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Journal of Materials Science & Technology 2021年第31期90卷 85-94页

作者： Youfang Cao Longtao Jiang Deng Gong Guoqin Chen Ziyang Xiu Yangming Cheng Xiufang Wang Gaohui Wua School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China State Key Laboratory of Advanced Welding Production Technology Harbin Institute of TechnologyHarbin 150001China Shanghai Institute of Microsystem and Information Technology Chinese Academy of SciencesShanghai 200050China

In this paper,we were devoted to quantitatively analyzing the dimensional change of 2024 Al alloy during the aging process.Types of precipitates have been defined and the corresponding volume fraction has been measured with Transmission Electron Microscopy(TEM)and Three-Dimensional Atom Probe Tomography(3 D-APT).Guinier-Preston-Bagaryatsky(GPB)zone(0.86 vol.%)was found after aging for 8 h.GPB zone(0.17 vol.%)and S'phase(1.02 vol.%)was found after aging for 24 h.The reduced dimensional change was attributed to the reduction of matrix lattice parameter.Relative to the initial supersaturated solid solution state,the lattice strain of-2.79×10^(-5)and-5.16×10^(-5)was produced after 8 h and 24 h aging respectively.The difference of the lattice parameters between the precipitates and matrix was also considered.A model was established to quantitatively describe the relationship between the precipitation process and dimensional change of 2024 Al alloy.

关键词： Aluminum alloy Aging Atom probe tomography(APT) Dimensional stability precipitate

Effect of Aging on the Microstructure and Mechanical Properties of 1460 Alloy

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Acta Metallurgica Sinica(English Letters) 2015年第4期28卷 454-459页

作者： Juan Ma De-Sheng Yan Li-Jian Rong Yi-Yi Li Institute of Metal Research Chinese Academy of Sciences

Effects of the aging temperature on the hardening response, the tensile properties and the precipitate micro- structure evolution of 1460 alloy were studied in this work. It was found that Al3 （Sc, Zr） and δ′ （Al3Li） phases were precipitated from the matrix at the very early aging stage, while the precipitation of T1 （Al2CuLi） and θ′ （Al2Cu） was much slower than that of the δ′ phase. When aging at higher temperature （160 and 190 ℃）, the δ′, T1 and θ′ phases tended to form simultaneously and grow up very quickly. Conversely, the δ′ and θ″ （Al2Cu） phases were precipitated separately and more dispersive at lower aging temperature （130 ℃）. Taken together, the alloy aged at 160 ℃ exhibited improved mechanical properties owing to the uniform dispersion of the fine T1 precipitates.

关键词： Al-Li alloy precipitate Precipitation hardening process Mechanical property

Effects of B segregation on Mo-rich phase precipitation in S31254 super-austenitic stainless steels:Experimental and first-principles study

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Chinese Physics B 2022年第11期31卷 445-454页

作者：徐攀攀马晋遥姜周华张翊梁超雄董楠韩培德无 College of Materials Science and Engineering Taiyuan University of TechnologyTaiyuan 030024China Instrumental Analysis Center Taiyuan University of TechnologyTaiyuan 030024China Taiyuan Iron and Steel(Group)Company Ltd Taiyuan 030024China School of Metallurgy Northeastern UniversityShenyang 110167China

Precipitation in super-austenitic stainless steels will significantly affect their corrosion resistance and hot workability.The effects of Cr and Mo on precipitation behaviors were mainly achieved by affecting the driving force for precipitation,especially Mo has a more substantial promotion effect on the formation of theσphase than Cr.In the present study,B addition to the S31254 super-austenitic stainless steels shows an excellent ability to inhibit precipitation.The effect of B on the precipitation behaviors was investigated by microstructure characterization and theoretical calculations.The experimental observation shows that the small addition of B inhibits the formation of theσphase along grain boundaries and changes from continuous to intermittent distribution.Moreover,the inhibitory effect increased obviously with the increase of B content.The influence of B addition was theoretically analyzed from the atomic level,and the calculation results demonstrate that B can inhibit the formation ofσphase precipitates by suppressing Mo migration to grain boundaries.It is found that B and Mo are inclined to segregate atΣ5 andΣ9 grain boundaries,with B showing the most severe grain boundary segregation tendency.While B distribution at the grain boundary before precipitation begins,the segregation of Mo and Cr will be restrained.Additionally,B’s occupation will induce a high potential barrier,making it difficult for Mo to diffuse towards grain boundaries.

关键词： super-austenitic stainless steel precipitate segregation boron

Roles of titanium-rich precipitates as inoculants during solidification in low carbon steel

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International Journal of Minerals,Metallurgy and Materials 2010年第3期17卷 276-281页

作者： Ming-lin Wang Guo-guang Cheng Sheng-tao Qiu Pei Zhao Yong Gan The State Key Laboratory for Advanced Steel Process and Products Central Iron and Steel Research Institute Beijing 100081 China National Engineering and Research Center for Continuous Casting Technology Central Iron and Steel Research Institute Beijing 100081 China Metallurgical and Ecological Engineering School University of Science and Technology Beijing Beijing 100083 China

The effect of titanium on the as-cast structure and the growth form of titanium precipitates, and the effect of cooling rate on the size and distribution of titanium precipitates were studied. It is shown that Ti-rich precipitates acting as heterogeneous nucleation sites play an important role in refining the grain size and increasing the equiaxed grain ratio. Cooling rate has a great effect on the size and distribution of precipitates. The number of precipitates increases and the size decreases with the increase of cooling rate. Ti-rich particles acting as het- erogeneous nucleation sites at the onset of solidification are observed in the experiment. This result suggests that TiN nucleated on Ti2O3 is an effective inoculant for δ-ferrite during solidification in low carbon steel.

关键词： precipitate titanium oxide titanium nitride cooling rate solidification

Strengthening mechanisms of reduced activation ferritic/martensitic steels:A review

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International Journal of Minerals,Metallurgy and Materials 2021年第3期28卷 335-348页

作者： Jin-hua Zhou Yong-feng Shen Nan Jia Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education) School of Materials Science and EngineeringNortheastern UniversityShenyang 110819China The State Key Lab of Rolling&Automation Northeastern UniversityShenyang 110819China

This review summarizes the strengthening mechanisms of reduced activation ferritic/martensitic(RAFM)steels.High-angle grain boundaries,subgrain boundaries,nano-sized M_(23)C_(6),and MX carbide precipitates effectively hinder dislocation motion and increase high-temperature strength.M23C6 carbides are easily coarsened under high temperatures,thereby weakening their ability to block dislocations.Creep properties are improved through the reduction of M23C6 carbides.Thus,the loss of strength must be compensated by other strengthening mechanisms.This review also outlines the recent progress in the development of RAFM steels.Oxide dispersion-strengthened steels prevent M23C6 precipitation by reducing C content to increase creep life and introduce a high density of nano-sized oxide precipitates to offset the reduced strength.Severe plastic deformation methods can substantially refine subgrains and MX carbides in the steel.The thermal deformation strengthening of RAFM steels mainly relies on thermo-mechanical treatment to increase the MX carbide and subgrain boundaries.This procedure increases the creep life of TMT(thermo-mechanical treatment)9Cr-1W-0.06Ta steel by~20 times compared with those of F82H and Eurofer 97 steels under 550℃/260 MPa.

关键词： reduced activation ferritic/martensitic steel strengthening mechanism high-angle grain boundary subgrain boundary precipitate

Effect of Ti and rare earth on microsegregation and large-sized precipitates of H13 steel

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Journal of Iron and Steel Research(International) 2021年第12期28卷 1591-1604页

作者： Fa Ji Rui Xu Yu-long Gao Qing-chao Tian Lu Wang Zhi-xia Xiao Fu-xing Yin School of Materials Science and Engineering Hebei University of TechnologyTianjin300130China Research Institute for Energy Equipment Materials Hebei University of TechnologyTianjin300130China State Key Laboratory of Advanced Special Steel&Shanghai Key Laboratory of Advanced Ferrometallurgy&School of Materials Science and Engineering Shanghai UniversityShanghai200444China

Large-sized precipitates are fatal to the thermal fatigue of H13 hot work die steel.Different amounts of Ti and/or rare earth(RE)were added in H13 steel during electroslag remelting to improve the element segregation and refine the large-sized precipitates.The results show that as Ti content increases from 0.0032 to 0.057 wt.%,the segregation of Cr,Mo and V becomes more severe.V-rich M(C,N)carbides are shorter,and their branches are denser in 3D observation.Moreover,the number density of V-rich M(C,N)carbides with a size less than 2μm increases and that with other sizes decreases.In addition,Ti-rich MN nitrides with the size greater than 4μm increases significantly at high Ti content.When RE content increases from 0.0051 to 0.036 wt.%,the segregation of main alloying elements is first weakened and then aggravated.Compared with that in RE-free H13 steel,V-rich M(C,N)carbides are less developed in 3D observation,and the change in number density is similar to that of Ti-modified alloys.After composite modification of 0.024 wt.%Ti and 0.011 wt.%RE,the segregation of alloying element and V-rich M(C,N)carbides are not significantly improved.

关键词： H13 steel Segregation Primary carbide Ti Rare earth precipitate

Effect of nitrogen on microstructure and secondary hardening of H21 die steel

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Journal of Iron and Steel Research(International) 2019年第5期26卷 483-489页

作者： Jin-bo Gu Hua-qing Liu Jing-yuan Li Yan-bin Jiang Rui-jin Chang School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China Key Laboratory for Advanced Materials Processing of Ministry of Education University of Science and Technology Beijing Beijing 100083 China

The effect of nitrogen on the microstructure and secondary hardening of H21 die steel was studied by using scanning electron microscope, X-ray diffraction, transmission electron microscope and dilatometer. The results demonstrate that nitrogen can enhance the secondary hardening behavior of H21 hot-working die steel without toughness lose. Nitrogen addition increases the austenitic phase zone, decreasing austenite transformation temperature and martensite transformation temperature, thereby increasing the retained austenite stability. Retained austenite in quenched steel can dissolve a large quantity of alloy, thereby decreasing the coarsening rate of the precipitates. Trace nitrogen could intensify the refinement of pearlite by decreasing the diffusion rate of alloying element into carbides. Nitrogen increases the amounts and precipitation temperature of the undissolved V(C, N) and suppresses the growth of prior austenite before quenching. During tempering process, parts of nitrogen in V(C, N) dissolved back into the matrix, resulting in the distorting lattice of ferrite, thereby reinforcing the matrix. Meanwhile, the solid-dissolved nitrogen inhibits the growth of carbides by decreasing the diffusion rate of alloying elements.

关键词： Nitrogen Secondary hardening H21 die steel precipitate

Effect of Nd on microstructure and mechanical properties of as-extruded Mg-Y-Zr-Nd alloy

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Journal of Materials Science & Technology 2017年第9期33卷 926-934页

作者： Xiaoyang Xu Xianhua Chen Weiwei Du Yuxiao Geng Fusheng Pan The State Key Laboratory of Mechanical Transmissions College of Materials Science and EngineeringChongqing University National Engineering Research Center for Magnesium Alloys Chongqing University Chongqing Research Center for Advanced Materials Chongqing Academy of Science and Technology

The microstructure and mechanical properties of Mg-Y-Zr-x Nd alloys with 0–2.63 wt% Nd were investigated using optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and tensile testing test. Results indicated that more Mg;Y;particles and Mg;Nd;Y（β） phases were dispersed in the matrix when Nd content increased from 0 wt% to 2.63 wt% in the extruded alloys.Consequently, the nucleation of dynamic recrystallization and the volume fraction of recrystallized grains were promoted obviously. The average grain size can be refined in the range of 4.6–1.3 μm after the addition of 2.63 wt% Nd. The tensile strength of extruded alloys increased with increasing Nd content, and elongation exhibited an opposite change tendency. The extruded alloy sheet with 1.01 wt% Nd demonstrates optimal combination of strength and plasticity, i.e., the ultimate tensile strength, yield strength,and elongation were 273 MPa, 214 MPa, and 24.2%, respectively. Variations in mechanical properties are discussed on the basis of microstructure observations.

关键词： Mg-Y-Zr-Nd Extrusion Microstructure Tensile properties precipitate

DISLOCATION PINNING IN HIGH TEMPERATURE DEFORMED Ni_3(Al,Ti) SINGLE CRYSTALS CONTAINING DISORDERED γ precipitateS

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Acta Metallurgica Sinica(English Letters) 2006年第3期19卷 157-164页

作者： W.H. Tian M. Nemoto Department of Materials Physics and Ghemistry University of Science and Technology Beijing Beijing 100083 China Sasebo National Gollege of Technology Okishin 1-1 Sasebo 857-1193 Japan

A transmission electron microscopy （TEM） investigation has been performed on the dislocation pinning in Lie-ordered Ni3（Al, Ti） containing disordered γ precipitates.The morphology of deformation induced dislocations in the γ base alloys containing fine dispersion of disordered γ was investigated by means of weak-beam electron microscopy. The superdislocations are strongly attracted to the disordered particles and dissociate on the （111） plane in the γ particles, while they dissociate on the （010） plane in the γ＇ matrix. The disordered γ precipitates play an important role as a pinning point during the cross-slip of superdislocations from （111） to （010） planes in the γ matrix and restrain the cross-slip of superdislocations. The interaction of superdislocations with disordered particles causes the formation of superkinks, jogs and closed loops.

关键词： superdislocation precipitate attractive interaction cross slip Ll2-ordered Ni3Al

ELECTRON DIFFRACTION PATTERNS ANALYSIS OF precipitateS IN LD_(10) ALLOY

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中国有色金属学会会刊：英文版 1995年第3期5卷 119-123页

作者： Jin, Tounan Yin, Zhimin(Department of Materials Science and Engineering,Central South University of Technology, Changsha 410083) Central South Univ of Technology Changsha China

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关键词： precipitate simulated diffraction pattern transformation matrix