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预制体结构对SiC_(f)/SiC复合材料力学和热性能的影响

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Journal of Central South University 2024年第1期31卷 101-113页

作者：王徐辉吴宗绪陈招科伍艳熊翔 Science and Technology on High Strength Structural Materials Laboratory Central South UniversityChangsha 410083China State Key laboratory of Powder Metallurgy Central South UniversityChangsha 410083China

本文采用化学气相渗透法制备了具有二维多层、三维角联锁机织和多轴三维编织三种预制体结构的SiC_(f)/SiC复合材料。在综合分析纤维排列、SiC基体和孔隙分布的基础上,详细讨论了预制体结构对SiC_(f)/SiC复合材料力学性能和热性能的影响... 详细信息

本文采用化学气相渗透法制备了具有二维多层、三维角联锁机织和多轴三维编织三种预制体结构的SiC_(f)/SiC复合材料。在综合分析纤维排列、SiC基体和孔隙分布的基础上,详细讨论了预制体结构对SiC_(f)/SiC复合材料力学性能和热性能的影响。结果表明,复合材料的力学性能和热导率受纤维排列方式和复合材料密度的综合影响,而热膨胀系数主要受纤维排列方式的影响。此外,二维多层复合材料、三维角联锁机织复合材料和多轴三维编织复合材料的热导率可以分别用串联模型和平行模型来解释。多轴三维编织复合材料由于内部具有连续的可以作为热流快速通道的三维网状SiC基体层,因此具有较高的室温热导率。而随着温度的升高,SiC声子间的散射逐渐增强,SiC基体层在多轴三维编织复合材料中作为声子传播快速通道的作用逐渐减弱,热导率随温度降低的趋势更明显。

关键词：预制体结构抗弯强度热导率热膨胀系数 SiC_(f)/SiC复合材料

湿磨与SPS烧结制备Al添加ODS钢的显微组织结构与力学性能研究

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Journal of Central South University 2021年第4期28卷 1219-1232页

作者：孙煜舟吝楠章伍军张永森李忠涛韩现奇吴正刚王祖勇马超 College of materials science and Engineering Hunan UniversityChangsha 410082China National Key laboratory of science and technology on high-strength structural materials Central South UniversityChangsha 410083China

本文利用湿磨和放电等离子烧结技术制备了Al含量分别为0,1 wt%,2 wt%和3 wt%的15Cr-ODS钢。通过XRD、SEM、TEM、EBSD和拉伸测试等对ODS钢的显微组织结构与力学性能进行了研究。研究结果表明,Al元素的添加能够显著细化Fe-Cr相基体中的析... 详细信息

本文利用湿磨和放电等离子烧结技术制备了Al含量分别为0,1 wt%,2 wt%和3 wt%的15Cr-ODS钢。通过XRD、SEM、TEM、EBSD和拉伸测试等对ODS钢的显微组织结构与力学性能进行了研究。研究结果表明,Al元素的添加能够显著细化Fe-Cr相基体中的析出相颗粒,减小基体晶粒尺寸并改善材料的力学性能。Al添加ODS钢基体中尺寸为5~300 nm的弥散颗粒可以被标定为Al_(2)O_(3)与Y_(2)Ti_(2)O_(7)纳米粒子,这些弥散颗粒的尺寸分布较为不均匀。随着Al元素添加量的增加,材料的伸长率降低,但其抗拉强度显著的提升。当Al元素添加量为3 wt%时,15Cr3Al-ODS钢抗拉强度与伸长率分别为775.3 MPa和15.1%。Al元素的添加还可增强材料的耐腐蚀性能,Al含量为2 wt%ODS钢的腐蚀电位(Ecorr)与钝化电流密度(ipass)分别为0.39 V和2.61×10^(−3)A/cm^(2)(1.37 V)。因此,本文使用湿磨和放电等离子烧结方法制备的Al添加ODS钢在核能系统结构部件中能够具有良好的应用前景。

关键词： ODS钢氧化物纳米粒子微观结构拉伸强度弥散强化

Effect of Zr and Ti on isothermal oxidation behavior of Nb–Si based alloys

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Progress in Natural science:materials International 2022年第2期32卷 226-235页

作者： Ankang Sun Ziqiang Dong Shuang Yang Jintao Shu Yanjie Liu Yi Liu Yongwang Kang Dinggang Wang Jinxia Song materials Genome Institute Shanghai University science and technology on Advanced high Temperature structural materials laboratory Beijing Institute of Aeronautical Materials

The isothermal oxidation behavior of 56 Nb-16 Si-(20-x)Ti-3 Cr-3 Al-2 Hf-xZr(x=0,2,5,10 at.%) alloys was investigated at 800℃ and 1250℃,respectively.The results show that increasing the Zr content evidently increased the oxidation rates at 800℃,accompanied by the obvious occurrence of pesting oxidation.The alloys showed alike linear oxidation kinetics at 1250℃.With the increase of Zr content,the adherence and integrity of oxide scales were improved,but the overall oxidation resistance was slightly deteriorated.The observed oxidation behavior may be attributed to the composition variation of Zr and Ti in the alloys.The oxidation mechanism associated with the composition variation is discussed in this study.

关键词： Niobium Silicide Oxidation Zirconium Titanium

Controlling the Si/C ratio in SiC matrix based on the modified polymethysilane for C/C-SiC composites with enhanced mechanical properties

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Journal of Advanced Ceramics 2024年第2期13卷 220-236页

作者： Mingdong Liao Xiebo Hu Chenghao Zhong Ping Xu Xiaodong Wang Ze Zhang Peng Zhou Mingyu Zhang Zhean Su Qizhong Huang National Key laboratory of science and technology on high-strength structural materials Central South UniversityChangsha 410083China

Fabricating SiC matrix with controllable Si/C ratio for C/C-SiC composites via precursor infiltration and pyrolysis is difficult to realize due to the absence of suitable precursors.Here,SiC precursors with Si-rich(Si/C=1.23),nearstoichiometric(Si/C=1.01),and C-rich(Si/C=0.88)pyrolyzed ceramics at 1200℃ were successfully synthesized by the novel modification of polymethysilane.The structure and ceramization of synthesized SiC precursors were studied,and C/C-SiC composites with similar Si/C ratio in SiC matrix were also fabricated.The results revealed that the defects and Young’s modulus of SiC matrix and the thermal residual stress on pyrolytic carbon coated carbon fiber were determined by the Si/C ratio.As a result,the Si/C ratio exerted significant effects on the crack deflection behavior and the mechanical properties of the composites.The composites with near-stoichiometric SiC matrix showed excellent mechanical properties because of the effective crack deflection and the moderate Young’s modulus of their SiC matrix.The flexural strength,flexural modulus,and compressive strength were 423±27 MPa,33.41±4.52 GPa,and 393±8 MPa,respectively.Meanwhile,after a heat treatment at 1600℃,the role of carbon fiber toughening was improved and accompanied by a decrease in mechanical properties for all composites,which was attributed to the increased defects in SiC matrix and the damaged interfaces by the thermal residual stress.

关键词： SiC precursor Si/C ratio polymethysilane C/C–SiC composites mechanical properties

Interface Design Strategy for GNS/AZ91 Composites with Semi-Coherent Structure

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Acta Metallurgica Sinica(English Letters) 2024年第3期37卷 467-483页

作者： Jing-Peng Xiong Yi-Qi Zeng Jin-Long Liu Wei-Cheng Wang Lan Luo Yong Liu Key laboratory of Lightweight and high strength structural materials of Jiangxi Province School of Advanced ManufacturingNanchang UniversityNanchang 330031China School of Physics and materials science Nanchang UniversityNanchang 330031China

The interfacial structure plays an important role in the mechanical properties of magnesium matrix composite(MMCs)reinforced with graphene nanosheet(GNS)due to their poor wettability with the Mg matrix.An interface design strategy was proposed to form the semi-coherent interfacial structure with superior bonding strength.The lattice mismatch and interfacial bonding strength between Mg/rare earth oxide/carbon were utilized as key characteristics to evaluate the interfacial structure.Lanthanum oxide(La2O3)was selected as the intermediate candidate due to its low lattice mismatch and high interfacial bonding strength.To identify the interfacial structure of Mg/La2O3/graphene,first-principles calculations were conducted to calculate the ideal work of separation and electronic structure of the interfaces.Results demonstrated the presence of strong ionic and covalent interactions at the interface,which theoretically verified the strong interfacial bonding strength among Mg/La2O3/graphene interfaces.To experimentally validate the interface strength,MMCs with the interface structure of Mg/La2O3/GNS were developed.The formation of in-situ La2O3 led to the successful attainment of semi-coherent structures between Mg/La2O3 and La2O3/GNS,resulting in high strength and good ductility of the composite.Overall,this work proposes a new approach to interface design in MMCs with an enhancement of mechanical properties.

关键词： Interface design strategy Magnesium matrix composite Graphene nanosheets Semi-coherent interface Mechanical properties

Morphological Evolution of Fe-Rich Phases in the AlSi_9Cu_3Mg_(0.19)(Fe)Alloy with the Addition of Minor Mn and Cr

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Acta Metallurgica Sinica(English Letters) 2018年第6期31卷 629-640页

作者： Zhi-Qiang Qiu Xiang-Chen Meng Qiu-Hong Yuan Xiao-Shu Zeng Xi-Xin Rao Yan Ding Lan Luo Yong Liu Key laboratory of Lightweight and high strength structural materials of Jiangxi Province Nanchang University Physical science and technology College Yichun University School of materials science and Engineering Nanchang University

The morphological evolution of Fe-rich phases in the Alalloy has been investigated with various contents of Fe,Mn,and Cr.The results show that coarse Chinese script Fe-rich phases appear in the alloy with 0.6 wt%Fe combined with trace Mn,while the blocky Fe-rich phases appear combined with trace Cr.Under the coexistence of trace Mn and Cr,a large number of fine Chinese script Fe-rich phases could be visible in the low iron-bearing AlSi_9Cu_3-alloy（0.60 wt%）.At high Fe level（1.30 wt%）,numerous Fe-rich phases with hexagonal morphologies are observed with the trace Cr,while fish-bone and pentagonal morphologies of Fe-rich phases could be simultaneously observed with the addition of both Mn and Cr.The results reveal that the trace Mn and Cr promote the morphological evolution of Fe-rich phases.The morphology evolution mechanism of Fe-rich phases has been discussed by using the atom radius and electronegativity differences of Fe,Mn,and Cr.

关键词： AlSi_9Cu_3Mg_（0.19）（Fe） alloy Fe-rich phase Sludge factor Microalloying Electronegativity differences

The microstructure of a single crystal superalloy after different aging heat treatments

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Rare Metals 2018年第3期37卷 210-216页

作者： Xiao-Dai Yue Jia-Rong Li Xiao-Guang Wang science and technology on Advanced high Temperature structural materials laboratory Beijing Institute of Aeronautical Materials

To study the influence of aging heat treatments on the microstructure of single crystal superalloys with high content of refractory elements and optimal the aging heat treatment regimes, a single crystal superalloy containing 22 wt% refractory elements was investigated.Results show that for the experimental alloy, even the homogenization-solution heat treatment for 25 h cannot homogenize the alloying elements completely. During primary aging heat treatment, γ＇ phase grows larger and turns to regular cubes. higher aging temperature induces larger γ＇ cubes. For specimens with primary aging heat treated at 1120 ℃,γ＇ morphology does not change apparently during secondary aging heat treatment. For specimens with primary aging heat treatment at 1150 ℃,γ＇phase in interdendrite grows obviously comparing with that in dendrites. By analyzing the precipitating kinetics of γ＇phase, it is found that owning to the dendrite segregation and different aging heat treatment temperatures, γ＇ phase at different regions grows under the control of different factors at different aging heat treatment stages. The two controlling factors that are driving forces of phase transformation and element diffusion rate induce obviously different growth rates of γ＇ phase. As a result, the γ＇-precipitating behaviors are variable based on different solute concentrations and aging temperatures. For advanced single crystal superalloys that are supposed to be used at relatively high temperatures, the final γ＇ size after aging heat treatment is suggested to be close to the crossing point of diffusion controlling curve and driving force controlling curve corresponding to the serving temperature. And then,high-temperature properties can be improved.

关键词： Single crystal superalloy Aging heat treatment γ＇ precipitation Kinetics

Influence of γ' precipitate on deformation and fracture during creep in PM nickel-based superalloy

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Progress in Natural science:materials International 2021年第2期31卷 303-309页

作者： Zichao Peng Jinwen Zou Jie Yang Gaofeng Tian Xuqing Wang science and technology on Advanced high Temperature structural materials laboratory Beijing Institute of Aeronautical MaterialsAECC

FGH96 is a powder metallurgy nickel based superally used for turbine disk of aero-engines. In the present study FGH96 alloy with four different γ’ precipitate microstructures were produced via solution heat-treatment with different cooling rates, and the maximum cooling rate reached 400°C/min which was a super cooling rate for Nickel-based superalloy. The creep tests were conducted for PM FGH96 alloy under the testing condition of 704°C and 690 MPa. The relationship between the creep properties and the distribution of γ’ precipitate was established. The creep mechanism was analyzed by using TEM and ACTEM, and the dislocation movement was studied at the atomic scale. The creep strain rate was calculated through a physically based crystal slip model established based on crystal plasticity. The calculated results were consistent with the test ones, illustrating the validity of the model. The fracture mechanism was also investigated, and the results showed that the creep cracks generated on the surface due to the oxidation. It was observed that the cracks propagated in different ways depending on the different average diameters of γ’ precipitate. With the decrease of the average γ’ precipitate size,the critical shearing stress increased and the resistance of the dislocation slipping increased. The fracture mechanism for the primary stage transformed from intragranular to intergranular due to the change of dislocation slipping.

关键词： PM FGH96 superalloy Microtwinning γ′ precipitate Fracture mechanism Physically-based creep model

Dislocation ordering and texture strengthening of naturally aged Al-Cu-Mg alloy

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Journal of materials science & technology 2022年第23期118卷 1-14页

作者： F.Liu Z.Y.Liu G.Y.He L.N.Ou School of materials science and Engineering Central South UniversityChangsha 410083China Key laboratory of Nonferrous Metal materials science and Engineering Ministry of EducationCentral South UniversityChangsha 410083China National Key laboratory of science and technology on high-strength structural materials Central South UniversityChangsha 410083China

Stability of grain structure,dislocation ordering and strengthening mechanisms of the naturally aged AlCu-Mg alloy after solution treatment are investigated by using optical microscope(OM),scanning electron microscope(SEM),electron back-scattered diffraction(EBSD),X-ray diffraction(XRD) and transmission electron microscope(TEM).Results show that {100},{100},{110} and {110}slip systems can be activated after solution treatment,which can promote the formation of {110}Goss texture.The combination effect of T-Al_(20)Cu_(2) Mn_(3) phase and Goss-oriented grains with large Taylor factor makes the solution-treated alloys display excellent stability of grain structure.The enhanced yield strength of the alloy is ascribed to grain-refine strengthening,dispersed particles strengthening,dislocation strengthening and texture strengthening.The coarsening of the second phase is responsible for softening of the alloy after annealing at 400 ℃+solution treatment at 475 ℃.

关键词： Al-Cu-Mg alloy Dislocation ordering Goss texture Grain structure stability Texture strengthening