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| 1 | Effects of Heat Treatment and Nitrogen on Microstructure and Mechanical Properties of 1Cr12NiMo Martensitic Stainless Steel显示文摘A series of heat treatments using the orthogonal experiment method were performed to study the microstructure and mechanical properties of 1Cr12NiMo martensitic stainless steel containing various nitrogen content addition. The results indicate that the optimal heat treatment is annealing at 830℃ for 1 h, austenitizing at 985℃ for 1 h followed by oil quenching, and tempering at 630℃ for 4 h followed by air cooling. Nitrogen addition to 1Cr12NiMo steel can effectively hinder the austenite grain growth, refine the martensite lath, and increase the strength and hardness. The impact toughness of this steel only shows a minor decrease as the nitrogen content increases. | Ruicheng Fan Ming Gao Yingche Ma Xiangdong Zha Xianchao Hao Kui Liu | 2012 | Journal of Materials Science & Technology2012，28，11： | 10 |
| 2 | Effect of cooling rate on microstructure,microsegregation and mechanical properties of cast Ni-based superalloy K417G显示文摘The effects of different solidification rates after pouring on the microstructures,microsegregation and mechanical properties of cast superalloy K417 G were investigated.Scheil-model was applied to calculate the temperature range of solidification.The casting mould with different casting runners was designed to obtain three different cooling rates.The microstructures were observed and the microsegregation was investigated.Also,high temperature tensile test was performed at 900?C and stress rupture test was performed at 950?C with the stress of 235 MPa.The results showed that the secondary dendrite arm spacing,microsegregation,the size and volume fraction of γ'phase and the size of γ/γ'eutectic increased with decreasing cooling rate,but the volume fraction of γ/γ' eutectic decreased.In the cooling rate range of 1.42?C s^(-1)–0.84?C s^(-1),the cast micro-porosities and carbides varied little,while the volume fraction and size of phase and γ/γ' eutectic played a decisive role on mechanical properties.The specimen with the slowest cooling rate of 0.84?C s^(-1) showed the best comprehensive mechanical properties. | Li Gong Bo Chen Long Zhang Yingche Ma Kui Liu | 2018 | Journal of Materials Science & Technology2018，34，5： | 9 |
| 3 | Changes of Oxygen Content in Molten TiAl Alloys as a Function of Superheat during Vacuum Induction Melting显示文摘Experimental studies on the melting process of titanium aluminum alloy have been pursued from the viewpoint of contamination.TiAl alloys were prepared with vacuum induction melting (VIM) in calcia crucibles at 1873 K and 1923 K in order to determine the behavior of the oxygen content as a function of temperature,time and frequency of power.The experiment results showed that alloys were uncontaminated except for the increasing of oxygen content which was introduced from the reaction CaO(s)=Ca(in TiAl)+O(in TiAl),and the standard Gibbs energy of the reaction was determined to be △G0 =274000 102.8T(J/mol).Oxygen content increased slowly with the melting time by about 50×10-6 wt pct/min,and decreased with induction melting frequency.Lower superheat and higher melting frequency can be used to reduce oxygen content increasing rate. | Bo Chen,Yingche Ma,Ming Gao and Kui Liu Institute of Metal Research,Chinese Academy of sciences,Shenyang 110016,China | 2010 | Journal of Materials Science & Technology2010，26，10： | 8 |
| 4 | Modeling of Filling and Solidification Process for TiAl Exhaust Valves During Suction Casting显示文摘Investment and suction casting (ISC) represents an economic and promising process route to fabricate automotive exhaust valves of γ-TiAl based alloys, but information available on the metal flow and the temperature changes during mould filling and solidification process for the ISC process is meager. A sequentially coupled mathematical flow-thermal model, based on the commercial finite-volume/finite-difference code FLOW-3D and the finite-element code PROCAST, has been developed to investigate the ISC process. In term of calculating the flow and temperature fields during the filling and solidification stages, potential defects including the gas bubbles and the surface air entrainment occurred in the mould filling process and the shrinkage porosities formed in the solidification process are predicted and the reasons for the formation of these defects are also analyzed. The effects of filling pressure difference control methods and moulds on gas bubble and surface air entrainment behavior are presented. It is found that by changing the filling pressure difference control methods from general suction casting to 'air leakage' suction casting and reducing air leakage flow rates, the gas bubbles are eliminated effectively, and the surface air entrainment attenuate dramatically. With resort to a mould with a tetragonal runner, the surface air entrainment decrease to the lowest level. Finally, the water analogue and suction casting experiments of exhaust valves are implemented for further validation of the simulation results. | Chao XIONG Yingche MA Bo CHEN Kui LIU Yiyi LI | 2013 | Acta Metallurgica Sinica(English Letters)2013，26，1： | 7 |
| 5 | Micro-segregation and Precipitation of Alloy 690 during Isothermal Solidification:the Role of Nitrogen Content显示文摘The segregation and precipitation behavior of Alloy 690 containing 0.001-0.11 wt% nitrogen during isothermal solidification at 1370 and 1355 ℃ have been investigated using optical microscopy (OM),electron probe microanalysis (EPMA) and transmission electron microscopy (TEM).The results indicate that the volume fraction of TiN-type nitride formed during isothermal solidification increases with the nitrogen content of Alloy 690.Segregation of Ti and Cr exists in samples solidified at 1370 and 1355℃.The Ti content in the residual liquid markedly decreases and the concentration of Cr increases when the nitrogen content of Alloy 690 increases.Furthermore,N and S also show segregation to some extent in the residual liquids at 1355℃.Accompanying by the segregation of Cr,Ti,C,N and S,sulfides and chromium nitrides form.In a low nitrogen content Alloy 690,sulfur segregates and precipitates in the form of Ti 4 C 2 S 2 and (Cr,Ti)S,but in the form of (Cr,Ti)S or CrS in a high nitrogen content Alloy 690.(Cr,Ti)N-type nitrides with an fcc crystal structure have been identified in a sample with 0.11 wt% nitrogen. | Rong Jiang Bo Chen Xianchao Hao Yingche Ma Shuo Li Kui Liu | 2012 | Journal of Materials Science & Technology2012，28，5： | 3 |
| 6 | Effect of Solution Annealing on Microstructure and Mechanical Properties of a Ni-Cr-W-Fe Alloy显示文摘The effect of solution annealing on the microstructure and mechanical properties of a Ni-Cr-W-Fe alloy developed for advanced 700?C ultra-supercritical power plants was investigated. Test samples in this study were subjected to different solution treatments and the same aging treatment(at 760?C for 1 h).When solution annealing temperature was elevated from 1020?C to 1150?C, the stress-rupture life at750?C/320 MPa was increased from 60 h to 300 h, the stress-rupture elongation was enhanced from12% to 17%, and the elongation of the tensile at 750?C was improved from 11% to 24%. All tensile and stress-rupture samples displayed an intergranular dimple mixed fracture. Intergranular micro-cracks had a great relationship with the morphology of grain boundary carbides. Most carbides retained the morphology of globular shape and continuous thin plate. After tensile and stress-rupture tests, a few carbides were converted into lamellar. The results showed that intergranular micro-cracks were easier to form at continuous thin plate carbides than at globular shape carbides. Lamellar carbides hardly caused the nucleation of micro-cracks. Besides, grain boundaries sliding and elements diffusion during stressrupture tests led to the formation of precipitate free zones, which accelerated the extension of microcracks and influenced the stress-rupture life. | Meiqiong Ou Yingche Ma Xianchao Hao Baifang Wan Tian Liang Kui Liu | 2017 | Journal of Materials Science & Technology2017，33，11： | 2 |
| 7 | Stress rupture properties and deformation mechanisms of K4750 alloy at the range of 650℃ to 800℃显示文摘The stress rupture properties and deform ation mechanism s of K4750 alloy at 650 ℃, 700 ℃, 750 ℃ and 800 ℃ were investigated. As the decrease of tem perature and stress, the stress rupture life gradually increased. A Larson-Miller Parameter (LMP) method was used for analyzing the stress rupture life under different conditions. The linear fitting formula between stress (σ) and LMP was derived as σ= 3166.455-119.969 ×LMP and the fitting coefficient w as 0.98. After testing, the dislocation configurations of all stress rupture samples w ere investigated by transm ission electron microscopy (TEM). The tem perature and stress had a significant impact on the deform ation m echanism, thereby affected the stress rupture life of K4750 alloy. As the increasing stress at a given tem perature, the deform ation m echanism gradually transform ed from Orowan looping to stacking fault shearing. Based on experim ental results, the threshold stress at 650 ℃, 700 ℃, 750 ℃ and 800 ℃ for the transition of deformation mechanism was estimated to be about 650 MPa, 530 MPa, 430 MPa and 350 MPa, respectively. Below the threshold stress,γ phase effectively hindered dislocation motion by Orowan looping mechanism, K4750 alloy had along stress rupture life. Slightly above the threshold stress, Orowan looping combining stacking fault shearing was the dom inant mechanism ,the stress rupture life decreased. As the further increase of stress, stacking fault shearing acted as the dominant deformation mechanism , the resistance to dislocation motion decreased rapidly, so the stress rupture life reduced significantly. | Meiqiong Ou Yingche Ma Weiwei Xing Xianchao Hao Bo Chen Leilei Ding Kui Liu | 2019 | Journal of Materials Science & Technology2019，35，7： | 2 |
| 8 | Influence of yttrium on purification and carbide precipitation of superalloy K4169显示文摘The effect of reactive element yttrium on purification and carbide precipitation of superalloy K4169 has been studied through vacuum induction melting.The results show that yttrium has a strong deoxidizing and desulfurizing ability,and the impurity elements of sulfur and oxygen in melting K4169 are greatly reduced to 2-5 ppm and 4-5 ppm,respectively.The metallurgical reaction product is mainly Y_(2)O_(3)and yttrium containing sulfides have not been observed.With the increase of the content of yttrium from0.005 wt.%to 0.033 wt.%,the morphology and size of MC carbides in casting are significantly influenced due to that the yttrium changes the diffusion of the carbide forming elements and solid fraction during solidification.In the alloys without yttrium,only isolated blocky or strip carbides exist,while skeletonlike carbides are observed in the alloys with yttrium.Both the average size and the number density of skeleton carbides decrease monotonously with yttrium content increasing.After yttrium increasing to 0.033 wt.%,a phase of hexagonal Ni17 Y2 is observed to precipitate in the form of symbiosis with MC carbide and matrix.The addition of yttrium is not beneficial for the properties of K4169 alloys at the room temperature,which is quite related to the MC carbides with a large skeleton-like morphology through the analysis of tensile fracture. | Shuting Cao Yaqian Yang Bo Chen Kui Liu Yingche Ma Leilei Ding Junjie Shi | 2021 | Journal of Materials Science & Technology2021，，27： | 1 |
| 9 | Effects of microstructure evolution on the deformation mechanisms and tensile properties of a new Ni-base superalloy during aging at 800℃显示文摘Tensile properties at room temperature of a new casting Ni-base superalloy during aging at 800℃ for0-1000 h were investigated.During aging,granular M23C6 carbides presented at grain boundaries and kept growing from dispersed particles to continuous networks.The γ’ phase significantly coarsened,with the morphology of some γ’ phase changed from spherical to rounded cubic shape after 1000 h.Three deformation mechanisms in relation to the γ’ diameter(dγ’) were identified:(ⅰ) weakly coupled dislocations(WCD) connected by anti-phase boundary(APB) traveled in pair across the γ/γ’ structure when dγ’ was small in the under-aged alloys;(ⅱ) strongly coupled dislocations(SCD) with reduced spacing compared to(ⅰ) sheared γ’ phase when dγ’ increased in the over-aged alloys;(ⅲ) dislocations occasionally by-passed γ’ phase when dγ’ was larger than 97 nm after aging for more than 300 h.The alloy obtained the peak strength when 20 h-aged with dγ’=44 nm which was in the transition between(ⅰ) and(ⅱ).The aginginduced variation in yield strength was correlated to the coarsening of γ’ phase using a theoretical model of precipitation strengthening in terms of the formation of APB.The calculated results suggested that the γ’ phase with a volume fraction of 23% contributed more than 61% of the peak-aged yield strength.Observation after fracture revealed that the alloys usually fractured at grain boundaries.High stress concentration around carbides resulted in cracks by carbides self-cracking and the initiation of cavities.The undesirable agglomeration of M23C6 at grain boundaries was harmful to the properties of the overaged alloys. | Kunlei Hou Min Wang Meiqiong Ou Haoze Li Xianchao Hao Yingche Ma Kui Liu | 2021 | Journal of Materials Science & Technology2021，，9： | 1 |
| 10 | Effect of boron addition on the microstructure and mechanical properties of K4750 nickel-based superalloy显示文摘The effect of boron addition at 0,0.007 wt.% and 0.010 wt.% on the microstructure and mechanical properties of K4750 nickel-based superalloy was studied.The microstructure of the as-cast and heat-treated alloys was analyzed by SEM,EPMA,SIMS and TEM.Lamellar M_(5) B_(3)-type borides were observed in boroncontaining as-cast alloys.After the full heat treatment,boron atoms released from the decomposition of M_(5) B_(3) borides were segregated at grain boundaries,which inhibited the growth and agglomeration of M_(23)C_(6) carbides.Therefore,the M_(23)C_(6) carbides along grain boundaries were granular in boron-containing alloys,while those were continuous in boron-free alloys.The mechanical prope rty analysis indicated that the addition of bo ron significantly improved the tensile ductility at room tempe rature and stress rupture properties at 750℃/430 MPa of K4750 alloy.The low tensile ductility at room temperature of 0 B alloy was attributed to continuous M_(23)C_(6) carbides leaded to stress concentration,which provided a favorable location for crack nucleation and propagation.The improvement of the stress rupture properties of boron-containing alloys was the result of the combination of boron segregation increased the cohesion of grain boundaries and granular M_(23)C_(6) carbides suppressed the link-up and extension of micro-cracks. | Xiaoxiao Li Meiqiong Ou Min Wang Long Zhang Yingche Ma Kui Liu | 2021 | Journal of Materials Science & Technology2021，，1： | 1 |
| 11 | Germ cell transplantation in infertility mouse显示文摘This work investigated the spermatogenesis in an infertility BALB/c-nu mouse model by reinfusing germline stem cells into seminiferous tubules. Donor germ cells were isolated from male FVB/NJ-GFP transgenic mice. Seminiferous tubule microinjection was applied to achieve intratubular germ cell transfer. The germ cells were injected into exposed testes of the infertility mice. We used green fluo-rescence and DNA analysis of donor cells from GFP transgenic mice as genetic marker. The natural mating and Southern blot methods were applied to analyze the effect of sperm cell transplantation and the sperm function after seminiferous tubule microinjection. The spermatogenesis was morphologi-cally observed from the seminiferous tubules in 41/60 (68.33%) of the injected recipient mice using allogeneic donor cells. In the colonized testes, matured spermatozoa were seen in the lumen of the seminiferous tubules. In this research, BALB/c-nu infertility mouse model, the recipient animal, was used to avoid immunological rejection of donor cells, and germ cell transplantation was applied to overcome infertility caused by busulfan treatment. These results demonstrate that this technique of germ cell transplantation is of great use. Germ cell transplantation could be potentially valuable to oncological patients. | XIE XiaYang TENG Yong MA LiangHong LIU LiJun WANG Xiang SONG YingChing XU Ping | 2008 | Chinese Science Bulletin2008，53，1： | 1 |
| 12 | Solidification Features of Ti45Al Alloys with Different Boron Addition显示文摘The effects of boron on the solidification behaviors of Ti45AlxB alloys were studied by high temperature samples. These samples were melted at 1823 K, followed by cooling to the designated temperature, and then quickly water-quenched to preserve the solidification features. Optical microscopy and scanning electron microscopy analysis shows that the solidus temperature of Ti45Al was really reduced by 20 K when adding 0.8 at. pct B, and it was also observed that boride precipitated before the appearance of β phase. Besides, solidification structure confirmed that B addition does not obviously refine β phase. α grain refinement by certain amount of B in alloy probably clarifies the mechanism of B refining lamellar microstructure at room temperature. | Weidong Wang Yingche Ma Bo Chen Ming Gao Kui Liu Yiyi Li | 2009 | Journal of Materials Science & Technology2009，25，6： | 1 |
| 13 | Effect of grain boundary precipitates on the stress rupture properties of K4750 alloy after long-term aging at 750℃for 8000 h显示文摘In K4750 alloy,the evolution of grain boundary(GB)precipitates,including the degradation of blocky MC carbide particles and the precipitation of granular/needle-likeηphase particles,were observed after longterm aging(LA)at 750℃for 8000 h.During MC degradation,the Ti and C released from the MC carbide combined with Ni and Cr,respectively,in theγ’matrix to formη-Ni_(3)Ti phase and Cr-rich M_(23)C_(6)carbide.Large amounts of granularηphase precipitated at GBs and the needle-likeηphase grew gradually from GBs toward the grain interior.Because of the growth of theηphase through absorbingγ’phase,γ-depleted zones were formed around theηphase.The evolution of the MC carbide andηphase was primarily responsible for the decrease of the stress rupture life and the increase of elongation.After an LA sample was tested at 750℃and 360 MPa,the residual strain distribution was investigated by electron backscatter diffraction(EBSD).The results showed that the residual strain mainly distributed at GBs,especially in the region of MC degradation and at the edges ofηphases,which was closely related to the appearance of phase interfaces.Microvoids/cracks easily initiated at phase interfaces,then easily extended along theγ-depleted zones,thus the stress rupture life of LA samples was substantially shorter than that of samples subjected to the standard treatment.In particular,because of large amounts of fine degraded MC,granular M_(23)C_(6)and granularηphase particles distributed at GBs after 750℃/8000 h LA and microvoid/crack formation could be hindered by the formation of dimples,which led to an increase of elongation. | Meiqiong Ou Yingche Ma Kunlei Hou Min Wang Guangcai Ma Kui Liu | 2021 | Journal of Materials Science & Technology2021，，33： | 1 |
| 14 | Segregation of Re at theγ/γ'boundary of Ni-based single crystal superalloys revealed by first-principles calculations based Monte-Carlo simulations显示文摘Nickel-based single crystal superalloys have been widely used in aero-engines and gas turbine engines.To improve the creep resistance,rhenium is often added to the alloys.However,it is not yet fully under-stood how the added Re elements distribute in the alloys and how the microstructure evolves with the addition of Re.Here,we performed extensive first-principles calculations based Monte-Carlo simulated annealing of Ni-Al-Re ternary alloys with different Re concentrations ranging from 0.5 at.%to 6.0 at.%.The results demonstrate that with the decreasing temperature,most of Re atoms stay in theγphase,while a few of Re atoms stay in theγ'phase and tend to occupy the Al positions.At low temperatures,the Re atoms segregate at theγ/γ'boundary,in good agreement with experiment.We find that the disorder-order transition temperature of the Ni-Al-Re ternary alloys increases with the Re concentration due to the Re-enhanced Al-Al ordering tendency.In addition,we observe that at low temperatures the Re segregation at theγ/γ'boundary promotes the formation of Ni 4 Re-or Ni 8 Re-like local structures as the Re concentration is over 2 at.%.The formation of a large amount of these local structures consumes the Re atoms in solid solutions,and thus from the solid-solution strengthening point of view,this would have a negative influence on the creep resistance of the superalloys.This work provides important atomistic insights on the Re distribution and its effects on the stability of superalloys. | Heyu Zhu Jiantao Wang Lei Wang Yongpeng Shi Mingfeng Liu Jiangxu Li Yun Chen Yingche Ma Peitao Liu Xing-Qiu Chen | 2023 | Journal of Materials Science & Technology2023，，12： | 0 |
| 15 | Microstructure evolution and stress rupture properties of K4750 alloys with various B contents during long-term aging显示文摘The relationship among B content,microstructure evolution and stress rupture properties of K4750 alloy during long-term aging were investigated.After aging at 800℃for 1000 h,the decomposition degree of MC carbides of K4750 alloys with 0 B,0.007 wt.%B and 0.010 wt.%B were basically identical,which indicated that B has no inhibition on MC carbide decomposition during long-term aging.The MC carbide decomposition was accompanied by the formation of M_(23)C_(6) carbides and a small number ofηphases,which was controlled by the outward diffusion of C and Ti combined with the inward diffusion of Ni and Cr from theγmatrix.In addition,M_(23)C_(6) carbides in boron-free alloy were in continuous chain and needle-likeηphases were precipitated near them,while M_(23)C_(6) carbides in boron-containing alloys remained in granular distribution and noηphases precipitation around them.Adding B could delay the agglomeration and coarsening of M_(23)C_(6) carbides during long-term aging,which was because the segregation of B at grain boundary retarded the diffusion of alloy elements,thus weakened the local fluctuation of chemical composition near grain boundary.The stress rupture samples of K4750 alloys with various B contents after aging at 800℃for 1000 h were tested at 750℃/380 MPa.The results indicated that the stress rupture properties of bo ron-containing alloys were significantly better than that of boron-free alloy,which could be attributed to the increase of grain boundary cohesion strength and the optimization of M_(23)C_(6) carbide distribution due to the addition of B. | Xiaoxiao Li Meiqiong Ou Min Wang Xiang dong Zha Yingche Ma Kui Liu | 2021 | Journal of Materials Science & Technology2021，，14： | 0 |
| 16 | Microstructural evolution and tensile property of 1Cr15Ni36W3Ti superalloy during thermal exposure显示文摘1Cr15Ni36W3Ti was thermally exposed at 580℃and 680℃,respectively,up to 3000 h.Theγ’phase and intergranular TiC carbides continuously coarsened during exposure.None ofη,laves orσphase was discovered in the exposed samples,indicating good microstructure stability under the present exposure conditions.The ripening process of theγ’phase could be well modelled utilizing the LSW theory.The evolutions of the yield and tensile strengths were monotonous during exposure at 580℃.However,a transition point in strengths was detected in the tensile samples exposed at 680℃for 300 h.Accordingly,the criticalγ’diameter was measured to be 13-14 nm.Theγ’/dislocations interaction mechanism transformed from shearing to looping with theγ’diameter exceeding the critical point.The combination of the weakly coupled dislocations model and the Orowan looping model yielded a critical diameter of 13.1 nm which coincided well with the measured one,indicating the applicability of these two strengthening models for 1 Cr15Ni36W3Ti.The present exposure conditions did not exert a profound effect on the fracture mode.All the tensile samples underwent a typically ductile fracture with a dimple pattern dominating the fracture surface.The dispersed deformation induced by the prevalence of dislocation looping in the over-aged tensile samples retarded the propagation of intergranular cracks.The declined precipitation hardening increment and the enhanced deformation homogeneity partially recovered the tensile ductility in the over-aged samples exposed at 680℃. | Haoze Li Ming Gao Min Li Yingche Ma Kui Liu | 2021 | Journal of Materials Science & Technology2021，，14： | 0 |
| 17 | Phase Characterization and Formation Behavior in 6 wt%Si High-silicon Austenitic Stainless Steel during Isothermal Aging显示文摘The precipitation behavior of different phases in a high-silicon stainless steel(6 wt%Si)during aging at 600–1050℃for24 h was investigated.The morphology,crystal structure and composition of various precipitates were detailly characterized using optical microscopy,scanning electron microscopy and transmission electron microscopy.Four phases were mainly identified:χ-phase,M_6C carbides,σphase and a new type of fcc-phase.During aging at 600–900℃,the main precipitate was(Cr,Mo and Si)-richχ-phase which was directly precipitated fromγmatrix.Theχ-phase was calibrated as bcc structure with a lattice parameter of 8.90?.The peak temperature for the precipitation ofχ-phase was 800℃,and it was dissolved when aging at temperatures above 1000℃.Theσ-phase was observed only at 700℃and grew next toχ-phase.Above 700℃,a new fcc-phase was found to be precipitated along withχ-phase,with a space group of Fd3c and a lattice parameter of 12.56?.The M_6C carbides started to be precipitated at 700℃in the vicinity ofχ-phase.And its amount basically increased with the increasing of temperature.An orientation relationship between M_6C/γwas found:[100]c//[100]γ,(001)c//(001)γ,i.e.,the cube-on-cube relationship. | Sihan Chen Tian Liang Yangtao Zhou Weiwei Xing Chengwu Zheng Yingche Ma JinMing Wu Guobin Li Kui Liu | 2021 | Acta Metallurgica Sinica(English Letters)2021，34，5： | 0 |
| 18 | Effects of cerium addition on the microstructure and stress rupture properties of a new nickel-based cast superalloy显示文摘The microstructure and stress rupture properties of a new nickel-based cast superalloy were investigated with the cerium(Ce)additions of 0,19,50,96,150,and 300 ppm,respectively.The results indicated that Ce was mainly found in M C and M 23 C 6 carbides,and it was also found to exist in the form of cerium-rich phases or inclusions.According to the microstructure evidence,Ce promoted the formation of M C carbides and aggravated the inhomogeneity of M 23 C 6 carbides along grain boundaries.It was also identi-fied that the average sizes of primary and secondaryγ’phases all decreased with the rising Ce content.The acceleration of Ti,Nb,and C segregations during solidification was attributed to the influence of cerium on the variation of carbides along grain boundaries.The stress rupture life experienced a signifi-cant drop as the Ce content increased from 19 to 300 ppm.Explorations showed that the degradation was mainly attributed to the severe degradation of M C carbides and the easily forming micro-voids around them caused by the Ce addition.In addition to that,the increments in the inhomogeneous distribution of M 23 C 6 carbides at grain boundaries and the accelerated coarsening rate ofγ’phases both induced the fracture under complex stress conditions. | Lirong Rong Min Wang Weiwei Xing Xianchao Hao Yingche Ma | 2023 | Journal of Materials Science & Technology2023，，28： | 0 |
| 19 | Effects of Oxygen on the Microstructure of Ti_(47)Al_(0.7)B Alloys显示文摘The effects of oxygen on the microstructure of Ti-47Al-0.7B (at. pct) alloy for as-cast automotive valves were investigated. Six alloys with oxygen content from 0.4 to 1.4 at. pct were prepared by induction melting and centrifugal casting in CaO crucible under protective atmosphere. The microstructures were observed by optical microscopy (OM) and scanning electron microscope (SEM). The results show that the increase of oxygen content led to grain refinement and enhanced the microhardness as well as the α 2 volume fraction in the TiAl-based alloys. | Yingche Ma Zhiguo Jiang Bo Chen Xiujuan Zhao Ming Gao Kui Liu Yiyi Li | 2010 | Journal of Materials Science & Technology2010，26，2： | 0 |
| 20 | High-Temperature Plasticity Enhanced by Multiple Secondary Phases in a High-Si Austenitic Stainless Steel显示文摘An austenitic stainless steel with 6 wt% Si and multiple secondary phases was produced with the aim to achieve enhanced plasticity during hot deformation.The micro structure of the steel after fracture was characterized via electron back-scattered diffraction,transmission Kikuchi diffraction and scanning transmission electron microscopy.From the tail of the gage to the necking region,the microstructure of the material evolved from low-angle grain boundaries(LAGB s) to mixtures of LAGBs and high-angle grain boundaries(HAGBs),and fine equiaxed recrystallized grains.The elongation to failure in the tensile test exceeds 167%.During the hot deformation,continuous dynamic recrystallization of the austenitic matrix was promoted by the multiple secondary phases.The dislocations introduced by the secondary phases were rearranged and continuously transformed into HAGBs.The initially coarse grains(30.5 μm) were refined into ultra-fine equiaxed grains(1 μm),which contributed significantly the enhanced plasticity during hot deformation of the steel.In the necking area of the sample,twins were nucleated in the stress concentration regions and accommodated the local strain by discontinuous dynamic recrystallization,which was also beneficial to improving the plasticity. | Sihan Chen Tian Liang Guangcai Ma Chengwu Zheng Deli Chen Yingche Ma Kui Liu | 2022 | Acta Metallurgica Sinica(English Letters)2022，35，9： | 0 |
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