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Y_5Si_3C and Y_3Si_2C_2: Theoretically predicted MAX phase like damage tolerant ceramics and promising interphase materials for SiC_f/SiC composites

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Journal of Materials Science & Technology 2019年第3期35卷 313-322页

作者： Yanchun Zhou Huimin Xiang fu-zhi dai Science and Technology on Advanced functional Composite Laboratory Aerospace Research Institute of Materials & Processing Technology

Researching for interphase materials that can protect SiC fibers from oxygen and water vapor attacks has become one of the most important issues for the applications of SiC_f/SiC composites in high-temperature combustion environment. However, such kinds of interphase materials are not available yet. Herein,we report theoretically predicted properties of two promising interphase materials Y_5Si_3 C and Y_3Si_2C_*** crystallizing in different structures, they share the common features of layered structure,anisotropic chemical bonding, anisotropic electrical and mechanical properties, and low shear deformation resistance. The bulk moduli for Y_5Si_3C and Y_3Si_2C_2 are 78 and 93 GPa, respectively; while their shear moduli are 52 and 50GPa, respectively. The maximum to minimum Young's modulus ratios are1.44 for Y_5Si_3C and 3.27 for Y_3Si_2C_2. Based on the low shear deformation resistance and low Pugh's ratios(G/B = 0.666 forY_5Si_3C and 0.537 for Y_3Si_2C_2; G: shear modulus; B: bulk modulus), they are predicted as damage tolerant and soft ceramics with predicted Vickers hardness of 9.6 and 6.9 GPa, *** cleavage plane and possible slip systems are(000 l) and(0001)[1120] and(1010)[0001] forY_5Si_3C,and those for Y_3Si_2C_2 are {h00} and(010)[101]. Since the oxidation products are water-vapor resistant Y2 Si2 O7, Y2 SiO5 and/or Y_2 O_3 upon oxidation, and the volume expansions are ca 140% and ca 26% for Y_5Si_3C and Y_3Si_2C_2, they are expected to seal the interfacial cracks in SiC_f/SiC composites. The unique combination of easy cleavage, low shear deformation resistance, volume expansions upon oxidation, and the resistance of the oxidation products to water vapor attack warrant them promising as interphase materials of SiC_f/SiC composites for water-vapor laden environment applications.

关键词： Y5Si3C Y3Si2C2 Interphase material Damage tolerant ceramics Electronic structure

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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

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Faceted interfaces: a key feature to quantitative understanding of transformation morphology

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npj Computational Materials 2016年第1期2卷 44-57页

作者： Wen-Zheng Zhang Xin-fu Gu fu-zhi dai School of Materials Science and Engineering Tsinghua UniversityBeijingChina Institute for Materials Research Tohoku UniversitySendaiJapan Science and Technology on Advanced functional Composite Laboratory Aerospace Research Institute of Materials and Processing TechnologyBeijingChina

Faceted interfaces are a typical key feature of the morphology of many microstructures generated from solid-state phase ***,prediction and simulation of this faceted morphology remain a challenge,especially for systems where irrational orientation relationships(ORs)between two phases and irrational interface orientations(IOs)are *** terms of structural singularities,this work suggests an integrated framework,which possibly encompasses all candidates of faceted *** structural singularities are identified from a matching pattern,a dislocation structure and/or a ledge *** resultant singular interfaces have discrete IOs,described with low-index g’s(rational orientations)and/orΔg’s(either rational or irrational orientations).Various existing models are grouped according to their determined results regarding the OR and IO,and the links between the models are clarified in the integrated *** of defect types as far as possible in a dominant singular interface often exerts a central restriction on the *** irrational IO is usually due to the elimination of dislocations in one direction,i.e.,an O-line *** methods using both three-dimensional and two-dimensional models for quantitative determinations of O-line interfaces are reviewed,and a detailed example showing the calculation for an irrational interface is *** association between structural singularities and local energy minima is verified by atomistic calculations of interfacial energies in fcc/bcc alloys where it is found that the calculated equilibrium cross-sections are in a good agreement with observations from selected alloys.

关键词： transformation rational interface

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Structures and energetics of semicoherent interfaces of precipitates in hcp/bcc systems:A molecular dynamics study

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Journal of Materials Science & Technology 2021年第8期67卷 50-60页

作者： Jin-Yu Zhang fu-zhi dai zhi-Peng Sun Wen-Zheng Zhang Key Laboratory of Advanced Materials(MOE) School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China Science and Technology of Advanced functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of ChinaChengdu 610041China

α/β(hcp/bcc)interfaces are of great importance in the microstructure development and the mechanical properties of titanium and zirconium *** work contributes to the study of interface energetics and interfacial structures of the precipitate in the hcp/bcc system based on a simulation study using molecular statics(MS)and molecular dynamics(MD).The input orientation relationship(OR)was calculated based on the O-line *** on the energy of the interfaces containing the invariant line(IL),two preferred facets were determined by the Wulff construction,which explained the observed orientations of the habit plane(HP)and the side facet(SF).The deviation of the observed precipitate morphology from the equilibrium shape was discussed in terms of interface *** structures of the interfaces surrounding a three-dimensional(3 D)precipitate,including the preferred facets and the end face,were obtained at the atomic *** simulated dislocation structures and atomic structures in these interfaces are in good agreement with those of the experimental observations for Ti-Cr alloys.A method was suggested for modifying the O-cell structure with the guidance of the relaxed structure,yielding consistency between the calculated dislocation structure based on the generalized O-element approach and the simulation results.

关键词： Interface Misfit dislocation Precipitate

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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

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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

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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

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Segregation of solute atoms in ZrC grain boundaries and their effects on grain boundary strengths

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Journal of Materials Science & Technology 2022年第6期101卷 234-241页

作者： fu-zhi dai Yinjie Sun Yixiao Ren Huimin Xiang Yanchun Zhou Science and Technology on Advanced functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China

ZrC is a promising candidate for the application in ultra-high temperature regime due to its unique combination of excellent properties,such as high melting point,good chemical inertness and high temperature *** rapid decrease of strength at high temperatures,however,is one of the obstacles that impedes its practical *** of grain boundaries by solute segregation is believed to be an effective way to improve its high temperature ***,the segregation tendency of ten solid solute atoms,including Sc,Ti,V,Cr,Y,Nb,Mo,Hf,Ta,W,in Zr C grain boundaries,and the strengthening/weakening effects on grain boundaries due to segregation are investigated by first-principles *** segregation tendency is found dominated by the size effect,which is confirmed by both a qualitative analysis and a quantitative approach based on support vector *** means that big atoms tend to segregate to grain boundary sites with local expansions,while small atoms tend to segregate to grain boundary sites with local *** on stress-strain responses indicate that segregation of small atoms(Ti,V,Cr,Nb,Ta,Mo,W)can usually improve grain boundary strengths by inducing compression strains to grain boundaries,even though there is also an *** contrast,segregation of Sc and Y will soften grain *** results reveal that strengthening of grain boundaries by solute segregation is a valuable avenue to enhance high temperature mechanical properties of ZrC,providing guidelines for further design of ZrC based materials.

关键词： ZrC Grain boundary Segregation Strength First-principles calculation Machine learning

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Temperature Dependent Thermal and Elastic Properties of High Entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))B_(2):Molecular Dynamics Simulation by Deep Learning Potential

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Journal of Materials Science & Technology 2021年第13期72卷 8-15页

作者： fu-zhi dai Yinjie Sun Bo Wen Huimin Xiang Yanchun Zhou Science and Technology on Advanced functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing100076China

High entropy diborides are new categories of ultra-high temperature ceramics,which are believed promising candidates for applications in hypersonic ***,knowledge on high temperature thermal and mechanical properties of high entropy diborides is still lacking unit *** this work,variations of thermal and elastic properties of high entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))B_(2) with respect to temperature were predicted by molecular dynamics ***,a deep learning potential for Ti-Zr-Hf-Nb-Ta-B diboride system was fitted with its prediction error in energy and force respectively being 9.2 meV/atom and 208 meV/A,in comparison with first-principles ***,temperature dependent lattice constants,anisotropic thermal expansions,anisotropic phonon thermal conductivities,and elastic properties of high entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))B_(2) from 0℃to 2400℃were evaluated,where the predicted room temperature values agree well with experimental *** addition,intrinsic lattice distortions of(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))B_(2) were analyzed by displacements of atoms from their ideal positions,which are in an order of 10^(-3) A and one order of magnitude smaller than those in(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))*** indicates that lattice distortions in(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))B_(2) is not so severe as *** the new paradigm of machine learning potential,deep insight into high entropy materials can be achieved in the future,since the chemical and structural complexly in high entropy materials can be well handled by machine learning potential.

关键词： High entropy diborides Machine learning potential Thermal properties Elastic properties Molecular dynamics

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Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

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Acta Metallurgica Sinica(English Letters) 2019年第6期32卷 669-676页

作者： zhi-Peng Sun fu-zhi dai Ben Xu Wen-Zheng Zhang Key Laboratory of Advanced Materials(MOE) School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China Science and Technology of Advanced functional Composite Laboratory Aerospace Research Institute of Materials and Processing TechnologyBeijing 100076China

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix *** a key feature of microstructure,the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial *** letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics *** found that the ferrite grain tends to grow into an elongated plate-like shape,independent of its initial confi *** fi nal shape of the ferrite is closely related to the misfi t between the two phases,with the longest direction and the broad facet of the plate being,respectively,consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC)*** strain energy calculation in the framework of Eshelby’s inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically *** is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.

关键词： Coherent ferrite Anisotropic growth Molecular dynamics simulation Burgers vector content Eshelby’s inclusion theory

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