitation and made it more uniform,but the precipitation of carbides grew and settled at the bottom of the grain boundaries.The hardness decreased to 533±6.7 HV compared with that with the first aging treatment,but the ultimate tensile strength and plasticity reached a balance(1807 MPa,14.05%).Accordingly,the friction coefficient and wear rate also showed a stable and decreasing trend(0.4407,0.98×10^(–6)mm^(−3)N^(−1)m^(−1)).

关键词： Selective laser melting H13 steel Solution aging Double aging Friction and wear Retained austenite

A comparative study of surface characterization and corrosion behavior of micro-arc oxidation treated Ti-6Al-4V alloy prepared by SEBM and SLM

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Journal of Iron and Steel Research(International) 2023年第1期30卷 165-175页

作者： Qing-bo Yan Tong Xue shi-feng liu Wan-lin Wang Yan Wang Xi Song Xin Yang Wei-wei Shang Xi’an University of Architecture and Technology Xi’an 710055ShaanxiChina School of Metallurgical and Engineering Xi’an University of Architecture and TechnologyXi’an 710055ShaanxiChina School of Materials Science and Engineering Xi’an University of TechnologyXi’an 710048ShaanxiChina Shaanxi Steel Group Industrial Innovation Research Institute Co. Ltd.Hanzhong 723000ShaanxiChina

Additively manufactured Ti-6Al-4V(TC4)parts have been successfully employed as artificial implants in dental and orthopedic surgery due to their excellent mechanical properties.However,the suboptimal corrosion resistance limits their applications.The surface characterization and corrosion behavior of micro-arc oxidation(MAO)treated TC4 alloy prepared by selective electron beam melting(SEBM)and selective laser melting(SLM)technologies were compared.The corrosion resistance mechanism of SLM-MAO and SEBM-MAO was clarified through the analysis of the microstructure evolution,surface morphology,and electrochemical experiments.The results show that the anatase-type TiO_(2) is partially transformed into the slankite phase after MAO treatment.The surface roughness of SEBM sample was reduced by MAO coating,while the surface roughness of SLM sample increased after MAO,which is related to the difference between the microstructure of the deposited samples caused by different additive manufacturing technologies.When MAO time was 15 min,SLM-MAO and SEBM-MAO coating displayed the best and the worst corrosion resistance,respectively.

关键词： TC4 alloy Selective laser melting Selective electron beam melting Micro-arc oxidation Corrosion resistance

Quasi-In-Situ EBSD Observation of the Orientation Evolution in Polycrystalline Tantalum During Rolling Deformation

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Acta Metallurgica Sinica(English Letters) 2019年第8期32卷 1015-1020页

作者： Ya-Hui liu shi-feng liu Chao Deng Hai-Yang Fan Qing liu College of Materials Science and Engineering Chongqing UniversityChongqing 400044China Electron Microscopy Center of Chongqing University Chongqing UniversityChongqing 400044China Department of Mechanical Engineering KU LeuvenLeuvenBelgium

The evolution of crystallographic orientation of polycrystalline tantalum(Ta)during rolling was characterized by electron backscatter diffraction technique in a quasi-in-situ way,and the microstructure and microtexture before and after the deformation were characterized and analyzed,respectively.In the specimen,164 individual grains were exacted singly from the testing region and their corresponding orientations were reconstructed and analyzed,respectively.Results show that the heterogeneous deformation in a grain can be reflected by the accidented surface microstructure.Moreover,the orientations close to{111}orientations came closer to the{111}corner,while the orientation evolution is more complicated for the orientations close{100}corner,indicating that the evolution of these orientations close to{100}corner seemed to be irregular.

关键词： Tantalum Orientation Quasi-in-situ Rolling

Effect of hydrogen addition on compression deformation behaviour of Ti-0.3Mo-0.8Ni alloy argon-arc welded joints

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Journal of Iron and Steel Research(International) 2021年第5期28卷 621-628页

作者： Zhao-hui Zhang Quan-ming liu Li Fu Hai-ying Yang shi-feng liu School of Metallurgical Engineering Xi'an University of Architecture and TechnologyXi'an 710055ShaanxiChina Shaanxi Key Laboratory of Friction Welding Technologies State Key Laboratory of Solidification ProcessingNorthwestern Polytechnical UniversityXi'an 710072ShaanxiChina Institute of Titanium Alloy Research Northwest Institute for Nonferrous Metal ResearchXi'an 710016ShaanxiChina

The effect of hydrogen addition on compression deformation behaviour of Ti-0.3Mo-0.8Ni alloy argon-arc welded joint has been investigated.Evolution mechanism of hydrogen-induced flow stress was discussed in detail.The results show that with increasing hydrogen content,the stretching and bending extent of fully lamellar microstructures including ot lamellas and acicular hydride continued to increase,the morphology of dynamic recrystallization(DRX)grains tended to change from approximately equiaxed to large lamellar shape,and the quantity of DRX grains and recrystallization degree of grains increased obviously.A large number of dislocations concentrated in the vicinity of the hydride.Steady stress was decreased continuously with increasing hydrogen content,while peak stress of the hydrogenated 0.12 wt.% H weld zone was decreased to the minimum value and then increased slowly.A slight decrease in flow stress of the hydrogenated 0.05 wt.% H weld zone was caused by limited increase in the volume fraction of softer βphase.Hydrogen-induced DRX of a phase and improved dislocation movement by strong interaction between the hydride and dislocation directly resulted in a sharp drop in flow stress of the hydrogenated 0.12 and 0.21 wt.% H weld zone.Solute hydrogen also finitely contributed to a sharp drop in flow stress of the hydrogenated 0.12 and 0.21 wt.% H weld zone by promoted local softening,which induced continuous DRX and more movable dislocations to participate in slipping or climbing.The reinforcement effect and plastic deformation of the hydride and solution strengthening of P phase induced by solute hydrogen finally led to the increase in flow stress of the hydrogenated 0.21 wt.% H weld zone in its true strain range from 0 to 0.36.

关键词： Titanium alloy Welded joint Hydrogen addition Compression behaviour Flow stress Evolution mechanism

Heat transfer performance of porous titanium

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Journal of Iron and Steel Research(International) 2017年第5期24卷 556-560页

作者： shi-feng liu An Li Yao-jia Ren Dong-feng Li Zhao-hui Zhang School of Metallurgical Engineering Xi'an University of Architecture and Technology State Key Laboratory of Powder Metallurgy Central South University

Porous titanium fibre materials with different structural parameters were prepared by vacu- um sintering method. The thickness, porosity and wire diameter of prepared materials were investigated to understand the effects of structural parameters on pool heat transmission performance of titanium fibre porous material. As a result, better heat transfer performance is obtained when overheating is less than 10 ℃. In addition, when the wire diameter is smal- ler, the heat transfer is better. However, when superheating is above 10 ℃, heat transfer performance can be improved by increasing the wire diameter. Moreover, thickness influ- ences the superficial area of the prepared material and affects the thermal resistance when bubbles move inside the material; superficial area and thermal resistance are the two key factors that jointly impact the heat transfer in relation to the thickness of the materials. Ex- perimental results also show that the materials of 3 mm in thickness exhibit the best per formance for heat transmission. Furthermore, changes in porosity affect the nucleation site density and the resistance to bubble detachment; however, the nucleation site density and the resistance to bubble detachment conflict with each other. In summary, the titanium fi- bre porous material with a 50% porosity exhibits suitable heat transfer performance.

关键词： Titanium fibre Porous material Vacuum sintering Pool boiling Heat transfer

Revealing substructure in clock-rolled Ta aided with triple focused ion beam

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Rare Metals 2017年第4期36卷 284-288页

作者： shi-feng liu Xiao-Bo Hao Chao Deng Hai-Yang Fan Qing liu College of Materials Science and Engineering Chongqing UniversityChongqing 400044China

Clock rolling was developed to make defor- mation microstructure homogenize in high-purity Ta. The substructure of deformed Ta was revealed by electron back-scatter diffraction （EBSD） technique aided with triple focused ion beam （FIB）. The results indicate that the triple FIB method can produce a mirror surface required by EBSD analysis. The clock rolling works well for the homogenization of deformed microstructure. Particularly, the local stored energy in { 111 } orientated grains is largely reduced by clock rolling, whereas it is enhanced in {100} orientated grains because of the occurrence of grain subdivision.

关键词： Deformation Substructure Strain pathchange Dislocation boundary Focused ion beam

Through-thickness texture gradient of tantalum sputtering target

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Rare Metals 2017年第6期36卷 523-526页

作者： Chao Deng shi-feng liu Xiao-Bo Hao Jing-Li Ji Qing liu Hai-Yang Fan College of Materials Science and Engineering Chongqing University Chongqing 400044 China

For sputtering targets, through-thickness texture is critical for assuring reliable sputtering performance.In this paper, through-thickness texture gradient of a rolled and subsequently annealed tantalum sputtering target was investigated. The results show that by carefully controlling the rolling process, shear-related components at the surface of the rolled sample could be avoided. Both the rolled sample and the annealed target develop a through-thickness texture gradient with the formation of a stronger {1 1 1}fiber in the center layer compared with that in the surface layer.

关键词： Recrystallization Texture Tantalumsputtering target Electron backscatter diffraction

Sintering Behavior of Porous Titanium Fiber Materials

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Journal of Iron and Steel Research(International) 2014年第9期21卷 849-854页

作者： shi-feng liu Zheng-ping XI Hui-ping TANG Xin YANG Zhao-hui ZHANG Quan-ming liu School of Metallurgical Engineering Xi'an University of Architecture and Technology State Key Laboratory of Porous Metals Materials Northwest Institute for Nonferrous Metal Research Xi'an University of Technology

The porous titanium fiber materials with open porosity were successfully prepared by the vacuum sintering technology. The morphology characteristics of sintering neck of porous titanium fiber materials were investigated by scanning electron microscopy （SEM）. The results show that the formation and growth of sintering neck of porous ti- tanium fiber material approximately follow the rule that the primary mechanism is grain boundary diffusion and sub- sidiary mechanisms are other diffusion mechanisms during the sintering process. The formation and growth of the sintering neck depend mainly on the sintering temperature and slightly on the soaking time. The sintering system of porous titanium fiber material was determined and the equation of the sintering neck＇s length was established.

关键词： porous titanium fiber material sintering temperature sintering neck

Compressive Behavior of Porous Titanium Fiber Materials

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Journal of Iron and Steel Research(International) 2014年第8期21卷 793-796页

作者： shi-feng liu Zheng-ping XI Hui-ping TANG Xin YANG Zhao-hui ZHANG School of Metallurgical Engineering Xi'an University of Architecture and Technology State Key Laboratory of Porous Metals Materials Northwest Institute for Nonferrous Metal Research Xi'an University of Technology

Porous titanium fiber materials with the fiber sizes of 70--120 μm in diameter were prepared by vacuum sintering technology. The morphology and compressive properties of porous titanium fiber materials were investigated by using a scanning electron microscope （SEM） and an MST 858 compression testing machine in quasi-static condition. The results show that porous titanium fibers form complex micro-networks. The stress-strain curves of por- ous titanium fiber materials exhibit elastic region, platform region and densification region and no collapse during platform region. The yield strength of porous titanium fiber materials decreases with increasing the porosity and increasing the fiber diameter.

关键词： porous titanium fiber material compressive behavior energy absorption porosity