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Solid solution evolution during mechanical alloying in Cu–Nb–Al compounds

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International Journal of Minerals,Metallurgy and Materials 2019年第9期26卷 1129-1139页

作者： Kaouther Zaara Mahmoud Chemingui Virgil Optasanu Mohamed Khitouni Laboratory of Inorganic Chemistry UR 11-ES-73University of SfaxB.P. 1171Sfax 3018Tunisia ICB UMR 6303 CNRSUniversity of Bourgogne Franche Comté9 av. Alain Savary21078 Dijon CedexFrance

This work concerns the structural evolution of Cu70Nb20Al10(at%) alloy processed by mechanical alloying using a planetary ball mill in air atmosphere for different times(4 to 200 h). The morphological, structural, microstructural, and thermal behaviors of the alloy were investigated by scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and differential scanning calorimetry. X-ray diffraction patterns were examined using the Rietveld refinement technique with the help of the MAUD software. A disordered FCC-Cu(Nb,Al) solid solution was formed after 8 h of milling. The crystallite size, microstrain, and lattice parameter were determined by the Rietveld method. With increasing milling time, the crystallite size of the final product-ternary-phase FCC-Cu(Nb,Al)-is refined to the nanometer scale, reaching 12 nm after 200 h. This crystallographic structure combines good mechanical strength and good ductility. An increase in microstrain and partial oxidation were also observed with increasing milling time.

关键词： powder metallurgy mechanical alloying nanomaterials copper-based alloy solid solution

Electronic and mechanical responses of two-dimensional HfS2,HfSe2,ZrS2,and ZrSe2 from first-principles

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Frontiers of Structural and Civil Engineering 2019年第2期13卷 486-494页

作者： Mohammad SALAVATI Institute of Structural Mechanics Bauhaus-Universitat WeimarD-99423 WeimarGermany

During the last decade, numerous high-quality two-dimensional (2D) materials with semiconducting electronic character have been synthesized. Recent experimental study (Sci. Adv. 2017;3: el700481) nevertheless confirmed that 2D ZrSe2 and HfSe2 are among the best candidates to replace the silicon in nanoelectronics owing to their moderate band-gap. We accordingly conducted first-principles calculations to explore the mechanical and electronic responses of not only ZrSe2 and HfSe2, but also ZrS? and HfS? in their single-layer and free-standing form. We particularly studied the possibility of engineering of the electronic properties of these attractive 2D materials using the biaxial or uniaxial tensile loadings. The comprehensive insight provided concerning the intrinsic properties of HfS2, HfSe2, ZrS2, and ZrSc? can be usefiil for their future applications in nanodevices.

关键词： 2D materials mechanical electronic DFT

Modeling of the mechanical Properties of Blend Based Polymer Nanocomposites Considering the Effects of Janus Nanoparticles on Polymer/Polymer Interface

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Chinese Journal of Polymer Science 2019年第2期37卷 164-177页

作者： Esmail Sharifzadeh Department of Chemistry Payame Noor University

Blend based polymer nanocomposites, comprising Janus nanoparticles at their polymer/polymer interface, were analytically/experimentally evaluated. The modeling procedure was performed in two stages: first, modeling of polymer/polymer interface region comprising Janus nanoparticles and second, modeling of the entire systems as a function of the variation of the blend *** the first stage, the modeling procedure was performed based on the development of the model proposed by Ji et al. and in the second stage, the fundamental of Kolarik's model was used in order to propose a developed and more practical model. It was shown that Janus nanoparticles may form dual polymer/particle interphase at polymer/polymer interface which can drastically affect the final mechanical properties of the system. Comparing the results of tensile tests imposed on different prepared samples with the predictions of the model proved its accuracy and reliability(error < 9%).

关键词： Blend based polymer nanocomposites Janus nanoparticles Modeling of mechanical properties

Experimental study on dynamic mechanical property of cemented tailings backfill under SHPB impact loading

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International Journal of Minerals,Metallurgy and Materials 2019年第4期26卷 404-416页

作者： Yu-ye Tan Xin Yu Davide Elmo Lin-hui Xu Wei-dong Song Key Laboratory of High-Efficient Mining and Safety of Metal Mines (Ministry of Education of China) University of Science and Technology Beijing School of Civil and Resources Engineering University of Science and Technology Beijing Norman B.Keevil Institute of Mining Engineering Applied Science SchoolUniversity of British Columbia

Cemented tailings backfill(CTB) have increasingly been used in recent years to improve the stability of mining stopes in deep underground mines. Deep mining processes are often associated with rock bursting and high-speed dynamic loading conditions. Therefore, it is important to investigate the characteristics and dynamic mechanical behavior of CTB. This paper presents the results of dynamic tests on CTB specimens with different cement and solid contents using a split Hopkinson pressure bar(SHPB). The results showed that some CTB specimens exhibited one to two lower stress peaks after reaching dynamic peak stress before they completely failed. The greater the cement-to-tailings ratio is, the more obvious the strain reaction. This property mainly manifested as follows. First,the dynamic peak stress increased with the increase of the cement-to-tailings ratio when the impact velocity was fixed. Second, the dynamic peak stress had a quadratic relationship with the average stress rate. Third, the cement-to-tailings ratio could enhance the increase rate of dynamic peak stress with strain rate. In addition, the dynamic strength enhancement factor K increased with the increase of strain rate, and its value was larger than that of the rock samples. The failure modes of CTB specimens under low-speed impact were tensile failure and X conjugate shear failure, where were nearly the same as those under static uniaxial and triaxial compression. The CTB specimens were crushed and broken under critical strain, a failure mode similar to that of low-strength concrete. The results of the experimental research can improve the understanding of the dynamic mechanical properties of CTB and guide the strength design of deep mining backfills.

关键词： impact loading test cemented tailings backfill dynamic mechanical properties split Hopkinson pressure bar

High temperature mechanical retention characteristics and oxidation behaviors of the MoSi2（Cr5Si3）–RSiC composites prepared via a PIP-AAMI combined process

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Journal of Advanced Ceramics 2019年第2期8卷 196-208页

作者： Peng-zhao GAO Lei CHENG Zheng YUAN Xiao-pan LIU Han-ning XIAO College of Materials Science and Engineering Hunan UniversityChangsha 410082China Hunan Province Key Laboratory for Advanced Carbon Materials and Applied Technology Hunan UniversityChangsha 410082China Hunan Province Key Laboratory for Spray Deposition Technology and Application Hunan UniversityChangsha 410082China

In the present paper,MoSi2(Cr5Si3)–RSiC composites were prepared via a combination of precursor impregnation pyrolysis(PIP) and MoSi2-Si-Cr alloy active melt infiltration(AAMI) process. Composition, microstructure, mechanical retention characteristics, and oxidation behaviors of the composites at elevated temperature were studied. X-ray diffraction(XRD) pattern confirms that the composites mainly compose of 6 H–SiC, hexagonal MoSi2, and tetragonal Cr5Si3. Scanning electron microscopy(SEM) image reveals that nearly denseMoSi2(Cr5Si3)–RSiC composites exhibiting three-dimensionally(3D) interpenetrated network structure are obtained when infiltrated at 2173 K, and the interface combination of the composites mainly depends on the composition ratio of infiltrated phases. Oxidation weight gain rate of the composites is much lower than that of RSiC matrix, where MoSiCr2 possesses the lowest value of 0.1630 mg×cm-2, about 78% lower than that of RSiC after oxidation at 1773 K for 100 h. Also, it possesses the highest mechanical values of 139.54 MPa(flexural strength σf and RT) and 276.77 GPa(elastic modulus Ef and RT), improvement of 73.73% and 29.77% as compared with that of RSiC, respectively. mechanical properties of the composites increase first and then decrease with the extension of oxidation time at 1773 K, due to the cooperation effect of surface defect reduction via oxidation reaction and thermal stress relaxation in the composites, crystal growth, and thickness increase of the oxide film. Fracture toughness of MoSiCr2 reaches 2.24 MPa·m1/2(1673 K), showing the highest improvement of 31.70% as compared to the RT value.

关键词： MoSi2(Cr5Si3)–RSiC composites precursor impregnation pyrolysis and MoSi2-Si-Cr alloy active melt infiltration (PIP-AAMI) high temperature mechanical characteristic oxidation behavior

Enhancing mechanical properties and air permeability of corundum porous materials by in situ formation of LaAl11O18 in bonding phase

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Journal of Rare Earths 2020年第2期38卷 195-202页

作者： Xin Xiong Zhoufu Wang Xitang Wang Hao Liu Yan Ma The State Key Laboratory of Refractories and Metallurgy Wuhan University of Science and TechnologyWuhan 430081China

Corundum porous materials of particle-packing type with different contents of in situ formed LaAl11O18were prepared using tabular corundum,reactive alumina and La2O3 powder as raw *** effects of the introduction of LaAl11O18 on the *** composition and properties of the porous materials were *** specimens were characterized by scanning electron microscopy.X-ray diffraction and mercury *** show that platelet-like LaAl11O18 is formed in situ by the reactions of La2O3 and *** a certain amount of La2O3 *** cold crushing strength,cold modulus of rupture and hot modulus of rupture(1400 x 0.5 h) of the specimens are increased,and the air permeability is improved *** further increasing the amount of La2O3 added,the mechanical properties and air permeability of the porous materials then decrease gradually owing to the increased numbers of pores and cracks in the bonding *** enhanced mechanical properties of the specimens with La2O3 added are attributed to the strengthening effects of plate-like LaAl11O18 in the bonding phase and to the activated sintering of both Al2O3 powder and corundum coarse aggregate for the diffusion of La3+in Al2O3 *** addition,the improved air permeability of the specimens should be related to the decreased content of pores in the bonding phase and the reduced number of interfacial cracks.

关键词： Porous materials of particle-packing type Lanthanum hexaluminate mechanical strength Strengthening mechanism Air permeability Rare earths

Molecular dynamics investigation of mechanical properties of single-layer phagraphene

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Frontiers of Structural and Civil Engineering 2019年第2期13卷 495-503页

作者： Ali Hossein Nezhad SHIRAZI Institute of Structural Mechanics Bauhaus-Universitat WeimarWeimarGermany

Phagraphene is a very attractive two-dimensional (2D) full carbon allotrope with very interesting mechanical, electronic, optical, and thermal properties. The objective of this study is to investigate the mechanical properties of this new graphene like 2D material. In this work, mechanical properties of phagraphene have been studied not only in the defect-free form, but also with the critical defect of line cracks, using the classical molecular dynamics simulations. Our study shows that the pristine phagraphene in zigzag direction experience a ductile behavior under uniaxial tensile loading and the nanosheet in this direction are less sensitive to temperature changes as compared to the armchair direction. We studied different crack lengths to explore the in fluence of defects on the mechanical properties of phagraphene. We also investigated the temperature effect on the mechanical properties of pristine and defective phagraphene. Our classical atomistic simulation results confirm that larger cracks can reduce the strength of the phagraphene. Moreover, it was shown the temperature has a considerable weakening effect on the tensile strength of phagraphene. The results of this study may be useful for the design of nano-devices using the phagraphene.

关键词： phaqraphene mechanical properties crack propagation molecular dynamics thermal effects

Microstructure and mechanical properties of friction stir welding joint during post weld heat treatment with different zigzag lines

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Rare Metals 2019年第11期38卷 1070-1077页

作者： Zhi-Li Hu Qiu Pang Ming-Liang Dai Hubei Key Laboratory of Advanced Technology of Automobile Components Wuhan University of TechnologyWuhan 430070China Hubei Collaborative Innovation Center for Automotive Components Technology Wuhan University of TechnologyWuhan 430070China School of mechanical and Electrical Engineering Wuhan Donghu UniversityWuhan 430212China

Zigzag line is a common defect in friction stir welding(FSW) *** formation mechanism of the zigzag line in Al-Cu alloy FSW joint and its influence on the microstructure and mechanical properties during post weld heat treatment(PWHT) were studied by scanning electron microscopy(SEM),microhardness and tensile *** is found that the occurrence of zigzag line for PWHT joint is determined by PWHT process which in nature depends on residual stress and thermal stress of FSW *** optimization of PWHT process to reduce the residual and thermal stress can trigger for the deterioration of mechanical properties of PWHT joints with zigzag *** obvious decrease of tensile properties is observed for T6-450 and T6-495 joints although zigzag line appears in the *** determines the sizes of zigzag line cracks and consequently determines the fracture location and characteristics of FSW joint.

关键词： Friction stir welding Post weld heat treatment Zigzag line mechanical properties

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