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Toward an understanding of dwell fatigue damage mechanism of bimodal Ti-6Al-4V alloys

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Journal of materials Science & Technology 2022年第13期108卷 244-255页

作者： L.R.Zeng L.m.lei X.m.Luo G.P.Zhang Shenyang National Laboratory for materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of mechanical Engineering Chengdu UniversityChengdu 610106China AECC Shanghai Commercial Aircraft Engine manufacturing Co. Ltd.Shanghai 201306China

Dwell fatigue effect is a long-standing problem threatening the long-term service reliability for fan blades and fan disks of an aircraft *** understand the basic mechanism of dwell fatigue damage,pure fatigue and 60 s dwell fatigue properties of bimodal Ti-6Al-4V alloys with different volume fractions of the primaryα(α_(p))phase were examined *** results showed that both pure fatigue and dwell fatigue life decreased with increasing the volume fraction of theα_(p)phase and the dwell fatigue life was lower than the pure fatigue *** quasi-in-situ test results and the quantitative characterization of damage behaviors of the local microstructure units defined by theα_(p)-secondaryα(α_(s))combination reveal that theα_(s)phase close to theα_(p)phase with extensively slip activities was gradually damaged under dwell fatigue loading,while that under pure fatigue loading was undamaged,demonstrating that the dwell loading induced the damage of theα_(s)phase,and further reduced the fatigue life.A stress relaxation-based model is proposed to describe the physical mechanism on dwell fatigue damage of the bimodal Ti-6Al-4V alloy,*** elastic deformation of theα_(s)phase caused by the strain incompatibility would be gradually transformed into plastic deformation during the dwell stage,and thus promotes fatigue *** model provides new insights into the microscopic process of stress/strain transfer between the soft and hard microstructure units under dwell fatigue loading.

关键词： Dwell effect Fatigue damage Stress relaxation Volume fraction of primaryαphase Quasi-in-situ testing

microstructure Dependent Fatigue Cracking Resistance of Ti-6.5Al-3.5mo-1.5Zr-0.3Si Alloy

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Journal of materials Science & Technology 2012年第7期28卷 614-621页

作者： Z.m. Song L.m. lei B. Zhang X. Huang G.R Zhang Shenyang National Laboratory for materials Science Institute of Metal Research Chinese Academy of SciencesShenyang 110016 China AVIC Commercial Aircraft Engine Co. Ltd. Shanghai 200241 China Titanium Alloys Laboratory Beijing Institute of Aeronautical Materials Beijing 100095 China Key Laboratory for Anisotropy and Texture of materials of ministry of Education School of Materials and MetallurgyNortheastern University Shenyang 110819 China

Fatigue cracking behavior from a notch was investigated at room temperature for ***-3.5mo-1.5Zr- 0.3Si （TClI） alloys with four different microstructures obtained at different cooling rates from the β transus temperature. It was found that the alloy with lamellar structures consisting of α/β lamellae or acicular α＇ martensite laths had a higher fatigue crack initiation threshold from the notch, while the bimodal structure with coarse a grain had a lower fatigue cracking resistance. The alloy with α/β lamellar structure showed a higher fatigue crack growth resistance. The length scales of the microstructures were characterized to correlate with fatigue cracking behavior. Fatigue cracking mechanism related to microstructures was discussed.

关键词： Ti alloy Fatigue crack initiation Crack propagation microstructure

Geometrical Scale-Sensitive Fatigue Properties of Ti-6.5Al-3.5mo-1.5Zr-0.3Si Alloys With α/β Lamellar microstructures

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Journal of materials Science & Technology 2014年第12期30卷 1284-1288页

作者： B.Zhang Z.m.Song L.m.lei L.Kang G.P.Zhang Key Laboratory for Anisotropy and Texture of materials Ministry of Education Northeastern University Shenyang National Laboratory for materials Science Institute of Metal Research Chinese Academy of Sciences AVIC Commercial Aircraft Engine Co. Ltd.

Fatigue properties of the Ti-6.5Al-3.5mo-1.5Zr-0.3Si alloy sheets containing different numbers of α/β Widmansttten colonies in the thickness direction of the sheets were investigated by tensionetension fatigue testing. It is found that fatigue properties of the Ti alloy either in low- or high-stress amplitude regimes become more sensitive to the sheet thickness of the Ti alloy as the sheet thickness is comparable to the length scale of the Widmansttten colonies. The basic mechanism of such length scale-sensitive fatigue properties in the Ti alloy was elucidated.

关键词： Fatigue Ti alloy microstructure Size effect

Toward developing Ti alloys with high fatigue crack growth resistance by additive manufacturing

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Journal of materials Science & Technology 2023年第1期132卷 166-178页

作者： F.Wang L.m.lei X.Fu L.Shi X.m.Luo Z.m.Song G.P.Zhang Shenyang National Laboratory for materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China AECC Commercial Aircraft Engine Co. Ltd.Shanghai 201306China

Fatigue crack growth behaviors were investigated by three-point bending tests for TA19 alloy fabricated by laser metal deposition and four kinds of heat-treated *** crack growth resistance of the TA19 samples in the near-threshold regime and Paris regime was evaluated through the experimental characterization and theoretical analysis of the interaction between fatigue crack andα/βphase inter-face,columnar prior-βgrain boundary and colony *** results show that in the near-threshold regime,the fatigue crack propagation threshold and resistance increase with the increase of widths of lamellarαp phases and colonies,and the decrease of the number ofαlaths with an angle(ϕ)relative to the applied stress direction ranging from 75°to 90°.In the Paris regime,the fatigue cracking path can be deflected at colony boundaries or columnar prior-βgrain *** larger the deflection angle,the more tortuous the cracking path and the lower the fatigue crack growth *** angle(γ)of the columnar prior-βgrain growth direction relative to the build direction affects not onlyϕof differentαvariants,but also the fatigue cracking path deflection angle(θij)at columnar prior-βgrain *** optimal combination ofγ=0°-15°-0°-15°for several adjacent columnar prior-βgrains is derived from the theoretical analysis,and that can effectively avoidϕbeing in the range from 75°to 90°and makeθij as large as *** findings provide a guide for the selection of scanning strategies and process parameters to additively manufacture Ti alloys with high fatigue damage tolerance.

关键词： Ti alloy Fatigue crack growth Additive manufacturing Phase interface Grain boundary

On Temperature and Strain Rate Dependent Strain Localization Behavior in Ti-6.5Al-3.5mo-1.5Zr-0.3Si Alloy

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Journal of materials Science & Technology 2013年第3期29卷 273-278页

作者： B.Zhang L.m.lei X.L.Jiang Z.m.Song X.Huang G.P.Zhang Key Laboratory for Anisotropy and Texture of materials(ministry of Education) Northeastern University Titanium Alloys Laboratory Beijing Institute of Aeronautical Materials AVIC commercial Aircraft Engine Co. Ltd. Shenyang National Laboratory for materials Science Institute of Metal ResearchChinese Academy of Sciences

Deformation behaviors of Ti-6.5Al-3.5mo-1.5Zr-0.3Si alloys with α/β lamellar structure were investigated systematically at different temperatures from room temperature to 950 ~C and different strain rates. Results reveal that when the deformation temperature is higher than a critical temperature of 600℃, an evident transition of deformation behavior from localized shear banding to α/β lamella kinking, flow softening and temperature/strain rate-dependent peak flow stress occurred in the alloy. The critical conditions for the occurrence of internal cracking and strain localization behavior associated with temperature and strain rate were determined.

关键词： Titanium alloy Hot working Temperature Strain rate Shear band

Influence of alloy element partitioning on strength of primary α phase in Ti-6Al-4V alloy

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Journal of materials Science & Technology 2018年第5期34卷 782-787页

作者： L.R.Zeng H.L.Chen X.Li L.m.lei G.P.Zhang Shenyang National Laboratory for materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China University of Chinese Academy of Sciences Beijing 100049 China School of materials Science and Engineering University of Science and Technology of China Shenyang 110016 China AVIC Commercial Aircraft Engine Co.LTD Shanghai 200241 China

The partitioning effect of Al（α-phase stabilizer） and V elements（β-phase stabilizer） on strength of the primary α phases in the α/β Ti-6 Al-4 V alloy with the bimodal microstructure was *** was found that partitioning of Al and V elements took place in the Ti-6 Al-4 V alloy during the recrystallization process,leading to the variation of the content of Al and V elements in the primary α phases with changing the volume fraction of the primary α *** tests reveal a general trend that the strength of the primary α phases increases with decreasing the volume fraction of the primary α phases,and such trend is independent on the loading direction relative to the c-axis of the α *** enhanced strength is attributed to the increase of the content of Al element in the primary α phase,but it is not dominated evidently by the change of the V *** solid solution strengthening contributed from both the elastic strain introduced by the solute atoms and the variation of the density of states was estimated theoretically.

关键词： Ti-6Al-4V Nanoindentation Strength Alloy element partitioning Crystallographic orientation

mATHEmATICAL AND PHYSICAL mODELING OF INTERFACIALPHENOmENA IN CONTINOUS CASTING mOULD WITH ARGONINJECTION THROUGH SUBmERGED ENTRV NOZZLE

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Acta metallurgica Sinica(English Letters) 2000年第5期13卷 1079-1086页

作者： H. lei, m. Y. Zhu and J.C. He (School of materials and metallurgy, Northeastern University, Shenyang 110006, China) Sch. of mat. and metall. Northeastern Univ. Shenyang 110006 China

The study on the fluid flow, meniscus oscillation, slag entrapment in continuous casting mould was conducted mathematically and experimentally. The results show that the injection of argon into submerged nozzle enhances the meniscus oscillation, thus increases the probability of slag entrapment, and the critical argon blowing flow rate, which will give rise to slag entrapment, is around 10l/min. The trajectory of bubble is affected by the bubble diameter and the molten steel flow, and the bubble diameter is dominant. The bubble with diameter 1.4mm floats fastest with 0.47m/s terminal velocity.

关键词： continuous casting mould argon injection meniscus oscillation slag entrapment mathematical and physical model

Laser additive manufacturing of strong and ductile Al-12Si alloy under static magnetic field

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Journal of materials Science & Technology 2023年第32期163卷 101-112页

作者： R.Wang J.Wang L.m.lei S.Yu T.Hu S.S.Shuai S.Z.Xu Z.H.Cao X.P.Li C.Y.Chen Z.m.Ren State Key Laboratory of Advanced Special Steels School of Materials Science and EngineeringShanghai UniversityShanghai 200444China AECC Commercial Aircraft Engine Co. Ltd.Shanghai 201108China School of mechanical and manufacturing Engineering The University of New South Wales(UNSW Sydney)Sydney NSW 2052Australia

Rapid cooling and solidification during laser additive manufacturing(LAm)can produce ultra-fine microstructure with higher ***,the non-uniform cell/grain structure can easily result in early stress concentration and fracture during deformation,which remains a major challenge for the LAm *** Al-12Si as the model alloy,we employed the external static magnetic field(SmF)to modulate the laser powder bed fusion process(L-PBF),demonstrating a uniform microstructure with a refined cell *** mechanical properties show that the SmF can produce a combination of high tensile strength of 451.4±0.5 mPa and large uniform elongation of 10.4%±0.79%,which are superior to those of previously-reported Al-Si alloys with post-treatment or element *** mechanism analysis based on multi-scale simulation reveals the determining role of SmF in rapid solidification,and this method is applicable to the microstructure control of other metallic materials during LAm.

关键词： Laser powder bed fusion magnetic field Al alloys Grain refinement Strengthening mechanism

Toward qualification of additively manufactured metal parts:Tensile and fatigue properties of selective laser melted Inconel 718 evaluated using miniature specimens

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Journal of materials Science & Technology 2022年第2期97卷 239-253页

作者： H.Y.Wan W.K.Yang L.Y.Wang Z.J.Zhou C.P.Li G.F.Chen L.m.lei G.P.Zhang Shenyang National Laboratory for materials Science Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China School of materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China materials&manufacturing Qualification Group Corporate TechnologySiemens Ltd.Beijing 100102China AECC Shanghai Commercial Aircraft Engine manufacturing Co. LtdShanghai 201306China

Combined with the topology optimization,additive manufacturing can be used to fabricate metal parts with complex ***,due to the geometrical variations and microstructure heterogeneities of the additively manufactured metal parts,new standards with the use of miniature specimens are required for the evalutation of the spatial distribution of mechanical properties throughout the ***,we conduct a systematic investigation on tensile and fatigue properties of selective laser melted Inconel718 specimens with different thicknesses ranging from 0.1 mm to 1 mm.A“microstructure unit”that can well reflect the microstructure characteristic of selective laser melted materials is *** results reveal that premature necking with a dramatic drop in uniform elongation occurs if the ratio(t/d)of specimen thickness(t)to the"microstructure unit"size(d)is less than *** necking is mainly attributed to the transition of strain localization *** also propose a probabilistic statistical model for fatigue limit prediction based on the available fatigue *** is recommended that the criterion of t/d≥4 should be satisfied to ensure that the yield strength,the uniform elongation,and the fatigue limit determined by the miniature specimens are comparable with those determined by standard *** findings may provdie a guide to the establishment of miniature specimen-based standards toward the qualification of additively manufactured metal parts.

关键词： Selective laser melting Inconel 718 miniature specimen microstructure unit Thickness effect