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Cu-assisted austenite reversion and enhanced TRIP effect in maraging stainless steels

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Journal of Materials Science & Technology 2022年第9期104卷 52-58页

作者： M.C.Niu K.Yang J.H.Luan W.Wang z.b.jiao School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China Shi-changxu Innovation Center for Advance Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Department of Mechanical Engineering The Hong Kong Polytechnic UniversityHong KongChina Department of Materials Science and Engineering City University of Hong KongHong KongChina The Hong Kong Polytechnic University Shenzhen Research Institute ShenzhenGuangdongChina

Control of the formation and stability of reverted austenite is critical in achieving a favorable combination of strength,ductility,and toughness in high-strength *** this work,the effects of Cu precipitation on the austenite reversion and mechanical properties of maraging stainless steels were investigated by atom probe tomography,transmission electron microscopy,and mechanical *** results indicate that Cu accelerates the austenite reversion kinetics in two manners:first,Cu,as an austenite stabilizer,increases the equilibrium austenite fraction and hence enhances the chemical driving force for the austenite formation,and second,Cu-rich nanoprecipitates promote the austenite reversion by serving as heterogeneous nucleation sites and providing Ni-enriched chemical conditions through interfacial *** addition,the Cu precipitation hardening compensates the strength drop induced by the formation of soft reverted *** tensile deformation,the metastable reverted austenite transforms to martensite,which substantially improves the ductility and toughness through a transformation-induced plasticity(TRIP)*** Cu-added maraging stainless steel exhibits a superior combination of a yield strength of~1.3 GPa,an elongation of~15%,and an impact toughness of~58 J.

关键词： Maraging stainless steel TRIP effect Austenite reversion Cu-rich nanoprecipitate

Achieving ultrahigh strength and ductility in high-entropy alloys via dual precipitation

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Journal of Materials Science & Technology 2023年第35期166卷 67-77页

作者： J.M.Guo b.C.zhou S.Qiu H.J.Kong M.C.Niu J.H.Luan T.L.zhang H.Wu z.b.jiao Department of Mechanical Engineering Research Institute for Advanced ManufacturingThe Hong Kong Polytechnic UniversityHong KongChina The Hong Kong Polytechnic University Shenzhen Research Institute Shenzhen 518057China Department of Materials Science and Engineering City University of Hong KongHong KongChina State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China

The strength-ductility trade-offhas been a longstanding dilemma in metallic *** we report an innovative approach to achieve a high strength-ductility synergy via dual precipitation of sheared and bypassed precipitates.(Ni_(2) Co_(2) FeCr)_(96-x) Al_(4) Nb_(x)(at.%)alloys strengthened by nanoscale L12 particles and Laves precipitates were selected as a model for this study,and their precipitate microstructures and mechanical properties were thoroughly *** dual-precipitation-strengthened alloys exhibit a yield strength of more than 1400 MPa,an ultimate tensile strength of over 1800 MPa,and a uniform elon-gation of 18%,thus achieving a high strength-ductility *** analysis reveals that the nanoscale L1_(2) precipitates contribute to the strength via the particle shearing mechanism,whereas the Laves phase provides the strengthening through the Orowan bypass *** study of deformation microstruc-tures shows that the L1_(2) precipitates are sheared by stacking faults,which facilitates long-range disloca-tion gliding through the *** a result,deformation induces the formation of hierarchical stacking fault networks and immobile Lomer-Cottrell locks,which effectively enhance the work hardening ca-pability and plastic stability,thereby resulting in a high ductility at high strength *** are piled-up against the interface between the Laves precipitates and matrix,which increases the work hardening capability at the early stages of plastic deformation but causes stress *** dual precipitation strategy may be useful for many other alloys for achieving superior mechanical properties for technological applications.

关键词： High-entropy alloy Dual precipitation Precipitation strengthening Deformation mechanism

In situ neutron diffraction unravels deformation mechanisms of a strong and ductile Fe Cr Ni medium entropy alloy

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Journal of Materials Science & Technology 2022年第21期116卷 103-120页

作者： L.Tang F.Q.Jiang J.S.Wróbel b.Liu S.Kabra R.X.Duan J.H.Luan z.b.jiao M.M.Attallah D.Nguyen-Manh b.Cai School of Metallurgy and Materials University of BirminghamB152TTUnited Kingdom Institute of Metal Research Chinese Academy of SciencesShenyang 110016China Faculty of Materials Science and Engineering Warsaw University of Technologyul.Wołoska 141Warsaw 02-507Poland State Key Laboratory for Powder Metallurgy Central South UniversityChangsha 410083China Rutherford Appleton Laboratory ISIS FacilityDidcot OX110QXUnited Kingdom Department of Materials Science and Engineering City University of Hong KongKowloonHong KongChina Department of Mechanical Engineering The Hong Kong Polytechnic UniversityHung HomHong KongChina CCFE United Kingdom Atomic Energy AuthorityAbingdonOxfordshire OX143DBUnited Kingdom

We investigated the mechanical and microstructural responses of a high-strength equal-molar medium entropy FeCrNi alloy at 293 and 15 K by in situ neutron diffraction *** 293 K,the alloy had a very high yield strength of 651±12 MPa,with a total elongation of 48%±5%.At 15 K,the yield strength increased to 1092±22 MPa,but the total elongation dropped to 18%±1%.Via analyzing the neutron diffraction data,we determined the lattice strain evolution,single-crystal elastic constants,stacking fault probability,and estimated stacking fault energy of the alloy at both temperatures,which are the critical parameters to feed into and compare against our first-principles calculations and dislocation-based slip system *** density functional theory calculations show that the alloy tends to form shortrange order at room ***,atom probe tomography and atomic-resolution transmission electron microscopy did not clearly identify the short-range ***,at 293 K,experimental measured single-crystal elastic constants did not agree with those determined by first-principles calculations with short-range order but agreed well with the values from the calculation with the disordered configuration at 2000 *** suggests that the alloy is at a metastable state resulted from the fabrication *** view of the high yield strength of the alloy,we calculated the strengthening contribution to the yield strength from grain boundaries,dislocations,and lattice *** lattice distortion contribution was based on the Varenne-Luque-Curtine strengthening theory for multi-component alloys,which was found to be 316 MPa at 293 K and increased to 629 MPa at 15 K,making a significant contribution to the high yield *** plastic deformation,dislocation movement and multiplication were found to be the dominant hardening mechanism at both temperatures,whereas twinning and phase transformation were not *** is mainly due to the high stack

关键词： Medium entropy alloy Multi-component alloy Cryogenic temperature Neutron diffraction

Thermal stability and deformation mechanisms in Ni-Co-Fe-Cr-Al-Ti-Nb-type nanoparticle-strengthened high-entropy alloys

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Journal of Materials Science & Technology 2023年第36期167卷 171-183页

作者： J.X.Hou J.Y.zhang J.X.zhang J.H.Luan Y.X.Wang b.X.Cao Y.L.zhao z.b.jiao X.J.Liu W.W.Song P.K.Liaw T.Yang Department of Materials Science and Engineering Hong Kong Institute for Advanced StudyCity University of Hong KongHong KongChina School of Materials Science and Engineering Harbin Institute of Technology(Shenzhen)Shenzhen 518055China Department of Mechanical Engineering The Hong Kong Polytechnic UniversityHong KongChina Steel Institute RWTH Aachen UniversityAachen 52072Germany Institute of Materials Engineering University of KasselKassel 334125Germany Department of Materials Science and Engineering The University of TennesseeKnoxvilleTN 37996-2200USA City University of Hong Kong China

The precipitate morphologies,coarsening kinetics,elemental partitioning behaviors,grain structures,and tensile properties were explored in detail for L1_(2)-strengthened Ni_(39.9)Co_(20)Fe_(15)Cr_(15)Al_(6)Ti_(4-x)Nb_(x)b_(0.1)(x=0 at.%,2 at.%,and 4 at.%)high-entropy alloys(HEAs).by substituting Ti with Nb,the spheroidal-to-cuboidal precipitate morphological transition,increase in the coarsening kinetics,and phase decomposition upon aging at 800°C *** excessive addition of Nb brings about the grain boundary precipitation of an Nb-rich phase along with the phase decomposition from the L1_(2)to lamellar-structured D019 phase upon the long-term aging *** partially substituting Ti with Nb,the chemically complex and thermally stable L12 phase with a composition of(Ni_(58.8)Co_(9.8)Fe_(2.7))(Al_(12.7)Ti_(5.8)Nb_(7.5)Cr_(2.3))ensures the stable phase structure and clean grain boundaries,which guarantees the superb high-temperature mechanical properties(791±7 MPa for yielding and 1013±11 MPa for failure)at 700℃.Stacking faults(SFs)were observed to prevail during the plastic deformation,offering a high work-hardening capability at 700°*** anomalous rise in the yield strength at 800℃was found,which could be ascribed to the multi-layered super-partial dislocations with a cross-slip configuration within the L1_(2)particles.

关键词： High-entropy alloys Coarsening kinetics Coherent precipitation strengthening Mechanical properties

A comparative study on microstructure,nanomechanical and corrosion behaviors of AlCoCuFeNi high entropy alloys fabricated by selective laser melting and laser metal deposition

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Journal of Materials Science & Technology 2022年第36期131卷 221-230页

作者： Yaojia Ren Hong Wu bin Liu Yong Liu Sheng Guo zbjiao Ian baker State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China Department of Industrial and Materials Science Chalmers University of TechnologyGothenburg SE-41296Sweden Department of Mechanical Engineering The Hong Kong Polytechnic UniversityHong Kong 999077China Thayer School of Engineering Dartmouth CollegeHanover NH 03755-8000United States

The present study investigated the microstructure,nanomechanics,and corrosion behavior of AlCoCuFeNi high entropy alloys fabricated by selective laser melting(SLM)and laser metal deposition(LMD).The microstructure of SLM-processed specimens was mainly composed of columnar-grained bCC matrix(^90μm in width)and Cu-rich twinned FCC *** columnar grains grew epitaxially along the building direction and exhibited a strong{001}*** comparison,a coarse columnar-grained bCC matrix(^150μm in width)with a strongertexture,rod-like b2 precipitates,and large core-shell structured FCC phases were formed in the LMD-processed specimens due to the higher heat accumulation ***,the LMD-processed specimens showed a lower hardness,wear resistance,and corrosion resistance,but higher creep resistance and reduced Young's modulus than the SLM-processed *** cracks occurred in both types of specimens,which could not be completely suppressed due to Cu segregation.

关键词： Selective laser melting Laser metal deposition High entropy alloys Nanomechanics Corrosion

Frequency-domain analysis of fluid-structure interaction in aircraft hydraulic pipeline systems: numerical and experimental studies

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Journal of zhejiang University-Science A(Applied Physics & Engineering) 2024年第8期25卷 605-617页

作者： Yang DENG zongxia jiao Yuanzhi XU School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100191China Research Institute for Frontier Science Beihang UniversityBeijing 100191China Key Laboratory of Advanced Airborne Systems Beihang UniversityBeijing 100191China Ningbo Institute of Technology Beihang UniversityNingbo 315800China Tianmushan Laboratory Hangzhou 310023China

The fluid-structure interaction(FSI)in aircraft hydraulic pipeline systems is of great concern because of the damage it *** accurately predict the vibration characteristic of long hydraulic pipelines with curved segments,we studied the frequency-domain modeling and solution method for FSI in these pipeline *** partial differential equations(PDEs)are utilized to model the pipeline FSI,considering both frequency-dependent friction and bending-flexibility *** address the numerical instability encountered by the traditional transfer matrix method(TMM)in solving relatively complex pipelines,an improved TMM is proposed for solving the PDEs in the frequency domain,based on the matrix-stacking strategy and matrix representation of boundary *** proposed FSI model and improved solution method are validated by numerical cases and *** experimental rig of a practical hydraulic system,consisting of an aircraft engine-driven pump,a z-shaped aero-hydraulic pipeline,and a throttle valve,was constructed for *** magnitude ratio of acceleration to pressure is introduced to evaluate the theoretical and experimental results,which indicate that the proposed model and solution method are effective in practical *** methodology presented in this paper can be used as an efficient approach for the vibrational design of aircraft hydraulic pipeline systems.

关键词： Fluid-structure interaction(FSI) Frequency-domain analysis Aircraft hydraulic pipeline Pipeline vibration Transfer matrix method(TMM)

Probing the bardeen-Kiselev black hole with the cosmological constant caused by Einstein equations coupled with nonlinear electrodynamics using quasinormal modes and greybody bounds

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Communications in Theoretical Physics 2024年第6期76卷 102-119页

作者： S R Wu b Q Wang z W Long College of Physics Guizhou UniversityGuiyang 550025China College Pharmacy Guizhou University of Traditional Chinese MedicineGuiyang 550025China

In this work,we investigate a static and spherically symmetric bardeen-Kiselev black hole(bH)with the cosmological constant,which is a solution of the Einstein-non-linear Maxwell field *** compute the quasinormal frequencies for the bardeen-Kiselev bH with the cosmological constant due to electromagnetic and gravitational *** varying the bH parameters,we discuss the behavior of both real and imaginary parts of the bH quasinormal frequencies and compare these frequencies with the Reissner-Nordström-de Sitter bH surrounded by quintessence(RN-dSQ).Interestingly,it is shown that the responses of the bardeen-Kiselev bH with the cosmological constant and the RN-dSQ under electromagnetic perturbations are different when the charge parameter q,the state parameter w and the normalization factor c are varied;however,for the gravitational perturbations,the responses of the bardeen-Kiselev bH with the cosmological constant and the RN-dSQ are different only when the charge parameter q is ***,compared with the gravitational perturbations,the electromagnetic perturbations can be used to understand nonlinear and linear electromagnetic fields in curved spacetime *** interesting observation is that,due to the presence of Kiselev quintessence,the electromagnetic perturbations around the bardeen-Kiselev bH with the cosmological constant damps faster and oscillates slowly;for the gravitational perturbations,the quasinormal mode decays slowly and oscillates *** also study the reflection and transmission coefficients along with the absorption cross section in the bardeen-Kiselev bH with the cosmological constant;it is shown that the transmission coefficients will increase due to the presence of Kiselev quintessence.

关键词： quasinormal modes greybody factors bardeen-Kiselev black hole with cosmological constant

A Possible γ-Ray Pulsation from PSR J1740-5340b in the Globular Cluster NGC 6397

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Research in Astronomy and Astrophysics 2024年第1期24卷 285-291页

作者： jiao zheng Pengfei zhang Li zhang Department of Astronomy School of Physics and AstronomyKey Laboratory of Astroparticle Physics of Yunnan ProvinceYunnan UniversityKunming 650091China

Recently, a new radio millisecond pulsar(MSP) J1740-5340b, hosted in the globular cluster(GC) NGC 6397,was reported with a 5.78 ms spin period in an eclipsing binary system with a 1.97 days orbital period. based on a modified radio ephemeris updated by tool tempo2, we analyze the ~15 yr γ-ray data obtained from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope and detect PSR J1740-5340b's γ-ray pulsation at a confidence level of ~4σ with a weighted H-test value of ~26. by performing a phase-resolved analysis, the γ-ray luminosity in on-pulse interval of PSR J1740-5340b is L_(γ)~ 3.8 × 10^(33) erg s^(-1) using NGC 6397's distance of 2.48 kpc. And γ-rays from the on-pulse part of PSR J1740-5340b contribute ~90% of the total observed γ-ray emissions from NGC 6397. No significant γ-ray pulsation of another MSP J1740-5340A in the GC is *** that the previous four cases of MSPs in GCs, more data in γ-ray, X-ray, and radio are encouraged to finally confirm the γ-ray emissions from MSP J1740-5340b, especially starving for a precise ephemeris.

关键词： gamma-rays:galaxies (stars:)pulsars:individual(PSR J1740-5340b) (Galaxy:)globular clusters:individual(NGC 6397)

Effect of Al_(2)O_(3)on the Mechanical Properties of(b_(4)C+Al_(2)O_(3))/Al Neutron Absorbing Materials

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Acta Metallurgica Sinica(English Letters) 2024年第8期37卷 1411-1420页

作者： J.X.Cai b.M.Shi N.Li Y.Liu z.G.zhang Y.N.zan Q.z.Wang b.L.Xiao z.Y.Ma Shi‑Changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Nuclear Equipment Division Beijing Institute of Nuclear EngineeringChina Nuclear Power Engineering Co.Ltd.Beijing 100840China Department of Materials Science School of Mechanical EngineeringShenyang UniversityShenyang 110044China

b_(4)C/Al composites are widely utilized as neutron absorbing materials for the storage and transportation of spent nuclear *** order to improve the high-temperature mechanical properties of b_(4)C/Al composites,in-situ nano-Al_(2)O_(3)was introduced utilizing oxide on Al powder *** this study,the Al_(2)O_(3)content was adjusted by utilizing spheroid Al powder with varying diameters,thereby investigating the impact of Al_(2)O_(3)content on the tensile properties of(b_(4)C+Al_(2)O_(3))/Al *** was found that the pinning effect of Al_(2)O_(3)on the grain boundaries could hinder the recovery of dislocations and lead to dislocation accumulation at high *** the result,with the increase in Al_(2)O_(3)content and the decrease in grain size,the high-temperature strength of the composites increased *** finest Al powder used in this investigation had a diameter of 1.4μm,whereas the resultant composite exhibited a maximum strength of 251 MPa at room temperature and 133 MPa at 350℃,surpassing that of traditional b_(4)C/Al composites.

关键词： Al matrix composites Neutron absorbing materials (b_(4)C+Al_(2)O_(3))/Al composites High-temperature strength