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Microstructure evolution and strengthening mechanism of high -performance powder metallurgy TA15 Titanium alloy by hot rolling

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International Journal of Minerals,Metallurgy and Materials 2024年第6期31卷 1426-1436页

作者： Ying Gao Ce Zhang Jiazhen Zhang Xin Lu Beijing Advanced Innovation Center for Materials Genome Engineering State Key Laboratory for Advanced Metals and MaterialsInstitute for Advanced Ma-terials and TechnologyUniversity of Science and Technology BeijingBeijing 100083China National Engineering Research Center for Advanced Rolling Technology National Engineering Research Center for Flat Rolling EquipmentInstitute of Engin-eering TechnologyUniversity of Science and Technology BeijingBeijing 100083China

Hot deformation of sintered billets by powder metallurgy(PM)is an effective preparation technique for Titanium alloys,which is more significant for high-alloying alloys.In this study,Ti–6.5Al–2Zr–Mo–V(TA15)Titanium alloy plates were prepared by cold press-ing sintering combined with high-temperature hot rolling.The microstructure and mechanical properties under different process paramet-ers were investigated.Optical microscope,electron backscatter diffraction,and others were applied to characterize the microstructure evolution and mechanical properties strengthening mechanism.The results showed that the chemical compositions were uniformly dif-fused without segregation during sintering,and the closing of the matrix craters was accelerated by increasing the sintering temperature.The block was hot rolled at 1200℃ with an 80%reduction under only two passes without annealing.The strength and elongation of the plate at 20–25℃ after solution and aging were 1247 MPa and 14.0%,respectively,which were increased by 24.5%and 40.0%,respect-ively,compared with the as-sintered alloy at 1300℃.The microstructure was significantly refined by continuous dynamic recrystalliza-tion,which was completed by the rotation and dislocation absorption of the substructure surrounded by low-angle grain boundaries.After hot rolling combined with heat treatment,the strength and plasticity of PM-TA15 were significantly improved,which resulted from the dense,uniform,and fine recrystallization structure and the synergistic effect of multiple slip systems.

关键词： elemental powder powder metallurgy Titanium alloy hot rolling strength and plasticity

Experimental Study on Titanium alloy Cutting Property and Wear Mechanism with Circular-arc Milling Cutters

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Chinese Journal of Mechanical Engineering 2023年第3期36卷 219-229页

作者： Tao Chen Jiaqiang Liu Gang Liu Hui Xiao Chunhui Li Xianli Liu School of Mechanical and Power Engineering Harbin University of Science and TechnologyHarbin 150080China

Titanium alloy has been applied in the field of aerospace manufacturing for its high specific strength and hardness.Nonetheless,these properties also cause general problems in the machining,such as processing inefficiency,serious wear,poor workpiece face quality,etc.Aiming at the above problems,this paper carried out a comparative experimental study on Titanium alloy milling based on the CAMCand BEMC.The variation law of cutting force and wear morphology of the two tools were obtained,and the wear mechanism and the effect of wear on machining quality were analyzed.The conclusion is that in contrast with BEMC,under the action of cutting thickness thinning mechanism,the force of CAMC was less,and its fluctuation was more stable.The flank wear was uniform and near the cutting edge,and the wear rate was slower.In the early period,the wear mechanism of CAMC was mainly adhesion.Gradually,oxidative wear also occurred with milling.Furthermore,the surface residual height of CAMC was lower.There is no obvious peak and trough accompanied by fewer surface defects.

关键词： Circular-arc milling cutter Titanium alloy Ball-end milling cutter Surface quality Milling force Tool wear Machining quality

Evolution mechanism of lamellarαand interlayeredβduring hot compression of TC21 Titanium alloy with a widmanst?tten structure

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Chinese Journal of Aeronautics 2022年第3期35卷 475-483页

作者： Xiaoyu ZHENG Ke WANG Cheng ZHANG Renlong XIN Qing LIU International Joint Laboratory for Light alloys(MOE) School of Materials Science and EngineeringChongqing UniversityChongqing 400044China

TC21 Titanium alloy,as an important metal to fabricate the aircraft structural components,has attracted great attentions recently.A TC21 Titanium alloy with widmanst?tten structure was isothermally compressed.Based on the microstructure observation,the evolution of initialβgrain,Grain Boundaryαphase(α;),lamellar a and interlayeredβwas systematically investigated.The results showed that,with the increasing of height reduction,theα;underwent an evolution process from bending/kinking to breaking inducing the corresponding blurring of initial coarse b grain outline.Meanwhile,a significant phase transformation from a to b took place at the terminations of brokenα;.The evolution of lamellarαand interlayeredβin the colony was closely related to their deformation compatibility.In the a colony,the interlayered b experienced a larger deformation amount than lamellarα.The higher distortion energy promoted the occurrence of Dynamic Recovery(DRV)and Dynamic Recrystallization(DRX)to generate many Low Angle Boundaries(LABs)and High Angle Boundaries(HABs)in interlayered b,which induced an apparent grain refinement of b phase.On the contrary,the lower distortion energy and low deformation temperature suppressed the occurrence of DRV/DRX and restrained the globularization of lamellarα.Furthermore,the microstructure observation clearly revealed that the shearing separation mechanism dominated the evolution of the a phase from lamellar to short bar-like morphology.

关键词： Globularization Grain refinement Hot deformation Interlayeredβ Lamellarα Titanium alloy

Hierarchical structure and deformation behavior of a novel multicomponent β Titanium alloy with ultrahigh strength

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Journal of Materials Science & Technology 2022年第12期107卷 227-242页

作者： X.Li X.N.Wang K.Liu G.H.Cao M.B.Li Z.S.Zhu S.J.Wu School of Materials Science and Engineering Beihang UniversityBeijing 100191China Titanium alloys Laboratory Beijing Institute of Aeronautical MaterialBeijing 100095China School of Materials Science and Engineering Shanghai UniversityShanghai 200444China

Based on the general [Mo] equivalent criterion and d-electron orbital theory, a new ultrahigh-strength βTitanium alloy with eight major elements(Ti-4.5Al-6.5Mo-2Cr-2.6Nb-2Zr-2Sn-1V, TB17) for industrial applications was developed. An ingot of five tons was successfully melted by thrice vacuum consumable arc melting. The microstructure and elements partitioning of different conditions were investigated systematically. The results suggest that the hierarchical structures of micro-scale first α phase(αf), nano-scale secondary α phase(αs), and ultrafine FCC substructures can be tailored by solution plus aging(STA) heat treatment. The lateral and epitaxial growth of αfphase promotes the HCP-α to FCC substructure transformation with the help of elements partitioning during the aging process. Moreover, the element V, generally regarded as β stabilizer, is found to mainly concentrate in the Al-rich αfphase in this study probably due to its relatively lower content and the strong bonding energy of Al-V. The hierarchical structure has a strong interaction with dislocations, which contributes to achieve a superhigh strength of 1376 MPa.In addition, the plastic strain is partitioned in the multi-scale precipitates(such as the α and FCC substructures) and β matrix, resulting in a considerable plasticity. TEM observation demonstrates that high density entangled dislocations at interfaces and mechanical twins exist in the STA sample after tensile test. It can be deduced that both dislocation slipping and twinning mechanisms are present in this alloy.Therefore, TB17 alloy can serve as an excellent candidate for structural materials on aircrafts that require high strength and lightweight.

关键词： Titanium alloy Hierarchical structure Deformation behavior Ultrahigh strength Elements partitioning

Direct ink writing to fabricate porous acetabular cups from Titanium alloy

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Bio-Design and Manufacturing 2023年第2期6卷 121-135页

作者： Naima Valentin Weijian Hua Ashish K.Kasar Lily Raymond Pradeep L.Menezes Yifei Jin Mechanical Engineering Department University of NevadaRenoRenoNV 89557USA

Acetabular cups,which are among themost important implants in total hip arthroplasty,are usually made from Titanium alloys with high porosity and adequate mechanical properties.The current three-dimensional(3D)printing approaches to fabricate customized acetabular cups have some inherent disadvantages such as high cost and energy consumption,residual thermal stress,and relatively low efficiency.Thus,in this work,a direct ink writing method was developed to print a cup structure at room temperature,followed by multi-step heat treatment to form microscale porous structure within the acetabular cup.Our method is facilitated by the development of a self-supporting titanium-6 aluminum-4 vanadium(Ti64)ink that is composed of Ti64 particles,bentonite yield-stress additive,ultraviolet curable polymer,and photo-initiator.The effects of Ti64 and bentonite concentrations on the rheological properties and printability of inks were systematically investigated.Moreover,the printing conditions,geometrical limitations,and maximum curing depth were explored.Finally,some complex 3D structures,including lattices with different gap distances,honeycomb with a well-defined shape,and an acetabular cup with uniformly distributed micropores,were successfully printed/fabricated to validate the effectiveness of the proposed method.

关键词： Acetabular cup Direct ink writing Titanium alloy Bentonite Heat treatment

Antibacterial copper-bearing Titanium alloy prepared by laser powder b e d fusion for superior mechanical performance

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Journal of Materials Science & Technology 2023年第1期132卷 100-109页

作者： Huan Liu Hai Wang Ling Ren Dong Qiu Ke Yang School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Centre for Additive Manufacturing School of EngineeringRMIT UniversityMelbourneVictoriaAustralia Binzhou Institute of Technology Weiqiao-UCAS Science and Technology ParkBinzhouShandong Province256606China Shandong Key Laboratory of Advanced Aluminium Materials and Technology Weiqiao-UCAS Science and Technology ParkBinzhouShandong Province256606China

Copper element was added in pure titanium to produce a new biomedical titanium-copper alloy by laser powder bed fusion(LPBF).Addition of copper can eliminate the mismatch of high strength but poor duc-tility problem caused by lathα’martensite,which is the usual microstructure of nearαTitanium alloy fabricated by LPBF.Instead of by the usual trade-offrelationship between strength and ductility,which is a long-standing challenge for martensitic Titanium alloys,in this study,we proposed a boundary engineer-ing strategy and aim to synergistically enhance the strength and ductility of martensitic Titanium alloy fabricated by LPBF.It is hypothesized that whilst both low-angle and high-angle grain boundaries are beneficial to the strength,high-angle grain boundary can simultaneously improve the ductility of materi-als.To test this strategy,a Ti-5Cu(wt.%)alloy is selected to compare against pure titanium and Ti-6Al-4V at the same laser processing conditions.EBSD,TEM and XRD analysis show that the as-fabricated LPBF Ti-5Cu alloy is comprised of partially tempered martensite with extraordinarily high number density of both high-angle and low-angle grain boundaries as well as low dislocation density.Such microstructure enables a high tensile strength of 940-1020 MPa,which is at a similar level as LPBF Ti-6Al-4V,and an excellent elongation of 13%-16%,twice as much as that of LPBF Ti-6Al-4V.The mechanism of microstruc-ture refinement in LPBF Ti-5Cu at different levels from prior-βgrains,martensitic packets,blocks to laths is also discussed.

关键词： Titanium alloy Laser powder bed fusion Boundary engineering Martensite Mechanical properties

Grinding Characteristics of MoS_(2)-Coated Brazed CBN Grinding Wheels in Dry Grinding of Titanium alloy

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Chinese Journal of Mechanical Engineering 2023年第4期36卷 43-55页

作者： Junshuai Zhao Biao Zhao Wenfeng Ding Bangfu Wu Ming Han Jiuhua Xu Guoliang Liu National Key Laboratory of Science and Technology on Helicopter Transmission Nanjing University of Aeronautics and AstronauticsNanjing 210016China AECC Zhongchuan Transmission Machinery Co. LtdChangsha 410200China

As an important green manufacturing process,dry grinding has problems such as high grinding temperature and insufficient cooling capacity.Aiming at the problems of sticking and burns in dry grinding of Titanium alloys,grinding performance evaluation of molybdenum disulfide(MoS_(2))solid lubricant coated brazed cubic boron carbide(CBN)grinding wheel(MoS_(2)-coated CBN wheel)in dry grinding Titanium alloys was carried out.The lubrication mechanism of MoS_(2)in the grinding process is analyzed,and the MoS_(2)-coated CBN wheel is prepared.The results show that the MoS_(2)solid lubricant can form a lubricating film on the ground surface and reduce the friction coefficient and grinding force.Within the experimental parameters,normal grinding force decreased by 42.5%,and tangential grinding force decreased by 28.1%.MoS_(2)lubricant can effectively improve the heat dissipation effect of Titanium alloy grinding arc area.Compared with common CBN grinding wheel,MoS_(2)-coated CBN wheel has lower grinding temperature.When the grinding depth reaches 20μm,the grinding temperature decreased by 30.5%.The wear of CBN grains of grinding wheel were analyzed by mathematical statistical method.MoS_(2)lubricating coating can essentially decrease the wear of grains,reduce the adhesion of Titanium alloy chip,prolong the service life of grinding wheel,and help to enhance the surface quality of workpiece.This research provides high-quality and efficient technical support for Titanium alloy grinding.

关键词： Titanium alloy Dry grinding MoS_(2)-coated CBN wheel Grinding wheel wear

Development of Ti-Al-Ta-Nb-(Re)near-αhigh temperature Titanium alloy:Microstructure,thermal stability and mechanical properties

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Journal of Materials Science & Technology 2022年第14期109卷 1-11页

作者： Juan Li Yaqun Xu Wenlong Xiao Chaoli Ma Xu Huang Key Laboratory of Aerospace Advanced Materials and Performance of Ministry of Education School of Materials Science and EngineeringBeihang UniversityBeijing 100191China AECC Beijing Institute Of Aeronautical Materials Beijing 100095China

Mechanical properties and microstructural stability under the service temperature are important to the high temperature Titanium alloy.In order to evaluate the potential in increase the service temperature of Ti alloy,two near-αTi alloys with high content of Al asα-stabilizer and Ta,Nb and/or Re asβ-stabilizers were designed and prepared by ingot metallurgy and thermomechanical processing,and the microstructure and mechanical properties before and after thermal exposure at 650℃ for 100 h were characterized.The results indicated that due to the weakβ-stabilizing ability of Ta and Nb elements,only a small amount ofβphase was formed in Ti-10Al-4Ta-2Nb alloy.With a trace Re addition,theβphase was obviously increased in Ti-10Al-4Ta-2Nb-0.25Re,indicating that the Re was a strongβ-stabilizer.Under the same thermomechanical conditions,the Re addition decreased the volume fraction of primaryα(α_(p))phase and refined the secondaryα(α_(s))phase evidently.The primaryαphase presented an obvious core-shell structure in the Ti-10Al-4Ta-2Nb alloy,with higher Al concentration in the shell.While the core-shell structure was not obvious in the Re-containing alloy due to the Re decreases the diffusion of Al,Ta and Nb elements.A large number of orderedα_(2)precipitates can be observed in theα_(p)andα_(s) phases of two alloys.Theα_(2)precipitates continuously grew up during thermal exposure,however,their growth rate in theα_(s)phase of Re-containing alloy were lower than that of Ti-10Al-4Ta-2Nb alloy.Although plenty of orderedα_(2)precipitates formed in the Ti-10Al-4Ta-2Nb alloy,the alloy had a certain plasticity at room temperature.The trace Re addition evidently increased the tensile strength but caused the decrease of the plasticity.After thermal exposure,the strength was further increased,while the plasticity was decreased for both of alloys.

关键词： Titanium alloy High temperature Microstructure Mechanical properties α_(2)precipitates Thermal exposure

Ordering-induced Elinvar effect over a wide temperature range in a spinodal decomposition Titanium alloy

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Journal of Materials Science & Technology 2023年第19期150卷 245-255页

作者： D.L.Gong H.L.Wang S.H.Hao P.Liu X.Yang Y.N.Jiang W.J.Wang K.Lin B.Li K.Du Y.D.Wang R.Yang Y.L.Hao Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China School of Mechanical Engineering Dongguan University of TechnologyDongguan 523808China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Analysis and Testing Center Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Beijing Advanced Innovation Center for Materials Genome Engineering Institute of Solid State ChemistryDepartment of Physical ChemistryUniversity of Science and Technology BeijingBeijing 100083China State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China

Temperature-independent elastic modulus is termed as Elinvar effect,which is available by tuning the continuous spin transition of ferromagnetic alloys via composition optimization and the first-order martensitic transformation of shape memory alloys via plastic deformation.However,these reversible mechanisms are restricted generally in a narrow temperature range of less than 300 K.Here reports,by tuning a spinodal decomposition in a Ti-Nb-based Titanium alloy via aging treatment,both the Elinvar effect in a wide temperature range of about 500 K and a high strength-to-modulus ratio of about 1.5%can be obtained by a continuous and reversible crystal ordering mechanism.The results demonstrate that the alloy aged at 723 K for 4 h has a nanoscale plate-like modulatedβ+α"two-phase microstructure and its elastic modulus keeps almost constant from 100 to 600 K.Synchrotron and in-situ X-ray diffraction measurements reveal that the crystal ordering parameter of theα"phase increases linearly with temper-ature from 0.88 at 133 K to 0.97 at 523 K but its volume fraction keeps a constant of about 33.8%.This suggests that the continuous ordering of theα"phase toward the high modulusαphase induces a posi-tive modulus-temperature relation to balance the negative relation of the elastically stableβphase.The aged alloy exhibits a high yield strength of 1200 MPa,good ductility of 16%and a high elastic admissible strain of 1.5%.Our results provide a novel strategy to extend the Elinvar temperature range and enhance the strength by tuning the crystal ordering of decomposition alloys.

关键词： Titanium alloy Spinodal decomposition Crystal ordering Elinvar effect Mechanical properties