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Properties and microstructure of copper–titanium alloys with magnesium additions

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Rare Metals 2024年第5期43卷 2290-2299页

作者： Lue Huang Li-Jun Peng Jiang Li Xu-Jun Mi Gang Zhao Guo-Jie Huang Hao-Feng Xie Yi-Cheng Cao Wen-Jing Zhang Zhen Yang State Key Laboratory of Nonferrous Metals and Processes GRINM Group Co. Ltd. GRIMAT Engineering Institute Co. Ltd. School of Materials Science and Engineering Northeastern University General Research Institute for Nonferrous Metals China Academy of Space Technology China Nonferrous Metals Mining Group (Tianjin) Co.Ltd

The volume fractions and morphology of precipitates in precipitation-strengthened Cu-Ti alloys,which precipitate mainly as continuous and discontinuous precipitates,are important for the application of the alloy.This study employed hardness and electrical conductivity tests transmission electron microscopy （TEM）,atom probe tomography （APT）,and first-principles calculations to demonstrate that the addition of Mg is effective for accelerating nanosized continuous β'-Cu4Ti precipitation as well as for suppressing the precipitation of coarse lamellar discontinuous β-Cu4Ti precipitates along the grain boundaries,resulting in Cu-Ti alloys with high yield strength and good electrical conductivity.The results showed that the continuous precipitation of β'-Cu4Ti was accelerated by the Mg additions,which reduced the supersaturation of the matrix,thereby reducing the chemical driving force for the discontinuous precipitates.On the other hand,Mg additions increased the mismatch between the discontinuous β-Cu4Ti precipitates and matrix decreased the nucleation rate of the discontinuous precipitates,and increased the spacing of the discontinuous precipitation layer,resulting in a lower growth rate of the discontinuous precipitates.Therefore,the addition of Mg to Cu-Ti alloys enhances the strength and improves the resistance to over-ageing.

关键词： Cu-Ti-Mg alloy precipitation hardening Discontinuous precipitation Continuous precipitation Microstructure formation mechanism

precipitation hardening OF ELINVAR ALLOY

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Acta Metallurgica Sinica(English Letters) 1991年第1期4卷 33-36页

作者： LIU Zhiguo CHEN Yong CAO Yanni Nanjing University,Nanjing,ChinaZHU Zhengsheng Shaanxi Iron and Steel Institute,Xi’an,China Professor,Dept.of Physics,Nanjing,University,Nanjing 210008,China

The microstructural evolution and precipitation hardening of an Elinvar alloy doped with Ti and Al during isothermal aging at 700℃ have been investigated by atom probe field ion microscopy and microhardness measurements.The γ′ precipiates are spherical and coherent with the matrix.The chemical composition of the precipitates are(Ni_(0.53)Fe_(0.47)_3 (Ti_(0.(?))Al_(0.4)). During aging,a Lifshitz-Wagner type dissolution and coarsening reaction of the precipitates has been observed,The hardness of the material varies with the aging time and reaches maxi- mum when the average diameter of the precipitates was about 11 nm.

关键词： Elinvar alloy atom probe field ion microscope γ-phase precipitation hardening atom probe selected area analysis

Effect of MWCNT reinforcement on the precipitation-hardening behavior of AA2219

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International Journal of Minerals,Metallurgy and Materials 2018年第1期25卷 53-61页

作者： Shijo Thomas Umasankar V. School of Mechanical and Building Sciences VIT University

Aluminum alloy matrix composites have found a predominant place in research, and their applications are explored in almost all industries. The aerospace industry has been using precipitation-hardenable alloys in structural applications. However, insufficient literature is available on the influence of multiwalled carbon nanotubes （MWCNTs） on precipitation-hardenable alloy composite materials; thus, this work was designed to elucidate the effect on MWCNT reinforcement on AA2219 with and without precipitation hardening. Reinforcement with MWCNTs has been reported to accelerate precipitation and to achieve greater hardness within a much shorter time. The addition of 0.75wt% MWCNTs resulted in maximal hardness at 90 min, which is approximately 27% of improvement over the maximum hardness achieved by the corresponding monolithic alloy after 10 h of aging. The sample reinforced with 0.75wt% MWCNTs showed an improve- ment of 82% in hardness by solutionizing and aging compared to that achieved by sintering.

关键词： aluminum metal-matrix composites multi walled carbon nanotubes （MWCNT） powder metallurgy heat treatment precipitation hardening

Evaluation of precipitation hardening in TiC-reinforced Ti_2AlNb-based alloys

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International Journal of Minerals,Metallurgy and Materials 2018年第4期25卷 453-458页

作者： Ya-ran Zhang Qi Cai Yong-chang Liu Zong-qing Ma Chong Li Hui-jun Li State Key Laboratory of Hydraulic Engineering Simulation and Safety School of Materials Science and Engineering Tianjin University Materials Genome Institute Shanghai University

Ti2AlNb-based alloys with 0.0 wt%, 0.6 wt%, and 2.0 wt% carbon nanotube（CNT） addition were fabricated from spherical Ti–22 Al–25 Nb powder by sintering in the B2 single-phase region. Phase identification and microstructural examination were performed to evaluate the effect of carbon addition on the hardness of the alloys. Carbon was either in a soluble state or in carbide form depending on its concentration. The acicular carbides formed around 1050℃ were identified as TiC and facilitated the transformation of α2 ＋ B2 → O. The TiC was located within the acicular O phase. The surrounding O phase was distributed in certain orientations with angles of 65° or 90° O phase particles. The obtained alloy was composed of acicular O, Widmanstatten B2 ＋O, and acicular TiC. As a result of the precipitation of carbides as well as the O phase, the hardness of the alloy with 2.0 wt% CNT addition increased to HV 429 ± 9.

关键词： Ti2AlNb alloy carbides microstructure precipitation hardening hardness

Hot Compression Behavior of As-Cast precipitation-hardening Stainless Steel

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Journal of Iron and Steel Research(International) 2007年第5期14卷 66-70页

作者： A Momeni S M Abbasi A Shokuhfar Advanced Materials Research Laboratory KNT University of Technology

High temperature deformation characteristics of a semiaustenitic grade of precipitation-hardening stain- less steels were investigated by conducting hot compression tests at temperatures of 900--1 100 ℃ and strain rates of 0. 001--1 s^-1. Flow behavior of this alloy was investigated and it was realized that dynamic recrystallization （DRX） was responsible for flow softening. The correlation between critical strain for initiation of DRX and de- formation parameters including temperature and strain rate, and therefore, Zener-Hollomon parameter （Z） was studied. Metallographic observation was performed to determine the as-deformed microstructure. Microstructural observation shows that recrystallized grain size increases with increasing the temperature and decreasing the strain rate. The activation energy required for DRX of the investigated steel was determined using correlations of flow stress versus temperature and strain rate. The calculated value of activation energy, 460 kJ/mol, is in accordance with other studies on stainless steels. The relationship between peak strain and Z parameter is proposed.

关键词： hot compression precipitation hardening stainless steel dynamic recrystallization

precipitation BEHAVIOUR AND hardening OFB2-ORDERED Ni(Al, Ta)

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Acta Metallurgica Sinica(English Letters) 1997年第2期10卷 99-104页

作者： W.H. Tian and M. Nemoto2(Department of Materials Physics, University of Science and Technology Beijing, Beijing 100083, China)(Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, 812,Fukuoka, Japan) Univ of Science and Technology Beijing Beijing China

precipitation of Ni2Al in supersaturated NiAl containing Ta and corresponding hardening have been investigated by hardness measurements and by transmission electron microscope observations. Selected area electron diffraction, high resolution electron microscopy and energy dispersive X-ray spectrometer analysis have shown that the Ni2Al with a hexagonal structure precipitates coherently in the B2-NiAl matrix. Ni2Al is an ordered phase with a. unit cell parameter, aNi2All=aNiAl and CNi2Al= aNiAl. The orientation relationship between the Ni2Al precipitate and the B2-NiAl matrix is (0001)Ni2Al (111)NiAl and [1120]Ni2Al[110]NiAl. NiAlhardens appreciably by the precipitation of Ni2Al phase.

关键词： intermetallic compound precipitation hardening TEM HREM,EDS

Investigation on precipitation hardening High Strength IF Steel Sheet for Automotive Application

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Journal of Iron and Steel Research(International) 2011年第S1期18卷 742-746页

作者： WANG Xu,LIU Ren-dong,WANG Ke-qiang,GUO Jin-yu,LIN Li,XU Rong-jie (Automobile and Home Appliance Steel Institute of Ansteel Company Limited Technology Centre,Anshan 114009,Liaoning,China) Ansteel Co Ltd Technol Ctr Automobile & Home Appliance Steel Inst Anshan 114009 Liaoning Peoples R China

High strength IF steel sheets with sufficient formability had been extensively used in automotive industry.In this paper,a new type of high strength cold-rolled IF steel with higher carbon and niobium contents was studied.Thermal plastic and continuous annealing were performed on thermo-mechanical simulator.The transformation points were tested by thermal expansion apparatus.Optical microscopy and transmission election microscope (TEM) were used to analyze the microstructure and the secondary precipitates of the steel.The results showed,the ductibility temperature range was from 950℃ to 1250℃ and the transformation points were 887℃ and 913℃ respectively.The grain size of this steel was smaller than that of conventional high strength IF steel.At the mean time,there were many fine Nb(C,N) precipitates distributed in the intra-granular regions and the PFZ (precipitate free zone) were formed in the neighborhood of grain boundaries.Due to the unique micro-structural feature,the yield strength and the yield ratio of the steel were decreased while the tensile strength was increased.With the increasing of the annealing temperature,the strength decreased,the total elongation A50,r-value at 15% strain and n-value were all increased.In order to obtain the favorable mechanical properties,the skin-pass rolling rate should be chosen at 0.6-0.8%.

关键词： high strength IF steel precipitation hardening grain refinement precipitate free zone (PFZ)

Cu precipitation and hardening Behaviour in Cu Added 0.19%C-1.5% Mn Martensitic Ultra-High Strength Steels

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Cu Precipitation and Hardening Behaviour in Cu Added 0.19%C-...

A strong and ductile NiCoCr-based medium-entropy alloy strengthened by coherent nanoparticles with superb thermal-stability

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作者： Yasunobu Nagataki Toru Hoshi Kaoru Sato Yoshihiro Hosoya The Ferrous Nano-Metal Consortium JRCM JFE Steel Corp Kokan-cho Fukuyama Hiroshima-prf 721-8510 Japan

Cu precipitation and hardening behaviour of Cu added 0.19%C-1.5%Mn steels were investigated to elucidate the effectiveness of nano size Cu particle dispersion in tempered martensite matrix as the alloy design of ultra-high strength steels with superior formability. In this work, hardness measurement, TEM observation, lattice parameter measurement and tensile testing were conducted for the 0.19%C-1.5%Mn steels with addition of up to 4%Cu those were water-quenched followed by aging at 250 through 550 for 20 seconds through 360 minutes.Cu added steels exhibited higher hardness than a Cu free steel in each aging condition and the hardenability was proportional to the Cu content. TEM observation revealed that the strengthening in Cu added steels was due to precipitation hardening by Cu particles. From the lattice parameter measurement, it is observed that Cu precipitation started at the aging time of 20 seconds and abruptly increased in the early stage of aging at 450℃. At the aging time of 60 minutes at maximum precipitation hardening, precipitated Cu content was estimated to be 2.5%. Smaller estimated activation energy for Cu precipitation than that of Cu diffusion in bcc-Fe matrix also suggested that high dislocation density introduced by martensitic transformation acted as the nucleation site or accelerated the diffusion of Cu.Regarding the tensile properties of the aged Cu free and 4%Cu steels, 4%Cu steel exhibited superior balance of tensile strength and elongation with tensile strength level of 1300MPa. This result indicates that dispersing nano Cu particles in tempered martensite matrix could give new design of ultra-high strength steels with superior formability.

关键词： Cu Addition Ultra-High Strength Steel precipitation hardening

来源： cnki会议评论

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Journal of Materials Science & Technology 2023年第1期132卷 201-212页

作者： D.D.Zhang J.Kuang H.Xue J.Y.Zhang G.Liu J.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China

In this work,we designed a novel NiCoCr-based medium-entropy alloy(MEA)strengthened by coher-ent L12-nanoparticles,i.e.,(NiCoCr)92 Al 6 Ta 2(at.%).The strengthening and deformation mechanisms of the material and the coarsening kinetics of the coherent precipitates were systematically investigated.The results indicated that giant precipitation hardening and its synergy with other strengthening contributors confer on the aged material a yield strength as high as 1.0 GPa.Moreover,a unique particle-features-dependent plasticity mechanism was revealed in this alloy.That is,the alloy with a lower volume frac-tion,denser distribution,and finer particles mainly deformed by dislocation planar slip,otherwise,stack-faults-mediated plasticity was favored,rationalized by the cooperative/competitive effect of stack-fault energy,spatial confinement,and applied stress.Furthermore,the coarsening behavior of precipitate fol-lowed a modified Lifshitz-Slyozov-Wagner(LSW)model,and the nanoparticles displayed remarkably su-perior thermal stability compared to most traditional superalloys and reported multicomponent alloys.The superb coarsening resistance of precipitate originated from the coupled effect of intrinsic sluggish diffusion in multi-principal alloys and the dual-roles of Ta species as a precipitate stabilizer.This work provides a new pathway to develop strong-yet-ductile multicomponent alloys as promising candidates for high-temperature applications.

关键词： Medium-entropy alloy Mechanical properties precipitation hardening Deformation mechanisms Coarsening kinetics