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Improvement on the Oxidation Resistance of a Ti_3Al Based Alloy by Cr1-xAl_xN (0≤x≤0.47) Coatings

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Journal of Materials Science & Technology 2007年第3期23卷 373-378页

作者： Ming ZHU Meishuan LI Shuwang DUO yanchun zhou Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Jiangxi Key Laboratory of Surface Engineering Jiangxi Science ＆ Technology Normal University Nanchang 330013 China

Cr1-xAlxN coatings have been deposited on a Ti3Al based alloy by reactive sputtering method. The results of the isothermal oxidation test at 800-900℃ showed that Cr1-xAlxN coatings could remarkably reduce the oxidation rate of the alloy owing to the formation of Al2O3＋Cr2O3 mixture oxide scale on the surface of the coatings. No spallation of the coatings or oxide scales took place during the cyclic oxidation at 800℃. Ti was observed to diffuse into the coatings, the diffusion distance of which was very short, and the diffusion ability of it was proportional to the AI content in the coatings. Compared to Ti, Nb can diffuse much more easily through the whole coatings and oxide scales.

关键词： Cr1-xAlxN coatings Oxidation Interdiffusion Ti3Al based alloy

Theoretical investigation on the stability, mechanical and thermal properties of the newly discovered MAB phase Cr4AlB4

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Journal of Materials Science & Technology 2020年第4期39卷 161-166页

作者： Fu-Zhi Dai Haiming Zhang Huimin Xiang yanchun zhou Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing100076China School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing100044China

The nanolaminated MAB phases have attracted great research interests in recent years due to their similarities to MAX phases,which display both metallic and ceramic-like *** the present work,a newly discovered MAB phase Cr4AlB4 was investigated by first principles *** evaluations indicate that Cr4AlB4 can be synthetized in Al lean condition,which can further transform to Cr2AlB2 in Al rich *** full set of elastic properties and their dependences on temperature,ideal strengths under different tensile and shear deformations,and thermal expansions of Cr4AlB4 were *** results reveal that the properties of Cr4AlB4 are dominated by the layered crystal structure and weak bonding nature between Al and Cr2B2 layers,including low elastic stiffness and large thermal expansion along[010]direction(the stacking direction of Al and Cr2B2 layers),low shear resistances in(010)plane,and preferentially cleavage along and/or shear in(010)***,it suggests that Cr4AlB4 displays similar mechanical properties to MAX phases,including readily machinable,thermal shock resistant,and damage *** combination with the fact that Cr,Al and B all can form dense oxides to protect the material from further oxidation,Cr4AlB4 is regarded as a promising high temperature ceramic.

关键词： MAB phase Cr4AlB4 First-principles Mechanical properties Thermal properties

Theoretical prediction on the stability, electronic structure, room and elevated temperature properties of a new MAB phase Mo2AlB2

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Journal of Materials Science & Technology 2019年第12期35卷 2926-2934页

作者： yanchun zhou Huimin Xiang Haiming Zhang Fu-Zhi Dai Science and Technofogy on Advanced Functional Composite Laboratory Aerospace Research institute of Maferids Processing Technofogy.No.1 South Dahongmen RoadBeijing 100076China School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China

Mo2AlB2 is a new MAB phase that has been observed in thin foils of Mo Al B during TEM observation and in Na OH etched Mo Al B samples. However, the structural characteristics, chemical bonding and properties of this new compound have not been investigated. In this work, geometry optimized crystal structure of Mo2AlB2 is obtained and its stability, elastic and thermal dynamic properties are investigated. Mo2AlB2 is stable in Al lean conditions, which is consistent with the exiting experimental results. It is also gauged as a damage tolerant or quasi-ductile ceramic based on the low Pugh’s shear to bulk modulus ratio(G/B = 0.544) and positive Cauchy pressure in all three crystallographic directions, which is underpinned by the metallic bonding. Mo2AlB2 also exhibits high stiffness which is attributed to the strong B–B covalent bond chains within its crystal structure. Due to the anisotropic chemical bonding, Mo2AlB2 has anisotropic thermal expansion coefficients αa= 6.19 × 10^–6 K1, αb= 12.13 × 10^-6 K^–1, αc= 6.66 × 10^-6 K^–1,respectively, along a, b and c directions in the temperature range between 300 and 1500 K. The heat capacity from 300 to 1500 K can be described as Cp= 120.32 + 0.01648 T-2.597 × 10^6 T^-2(J·mol^–1·K^–1).The elastic constants decrease almost linearly with temperature. The elastic constants representing the resistance to principle deformation(c11, c22 and c33) decrease in faster rates than those representing shear deformation resistance(c44, c55 and c66). Correspondingly, bulk and Young’s modulus decrease in faster rates than shear modulus. In light of the structure-property relations of Mo2AlB2, it is suggested that future damage tolerant ceramics can be designed by putting stiff covalent bonding units into soft metallic bonding box to obtain both high stiffness and quasi-ductility.

关键词： MAB phases Mo2AlB2 Damage tolerant ceramics Phase Stability Elastic properties Thermodynamic properties

M2M’AlB4（M = Mn, Fe, Co, M’ = Cr, Mo, W）: Theoretical predicted ordered MAB phases with Cr3AlB4 crystal structure

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Journal of Materials Science & Technology 2019年第7期35卷 1432-1438页

作者： Fu-Zhi Dai Huimin Xiang Yinjie Sun yanchun zhou Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials & Processing Technology

The nanolaminated MAB phases have attracted great research interests due to their unusual combination of metal-like and ceramic-like properties, which is similar to MAX phases. Recently, ordered quaternary MAX phases have been discovered, which enriches the family of MAX phases, and opens a new window to tailor the properties of MAX phases and to develop new MXenes. In the present work, we explored possible ordered quaternary MAB phases with Cr3AlB4 structure(space group: Pmmm) by first-principles calculations. The predictions show that M2M’AlB4 phases with M = Mn, Fe, Co and M’ = Cr, Mo, W exhibit strong tendency of ordering, where M locates at 2t site(0.5, 0.5, z2t) and M’ locates at 1 g site(0, 0.5,0.5). The main driving force of ordering may be the differences in bonding strengths between Al and M elements. Analyses on chemical bonds reveal that bonding strengths increase following the order:Al-Mn < Al-Fe < Al-Co, which is consistent with the prediction that ordering tendency increases when M changes from Mn to Co, as derived from enthalpy differences. The ordered M2M’AlB4 phases with M =Mn or Fe are predicted ferromagnetic and ordered M2M’AlB4 phases display lower shear resistance and possibly better ductility in comparison to Cr3AlB4.

关键词： MAB phase Ordered structure First-principle calculations Cr3AlB4 Chemical bonds Ultrahigh temperature ceramics

Cr5Si3B and Hf5Si3B:New MAB phases with anisotropic electrical,mechanical properties and damage tolerance

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Journal of Materials Science & Technology 2018年第8期34卷 1441-1448页

作者： yanchun zhou Huimin Xiang Fu-Zhi Dai Zhihai Feng Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyNo.1 South Dahongmen RoadBeijing 100076China

Through a combination of electronic structure, chemical bonding and mechanical property investigations, anisotropic electrical and mechanical properties, and damage tolerant ability of MAB phases CrsSi3 B and HfsSi3B are predicted. The anisotropic electrical conductivity is due to the anisotropic distribution of Cr in CrsSiaB and Hf in HfsSi3B, which mainly contribute to the electrical conductivity. The anisotropic mechanical properties are underpinned by the anisotropic chemical bonding within the crystal structures of CrsSi3B and HfsSi3B. The high stiffness is determined by the strong covalent-ionic Crl--B--Crl and Crl--Si bonds in CrsSi3B and the ionic-covalent Hfl--B--Hfl and Si--B bonds in HfsSi3B; while the low shear deformation resistance is attributed to the presence of metallic Cr--Cr, Hf--Hf and Si--Si bond. Based on the low Pugh＇s ratio, CrsSi3B and Hfs Si3B are predicted tolerant to damage. The possible cleavage plane is （0001） and the possible slip systems are 〈1 100〉1{11 20} and 〈11 20〉1{0001} for both CrsSi3B and HfsSi3B.

关键词： MAB phases CrsSi3B and HfsSi3 BFirst-principles calculations Mechanical properties Chemical bonding

Electrodeposition and Characterization of Ni/Ti_3Si(Al)C_2 Composite Coatings

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Journal of Materials Science & Technology 2011年第11期27卷 1016-1024页

作者： Ying Liang Mingyue Liu Jixin Chen Xiaoxia Liu yanchun zhou Department of Chemistry Northeastern University Shenyang 110819 China Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

Pure nickel and Ni/Ti3Si（AI）C2 composite coatings were prepared by electrodeposition method from an additive-free nickel Watt＇s bath and were characterized by X-ray diffraction, laser confocal microscopy and scanning electron microscopy. The effect of current and Ti3Si（AI）C2 concentration in the solution on the composition, grain size, preferred orientation and surface morphology of the electrodeposited coatings were investigated. （200）-oriented Ni coatings could be deposited at high current （62.5 mA）, while （220）-oriented Ni coatings could be obtained at low current （25 mA）. However, the presence of Ti3Si（Al）C2 particles disturbed the surface texture of Ni crystallites in the composite coatings. Based on the simulated morphology and the observed microstructure, the mechanisms for the change of preferred orientation and crystallite shapes in the presence of Ti3Si（Al）C2 particles were discussed. Moreover, microhardness and friction properties of pure nickel and Ni/Ti3Si（Al）C2 composite coatings were also compared.

关键词： Ni/TiaSi(Al)C2 composite coatings Electrodeposition Preferred orientation Microstructure Mechanical properties

Shear anisotropy： Tuning high temperature metal hexaborides from soft to extremely hard

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Journal of Materials Science & Technology 2017年第11期33卷 1371-1377页

作者： yanchun zhou Fuzhi Dai Huimin Xiang Bin Liu Zhihai Feng Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Material & Processing Technology Beijing 100076China School of Materials Science and Engineering Shanghai University Shanghai 200444 China

Easy machining into sharp lending edge, nose tip and complex shape components plays a pivotal role in the application of ultrahigh temperature ceramics in hypersonic vehicles, wherein low and controllable hardness is a necessary parameter to ensure the easy machinability. However, the mechanism that driving the hardness of metal hexaborides is not clear. Here, using a combination of the empirical hardness model for polycrystalline materials and density functional theory investigation, the hardness dependence on shear anisotropic factors of high temperature metal hexaborides has been established. It has come to light that through controlling the shear anisotropic factors the hardness of polycrystalline metal hexaborides can be tailored from soft and ductile to extremely hard and brittle, which is underpinned by the degree of chemical bonding anisotropy, i.e., the difference of B-B bond within the B;octahedron and that connecting the B;octahedra.

关键词： Microhardness Electronic structure Elastic constant Borides Structural ceramics

Preparation,mechanical,and thermal properties of a promising thermal barrier material:Y_(4)Al_(2)O_(9)

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Journal of Advanced Ceramics 2015年第2期4卷 94-102页

作者： yanchun zhou Xinpo LU Huimin XIANG Zhihai FENG Science and Technology of Advanced Functional Composite Laboratory Aerospace Research Institute of Materials and Processing TechnologyNo.1 South Dahongmen RoadBeijing 100076China

In our previous work,anisotropic chemical bonding,low shear deformation resistance,damage tolerance ability,low thermal conductivity,and moderate thermal expansion coefficient of Y_(4)Al_(2)O_(9)(YAM)were *** this work,phase-pure YAM powders were synthesized by solid-state reaction between Y2O3 and Al_(2)O_(3)and bulk YAM ceramics were prepared by hot-pressing *** parameters and a new set of X-ray powder diffraction data were obtained by Rietveld *** mechanical and thermal properties of dense YAM ceramics were *** measured elastic moduli are close to the theoretical predicted values and the stiffness can be maintained up to 1400℃.The flexural strength and fracture toughness are 252.1±7.3 MPa and 3.36±0.20 MPa·m^(1/2),*** tolerance of YAM was also experimentally *** measured average linear thermal expansion coefficient(TEC)of YAM is 7.37×10^(-6)K^(-1),which is very close to the theoretical predicted *** high-temperature X-ray diffraction(XRD)analysis,volumetric TEC is determined(23.37±1.61)×10^(-6)K^(-1)and the anisotropic TEC areaa=7.34×10^(-6)K^(-1),ab=7.54×10^(-6)K^(-1),andac=7.61×10^(-6)K^(-1).

关键词： Y4Al2O9 X-ray diffraction(XRD)pattern mechanical properties thermal expansion damage tolerance

High strength and high porosity YB2C2 ceramics prepared by a new high temperature reaction/partial sintering process

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Journal of Materials Science & Technology 2019年第12期35卷 2883-2891页

作者： Heng Chen Huimin Xiang Fuzhi Dai Jiachen Liu yanchun zhou Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education School of Materials Science and EngineeringTianjin UniversityTianjin300072China Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing100076China

Porous ultrahigh temperature ceramics(UHTCs) are potential candidates as reusable thermal protection materials of transpiration cooling system in scramjet engine. However, low strength and low porosity are the main limitations of porous UHTCs. To overcome these problems, herein, a new and simple in-situ reaction/partial sintering process has been developed for preparing high strength and high porosity porous YB2C2. In this process, a simple gas-releasing in-situ reaction has been designed, and the formation and escape of gases can block the shrinkage during sintering process, which is favorable to increase the porosity of porous YB2C2. In order to demonstrate the advantages of the new method, porous YB2C2 ceramics have been fabricated from Y2O3, BN and graphite powders for the first time. The as-prepared porous YB2C2 ceramics possess high porosity of 57.17%–75.26% and high compressive strength of 9.32–34.78 *** porosity, sintered density, radical shrinkage and compressive strength of porous YB2C2 ceramics can be controlled simply by changing the green density. Due to utilization of graphite as the carbon source, the porous YB2C2 ceramics show anisotropy in microstructure and mechanical behavior. These features render the porous YB2C2 ceramics promising as a thermal-insulating light-weight component for transpiration cooling system.

关键词： Ultrahigh temperature ceramics(UHTCs) YB2C2 Porous ceramics Microstructure Strength