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Investigation on Strengthening Mechanism of China Low-Activation Ferrite Steel upon thermo-mechanical treatment

Acta Metallurgica Sinica(English Letters) 2024年第2期37卷 373-387页

作者： Dongtian Yang Liangyin Xiong Hongbin Liao Guoping Yang Xiaoyu Wang Shi Liu Institute of Metal Research Chinese Academy of SciencesShenyang110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang110016China Center for Fusion Science Southwestern Institute of PhysicsChengdu610041China

The objective of this study was to investigate the influence of strengthening mechanisms on the high-temperature mechanical properties of China low-activation ferrite(CLF-1)steel,which underwent thermodynamic design and thermo-mechanical treatment(TMT).The microstructure characterization in the normalized and tempered condition and the TMT condition was carried out using optical microscopy,X-ray diffractometer,and scanning electron microscopy with electron backscatter diffraction.High-resolution transmission electron microscopy was employed to determine the crystallographic structures of precipitated phases.The results indicated that the addition of Ti led to an increase in the allocation of C in MC phase and an enhancement in the content of MC phase.Compared to CLF-P steel in the normalized and tempered condition,a 1.5-fold increase in dislocation density and an order of magnitude improvement in MX phase density were achieved after TMT.The formation of high-density nano-scale MC phases during TMT played a significant role in precipitation strengthening due to their favorable coherent relationship with the matrix and low interfacial free energy.The excellent high-temperature mechanical properties observed in CLF-P steel after TMT can be attributed to the combined effects of precipitation strengthening,dislocation strengthening,and lath strengthening.

关键词： China low-activation ferrite(CLF-1)steel thermo-mechanical treatment MC phase Crystallographic structure Strengthening mechanism

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Improved Properties in Relation to Fine Precipitate Microstructures Tailored by Combinatorial Processes in an Al-Cu-Mg-Si Alloy

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Acta Metallurgica Sinica(English Letters) 2020年第11期33卷 1527-1534页

作者： Fengjiao Niu Jianghua Chen Cuilan Wu Jing Wu Xiandong Xu Pan Xie Xiongwei Yu Center for High-Resolution Electron Microscopy College of Materials Science and EngineeringHunan UniversityChangsha 410082China

The 2xxx series Al alloys have been widely used in aerospace industry owing to their high strength,good plasticity and superior formability.To ensure a good control of shape,the quenched alloy sheets require a small pre-deformation before artificial aging.However,this pre-deformation considerably deteriorates the mechanical strength of the Al-3.0 Cu-1.8 Mg-0.5 Si(wt%)alloys due to the formation of unfavorable large-sized precipitates at dislocations.To tackle this issue,we designed a pre-aging process prior to the pre-deformation.The thermal-mechanical treatment,involving pre-aging,pre-deformation and subsequent aging,markedly enhanced the ultimate tensile strength up to 521 MPa compared to that(448 MPa)of the alloy without pre-aging.Microstructure characterization revealed that the fine precipitates(~2 nm)with a uniform dispersion were promoted within the Al matrix,which in turn partly suppressed the formation of the unfavorable large-sized precipitate(~100 nm).Our findings provide a new clue for designing stronger Al alloys with age-hardenability.

关键词： Aluminum alloys thermo-mechanical treatment Precipitation Age-hardenability

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Formation of Nano/Ultrafine Grains in AISI 321 Stainless Steel Using Advanced thermo-mechanical Process

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Acta Metallurgica Sinica(English Letters) 2015年第4期28卷 499-504页

作者： Mohsen Golzar Shahri S.Rahman Hosseini Mehdi Salehi Department of Materials Engineering Isfahan University of Technology Department of Materials Engineering Maleke-Ashtar University of Technology

Production of nano/ultrafine grains through deformation-induced martensite formation and its reversion to austenite in an AISI 321 stainless steel was studied. The repetitive cold rolling and subsequent annealing were conducted to obtain nanocrystalline structure. Heavy cold rolling （90% reduction） at ＋20 and -20 ℃ was carded out to induce the formation of α′-martensite from metastable austenitic material. The process was followed by annealing treatment at 700-900 ℃ for 0.5-30 min. Effects of process parameters, i.e., ＂reduction percentage,＂＂rolling temperature,＂＂annealing temperature＂ and ＂annealing time＂, on the microstructural development were considered. Microstructural evolutions were conducted using feritscope, X-ray diffractometer and scanning electron microscope. Hardness of the specimens was measured by Vickers method. Results revealed that the higher thickness reduction and lower rolling temperature provided more martensite volume fraction and further hardness. X-ray diffraction patterns and feritoscopic results indicated that saturated strain （εs） was reduced from 2.3 to 0.9 when temperature declined from ＋20 to -20 ℃. The smallest grain size （about 70 nm） was achieved in the condition of cold rolling at -20℃followed by annealing at 750 ℃for 5 min.

关键词： Austenitic stainless steel Deformation-induced martensite Nano/ultrafine grain structure thermo-mechanical treatment

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thermomechanical Processing and Superplasticity of AZ91 Magnesium Alloy

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Journal of Materials Science & Technology 2004年第3期20卷 295-297页

作者： RongshiCHEN J.J.Blandin M.Suéry QudongWANG EnhouHAN StateKeyLabforCorrosionandProtection InstituteofMetalResearchChineseAcademyofSciencesShenyang110016China InstitutNationalPolytechniquedeGrenoble(INPG)GéniePhysiqueetMécaniquedesMatériaux(GPM2) UMRCNRS5010ENSPGBP4638402Saint-Martind'HéresCedexFrance SchoolofMaterialsScience&Engineering NationalResearchCenterofLightAlloyNetFormingEngineeringShanghaiJiaoTongUniversityShanghai200030China

The effect of extrusion on grain refinement has been studied in the AZ91 cast ingots. It is found that grain sizesmaller than 10μm can be obtained by the extrusion processing. Vickers hardness measurements were also carriedout to evaluate the effect of these processes on the room temperature mechanical properties. The experimentalresults of high temperature tensile tests revealed that the stress was inversely proportional to the square of the grainsize and that the activation energy for superplastic flow was higher than that for grain boundary diffusion.

关键词： Magnesium alloy thermo-mechanical treatment Superplasticity mechanical properties

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mechanical Characterisation of Densified Hardwood with Regard to Structural Applications

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Journal of Renewable Materials 2020年第9期8卷 1091-1109页

作者： Katharina Müller Walter Sonderegger Oliver Kläusler Michael Klippel Edwin Zea Escamilla Institute of Structural Engineering(IBK) Chair of Structural Engineering–Timber StructuresSwiss Federal Institute of Technology ZurichZurich8093Switzerland Swiss Wood Solutions AG 8600 DübendorfSwitzerlandPreviously at Institute for Building Materials(IfB)Chair of Wood Materials ScienceSwiss Federal Institute of Technology ZurichZurich8093Switzerland College of Civil Engineering Nanjing Forestry UniversityNanjing210037China Sustainable Building Center for Corporate Responsibility and SustainabilityUniversity of ZurichZurich8001Switzerland

The demand for high-performance,yet eco-friendly materials is increasing on all scales from small applications in the car industry,instrument or furniture manufacturing to greater dimensions like floorings,balcony furnishings and even construction.Wood offers a good choice on all of these scales and can be modified and improved in many different ways.In this study,two common European hardwood species,Beech(Fagus sylvatica L.)and Ash(Fraxinus excelsior L.)were densified in radial direction by thermo-mechanical treatment and the densified product was investigated in an extensive characterisation series to determine all relevant mechanical properties.Compression in the three main directions(longitudinal,tangential,radial)and tension perpendicular to the grain(tangential,radial)were tested and compared to reference specimens with native density.Strength and modulus of elasticity were determined in all tests.In addition,a Life Cycle Assessment was carried out to evaluate the environmental impact associated to the densification process.The experimental investigations showed that strength and stiffness of hardwood in the longitudinal and tangential directions improve significantly by radial densification,whereas some properties in the radial direction decrease.The Life Cycle Assessment showed that artificial wood drying has higher impact than wood densification.Furthermore,the transport distance of the raw material highly influences the environmental impact of the final densified product.The paper then also offers an overview of possible applications in structural timber construction.Densified hardwood is a viable option as local reinforcement,where high compressive or tensile strength is needed.The wood densification process offers an alternative to the use of carbon-intense steel components or hardwoods from tropical forests.

关键词： Hardwood densification high-performance construction materials thermo-mechanical treatment mechanical characterisation life cycle assessment timber structures

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mechanical Properties Optimization Metal Bars and Sheets Made of 34CrNiMo6 Steel

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Journal of Iron and Steel Research(International) 2011年第S1期18卷 956-960页

作者： Dzugan Jan Novy Zbysek Motycka Petr Martinkova Jana Martinek Petr COMTES FHT Inc. Prumyslova 995334 41 DobranyCzech Republic

Currently available and well known materials treated by a special procedures can provide superior properties in the comparison to presently obtained ones.Special treatment procedures are efficiently developed with the use of physical simulators nowadays.Physical simulators allow treatment optimization on small scale laboratory samples which can be subsequently transferred to real production processes later on.Nevertheless,there is always need of successful transfer from small scale laboratory experiments to real production of for example metal sheets.In the current paper thermo-mechanical procedure developed for 34CrNiMo6 steel under laboratory conditions is applied to metal sheets production.There were obtained very promising properties on the bulk material samples processed in the physical simulator,the challenge was to obtain similar properties on a real metal sheets by a transfer of laboratory procedure to metal sheet production process.In the considered case the combination of tensile strength and elongation were especially required for considered application in a train body.In order to achieve excellent elongation for high strength hardened steel,very fine microstructure has to be attained through the thermo-mechanical process optimization.Very good results were achieved on produced metal sheets.6% elongation was attained allowing the possibility of further material processing,e.***.bending of sheets,with tensile strength exceeding 1500 MPa.The study presented here confirms usefulness of thermo-mechanical simulators for new procedures development.With the use of the simulator of thermaldeformation cycles a materials with optimized properties for certain application can be efficiently developed.

关键词： physical simulation thermo-mechanical treatment

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β Stability and mechanical Behavior of Metastable Type TiNb Based Alloys

β Stability and Mechanical Behavior of Metastable Type TiNb...

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中国材料大会2012

作者： Guangyue Liao Shun Guo Zhenzhen Bao Xinqing Zhao School of materials science and engineering Beihang University

Metastable type TiNb based alloys of Ti-35Nb, Ti-35Nb-4Sn and Ti-42Nb-4Sn （wt. %） with different stability were prepared and thermo-mechanical treatment was carried out to investigate their microstructural evolution and mechanical properties. It was found that although the TiNb based alloy with lower stability performs lower strength in its solution state due to the stress induced martensitic transformation, they could be strengthened significantly by severe cold rolling followed by aging, remaining a relative low elastic modulus. X-ray diffraction, transmission electron microscopy and mechanical test were conducted to characterize the microstructural evolution and mechanical behavior of the metastable β type TiNb based alloys with different β stability. The strengthening mechanism was discussed on the basis of the cold deformation and martensitic transformation.

关键词： β Ti alloy Ti-Nb-Sn thermo-mechanical treatment Martensitic transformation.

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