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Journal of Materials Science & Technology 2022年第1期96卷 248-261页

作者： Seyedmohammad Tabaie Farhad Rézaï-Aria Bertrand C.D.Flipo Mohammad Jahazi Department of Mechanical Engineering École de Technologie Supérieure(ÉTS)H3C 1K3 MontrealQCCanada Institut Clément Ader(ICA) Universitéde ToulouseCNRSIMT Mines AlbiINSAUPSISAECampus Jarlard81013 AlbiFrance TWI Ltd Granta ParkGreat AbingtonCambridge CB216ALUnited Kingdom

The continuous growth in the manufacture of aerospace components such as blisks has led to an increase in the application of different hybrid materials fabricating methods,and thus the requirements for joining and strengthening of dissimilar welds.According to this goal,selective laser melted(SLM)Inconel718 was joined with forged AD730^(TM)nickel-based superalloy through linear friction welding(LFW)in this study.Microstructure variation,specifically with respect to secondary phases precipitation was investigated.The microhardness and strengthening mechanisms of the weldment were also studied.The precipitation(volume fraction and size of particles)at different regions of both sides of the weld line was characterized.Close to the weld line,the dissolution ofγ’/γ"and Laves phases and grain refinement occurred which reveals the effects of both compression strain and high temperature on recrystallization and high degree of elemental diffusion in the weld zone(WZ).It is shown that the size,volume fraction,and shape of secondary phases increased and changed(from spherical to long-striped for Laves particles)as we went from the WZ toward the base metal.However,the measured microhardness indicated that the strength of AD730^(TM)alloy depends significantly on the grain size,while strength in SLM Inconel 718 was dominated by shape(or size)and the presence of secondary phases(γ’/γ"and Laves).

关键词： Additive manufacturing Linear friction welding ni-based superalloy Precipitation Microhardness Strengthening mechanisms

Influence of Selective Laser Melting Process Parameters on Microstructure and Properties of a Typical ni-based superalloy

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Acta Metallurgica Sinica(English Letters) 2022年第10期35卷 1673-1687页

作者： Zhen Lu Chengcai Zhang Nana Deng Haiping Zhou Ruirui Fang Kuidong Gao Yukuo Su Hongbin Zhang School of Materials Science and Engineering Harbin Institute of TechnologyHarbin150001China College of Mechanical and Electronic Engineering Shandong University of Science and TechnologyQingdao266590China Jier Machine-Tool Group Co.Ltd Jinan250022China

The influence of selective laser melting(SLM)process parameters on the microstructure and mechanical properties of a typical ni-based superalloy was researched.The optimum parameters of P=170 W,V=0.8 m/s were determined,under which the SLMed samples exhibited both the largest relative density of 99.57%and the best mechanical properties,including the microhardness(329.3±3.8 HV),yield strength(726±8.1 MPa),ultimate tensile strength(900±5.9 MPa)and elongation((31.9±0.24)%).The average grain size ranges of SLMed samples are from 15.2 to 17.4μm,with a typical mixed grain structure.Owing to the high cooling rate and remelting during SLM process,a large number of low-angle grain boundaries(LAGBs),dislocations and sub-grains were formed,and the fraction of LAGBs reached above 65%.At the same time,the content of low-Σcoincidence site lattice(CSL)boundaries was mostly less than 1%,while there was almost noγ′phase precipitated in the matrix.The texture of SLMed samples was weak,and there was no obvious preferred growth direction.Combining with the microstructure characterization,both grain refinement strengthening and dislocation strengthening were considered as the main strengthening mechanisms.Moreover,the fracture mechanism of the optimum sample belonged to ductile fracture.

关键词： Selective laser melting ni-based superalloy Relative density Microstructure Mechanical property

A physically-based representative stress methodology for predicting stress rupture life of ni-based DS superalloy

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Chinese Journal of Aeronautics 2023年第6期36卷 174-185页

作者： Jia HUANG Zhenzhuo HE Shuangqi LYU Xiaoguang YANG Duoqi SHI Yantao SUN Yongzhao LYU Zhizhong FU Guolei MIAO Jianan SONG School of Aeronautics and Astronautics Central South UniversityChangsha 410083China Aviation Engineering College Civil Aviation University of ChinaGuanghan 618307China School of Energy and Power Engineering Beihang UniversityBeijing 100083China Beijing Aeronautical Engineering Technical Research Center Beijing 100076China Chengdu Holy Industry&Commerce Corp.LTD Pengzhou 611936China School of Mechanical and Electrical Engineering Central South UniversityChangsha 410083China

Smooth and three types of U-shape single-edge notched plate specimens adopted to experimentally investigate stress rupture behavior of ni-based Directionally Solidified(DS)superalloy at 850℃ exhibit notch weakening effect and multi-source cracking initiation near the notch root.However,stress rupture behavior of smooth and V-shape notched round bars at 1040℃ revealed by Li et al indicates notch strengthening effect and creep micro-holes originating mostly from the central portion.A combined creep-viscoplastic constitutive model is employed to analyze the distribution of stress,strain and stress Triaxial Factor(TF)near the notch root.The different stress distribution and creep restraint between asymmetric notched plate specimens and symmetric notched round bars are the main reasons for the corresponding failure mechanism.Meanwhile,a good qualitative relationship exists between TF value and stress rupture life of notched specimen.Especially,the area with maximum TF value(TF_(max))is highly consistent with creep damage initiation region.Hence,based on the distribution characteristics of the initial tensile loading,a representative stress method independent of time-changing creep load at the location of TF_(max) is conducted for life prediction.The predicted results of both smooth and notched plate specimens and round bars agrees well with the experimental results.

关键词： Creep Life model ni-based superalloy Notched round bar Single edge notch

Effect of Zr on solidification and microstructure of a ni-based superalloy with high Al and Ti contents

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China Foundry 2022年第1期19卷 17-26页

作者： Guang-di Zhao Xi-min Zang Fang Liu Wei-wei Zhang Shuo Gao Xue Li Jing Guo School of Materials and Metallurgy University of Science and Technology LiaoningAnshan 114051LiaoningChina Institute of Metal Research Chinese Academy of SciencesShenyang 110016China

The total content of Al and Ti in advanced ni-based wrought superalloys is up to 7.5wt.%,which makes it easier to form harmful nonequilibrium eutectic(γ+γ′)andηphase.It has been reported that the addition of certain amount of Zr can modify precipitation of the nonequilibrium phases obviously,but the mechanism is still controversial.The effect of Zr ranging fromni-based superalloy with high Al and Ti contents was investigated,eliminating the interferences of C and B.Results show that increase in Zr content significantly promotes the formation of eutectic(γ+γ′),ηand Zr-rich phase in the interdendritic region.Besides the Zr-rich phase,Zr dissolves slightly in the eutecticγ′and obviously in theηphase.An interesting phenomenon is discovered that the Zr addition significantly increases the area fraction of liquid pools and enlarges the forming range ofγdendrites,which suggests that Zr markedly retards the solidification.Zr affects the eutectic(γ+γ′)andηformation mainly due to the retard of solidification and dissolution of Zr in them.The retard of solidification obviously increases the residual liquid fraction and undercooling.Zr can serve as a forming element for the eutectic(γ+γ′)andηphase,and the obvious dissolution of Zr inηphase significantly decreases the critical concentration of Ti for its precipitation.

关键词： zirconium ni-based superalloy solidification behavior segregation

Role of carbon in modifying solidification and microstructure of a ni?based superalloy with high Al and Ti contents

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Journal of Iron and Steel Research(International) 2021年第1期28卷 98-110页

作者： Guang‑di Zhao Xi‑min Zang Wen‑ru Sun School of Materials and Metallurgy University of Science and Technology LiaoningAnshan 114051LiaoningChina Institute of Metal Research Chinese Academy of SciencesShenyang 110016LiaoningChina

The effect of carbon ranging from 0.014 to 0.071 wt.%on the solidification and microstructure of a ni-based superalloy with high Al and Ti contents was studied.The results show that the increase in carbon addition significantly increases the size and volume fraction of MC carbides and promotes the change of their morphology from blocky to elongated shape.However,the carbon addition obviously decreases the size and volume fraction of eutectic(γ+γ′)and reducesηphase and borides formation.The change in carbide characteristics is mainly because of the increasing carbide-forming element and carbides precipitation temperature with the increase in carbon which favors the growth of them along the interdendritic liquid film.MC carbides are formed at an earlier solidification stage than the eutectic(γ+γ′).The increased carbide formation consumes more Ti,which delays and reduces the eutectic(γ+γ′)precipitation.The delay of eutectic(γ+γ′)precipitation leads to a deeper undercooling,which significantly decreases the critical Ti concentration for its precipitation.This,in turn,lowers Ti/Al ratio in residual liquids ahead of the eutectic(γ+γ′)and hence reducesηformation subsequently.B and Zr are slightly enriched in the carbides,which are considered during discussing how carbon influences the eutectic(γ+γ′)precipitation.

关键词： Carbon ni-based superalloy Solidification Segregation Eutectic(γ+γ′) MC carbide

Molecular Dynamics Study of Tension Process of ni-based superalloy

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Acta Metallurgica Sinica(English Letters) 2020年第5期33卷 741-750页

作者： Hui Li Wan Du Yi Liu Materials Genome Institute Shanghai UniversityShanghai 200444China

To understand the atomistic mechanisms of tension failure of ni-based superalloy,in this study,the classical molecular dynamics(MD)simulations were used to study the uniaxial tension processes of both the ni/ni3 Al interface systems and the pure ni and ni3 Al systems.To examine the effects of interatomic potentials,we adopted embedded atom method(EAM)and reactive force field(ReaxFF)in the MD simulations.The results of EAM simulations showed that the amorphous structures and voids formed near the interface,facilitating further crack propagation within ni matrix.The EAM potentials also predicted that dislocations were generated and annihilated alternatively,leading to the oscillation of yielding stress during the tension process.The ReaxFF simulations predicted more amorphous formation and larger tensile strength.The atomistic understanding of the defect initiation and propagation during tension process may help to develop the strengthening strategy for controlling the defect evolution under loading.

关键词： ni-based superalloy Molecular dynamics Embedded atom method(EAM) Reactive force field(ReaxFF) Uniaxial tension

Methods and mechanisms for uniformly refining deformed mixed and coarse grains inside a solution-treated ni-based superalloy by two-stage heat treatment

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Journal of Materials Science & Technology 2021年第18期77卷 47-57页

作者： Guan-Qiang Wang Ming-Song Chen Hong-Bin Li Y.C.Lin Wei-Dong Zeng Yan-Yong Ma School of Mechanical and Electrical Engineering Central South UniversityChangsha 410083China Light Alloy Research Institute Central South UniversityChangsha 410083China State Key Laboratory of High Performance Complex Manufacturing Changsha 410083China College of Metallurgies and Energy North China University Science and TechnologyTangshan 063009China

The uniform refinement mechanisms and methods of deformed mixed and coarse grains inside a solution-treatment ni-based superalloy during two-stage annealing treatment have been investigated.The two-stage heat treatment experiments include an aging annealing treatment(AT)and a subsequent recrystallization annealing treatment(RT).The object of AT is to precipitate someδphases and consume part of storage energy to inhibit the grain growth during RT,while the RT is to refine mixed and coarse grains by recrystallization.It can be found that the recrystallization grains will quickly grow up to a large size when the AT time is too low or the RT temperature is too high,while the deformed coarse grains cannot be eliminated when the AT time is too long or the RT temperature is too low.In addition,the mixed microstructure composed of some abnormal coarse recrystallization grains(ACRGs)and a large number of fine grains can be observed in the annealed specimen when the AT time is 3 h and RT temperature is 980℃.The phenomenon attributes to the uneven distribution ofδphase resulted from the heterogeneous deformation energy when the AT time is too short.In the regions with a large number ofδphases,the recrystallization nucleation rate is promoted and the growth of grains is limited,which results in fine grains.However,in the regions with fewδphases,the recrystallization grains around grain boundaries can easily grow up,and the new recrystallization nucleus is difficult to form inside grain,which leads to ACRGs.Thus,in order to obtain uniform and fine annealed microstructure,it is a prerequisite to precipitate even-distributedδphase by choosing a suitable AT time,such as 12 h.Moreover,a relative high RT temperature is also needed to promote the recrystallization nucleation aroundδphase.The optimal annealing parameters range for uniformly refining mixed crystal can be summarized as:900℃×12 h+990℃×(40-60 min)and 900℃×12 h+1000℃×(10-15 min).

关键词： ni-based superalloy Aging annealing Recrystallization annealing Grain refinement Microstructural evolution Mixed grain microstructure

A novel annealing method to uniformly refine deformed mixed grain microstructure of a solution-treated ni-based superalloy

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Science China(Technological Sciences) 2021年第8期64卷 1741-1751页

作者： WANG GuanQiang CHEN MingSong LIN YongCheng LI HongBin ZENG WeiDong MA YanYong CAI JinLiang PENG ChengXu ZOU FenYang Light Alloy Research Institute Central South UniversityChangsha410083China School of Mechanical and Electrical Engineering Central South UniversityChangsha410083China State Key Laboratory of High Performance Complex Manufacturing Changsha410083China College of metallurgies and energy North China University of Science and TechnologyTangshan063009China

Increasing static recrystallization(SRX)nucleation rate and decreasing grain growth rate are the main ways to obtain uniform and fine grain microstructure by annealing treatment.However,it is contradictory to raise the SRX nucleation rate and reduce grain growth rate during isothermal annealing treatment.This is because the increase of the SRX nucleation rate needs to raise annealing temperature,while the decline of grain growth rate needs to reduce the annealing temperature.To solve the contradiction,a novel method named cooling recrystallization annealing treatment(CRT)is designed and verified.For the CRT,the relatively high annealing temperature in the primary stage can promote SRX nucleation,and the gradually decreased annealing temperature can reduce the growth rate of SRX grains.Besides,an aged treatment is first carried out to precipitate high content of theδphase before the CRT.Enoughδphases not only provide large numbers of sites for SRX nucleation but also limit the grain growth due to the pinning effect,especially in the primary high-temperature stage.The results show that the novel method can refine deformed mixed grain microstructure well when the suitable cooling rate,start and final recrystallization annealing temperatures are employed.The deformed mixed grain can be uniformly refined to an average size of 8.26μm with the route of 900℃×12 h+1020℃→970℃×20 min.

关键词： ni-based superalloy annealing method refinement mechanism grain uniformity microstructure evolution

Microstructure and mechanical properties of TiAl/ni-based superalloy joints vacuum brazed with Ti-Zr-Fe-Cu-ni-Co-Mo filler metal

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Rare Metals 2021年第8期40卷 2134-2142页

作者： Bao Wan Xiao-Qiang Li Cun-Liang Pan Dong-Yu Li Sheng-Guan Qu Chao Yang National Engineering Research Center of Near-Net-Shape Forming for Metallic Materials South China University of TechnologyGuangzhou510640China

For the purpose of elevated temperature service and weight reduction in aerospace vehicle applications,a novel Ti-Zr-Fe-Cu-ni-Co-Mo filler metal was employed to join TiAl to ni-based superalloy(GH536).The effects of brazing temperature on interfacial microstructure and chemical composition of the joints were analyzed.The representative joint microstructure from TiAl substrate to GH536 substrate was primarily composed of four characteristic layers in order:B_(2);Al_(3)niTi_(2);Alni_(2)Ti containing Cr-rich(Cr,ni,Fe)_(ss)(subscript ss represents solid solution),ni-rich(ni,Cr,Fe)_(ss) and Tini3;Cr-rich(Cr,ni,Fe)_(ss)containing Alni_(2)Ti,ni-rich(ni,Cr,Fe)_(ss) and Tini3.Layer IV has the majority of the brazing seam,while LayerⅡwas the thinnest.And the thickness of LayerⅡwas not affected by brazing temperature.With the increase in brazing temperature in the range of 1110-1170℃,both the shear strength and the thickness of brazing seam firstly increased and then decreased.The joint performance was jointly controlled by the thickness of brazing seam,the amounts of microcracks and intermetallic compounds formed in brazing seam.The maximum shear strength of 183 MPa at room temperature was obtained together with a peak thickness when the joint was brazed at 1150℃for 10 min and the shear fracture mainly occurred in the thinnest LayerⅡAl_(3)niTi_(2).

关键词： TiAl alloy ni-based superalloy Brazing Microstructure Shear strength