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Effect of Particle Size on Mechanical Properties and fracture behaviors of Age-Hardening SiC/Al–Zn–Mg–Cu Composites

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Acta Metallurgica Sinica(English Letters) 2021年第10期34卷 1447-1459页

作者： Guonan Ma Dong Wang Bolv Xiao Zongyi Ma Institute of Metal Research Chinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China

15 vol.% SiC/Al-6.5Zn-2.8 Mg-1.7 Cu(wt%) composites with varying particle sizes(3.5, 7.0, 14 and 20 μm), i.e., C-3.5, C-7.0, C-14, and C-20, respectively, were fabricated by powder metallurgy(PM) method and subjected to microstructural examination. The effect of particle size on mechanical properties and fracture behaviors of the T6-treated composites was revealed and analyzed in detail. Element distribution and precipitates variations in the composites with varying particle sizes were emphatically considered. Results indicated that both tensile strength and plasticity of the T6-treated composites increased first and then decreased with particle size decreasing. The C-7.0 composite simultaneously exhibited the highest ultimate tensile strength(UTS) of 686 MPa and best elongation(El.) of 3.1%. The smaller-sized SiC particle would introduce more oxide impurities, which would react with the alloying element in the matrix to cause Mg segregation and depletion. According to strengthening mechanism analysis, the weakening of precipitation strengthening in the T6-treated C-3.5 composite was the main cause of the lower tensile strength. Additionally, the larger SiC particle, the more likely to fracture, especially in the composites with high yield strength. For the T6-treated C-20 composites, more than 75% SiC particles were broken up, resulting in the lowest plasticity. As decreasing particle size, the fracture behaviors of the T6-treated composites would change from particle fracture to matrix alloy fracture gradually.

关键词： Metal matrix composites Mechanical properties Particle size fracture behaviors Strengthening mechanisms

Influences of boron contents on microstructures and mechanical properties of as-casted nearαtitanium alloy

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Journal of Materials Science & Technology 2021年第18期77卷 1-18页

作者： Xiaozhao Ma Zhilei Xiang Chao Tan Zhitian Wang Yingying Liu Ziyong Chen Qun Shu College of Materials Science and Engineering.Beijing University of Technology Beijing 100124China Aviation Industry of China(AVIC)Manufacture Technology Institute Beijing 100024China

Ti-6.5 Al-2.5 Sn-9 Zr-0.5 Mo-0.25 Si-1 Nb-1 W-0.1 Er-x B(x=0,0.1,0.2,0.4,0.6 and 0.8 wt%)with different boron contents are fabricated for *** of boron element and its amounts on phase constitutions,microstructures,textures and compression mechanical properties are carefully *** the increasing boron additions,contents of TiB phase increase,and the maximum intensities of textures *** are significantly and continuously refined after adding boron element and with the increasing boron additions,and turning point of refinement rates for different microstructural parameters is found at 0.2 wt%boron *** increase monotonously,while elongations increase firstly and decrease *** maximum value of elongation is acquired at boron content of 0.2 wt%.On the premise of ensuring plasticity,0.2 wt%boron content is the most appropriate amount for microstructural refinement and mechanical properties enhancement for current nearαtitanium ***,aspect ratios of TiB whiskers increase with the increasing boron *** of near equiaxedαgrains orαgrains with irregular morphologies are discovered around TiB *** and twistedαgrain boundaries are also obviously detected in boron containing ***,premature fracture of alloys containing TiB whiskers is largely influenced by the fracture of these brittle reinforcements.

关键词： Boron element Mechanical properties Microstructures fracture behaviors Nearαtitanium alloy Textures

Rock damage and fracturing induced by high static stress and slightly dynamic disturbance with acoustic emission and digital image correlation techniques

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第5期13卷 1002-1019页

作者： Shuting Miao Peng-Zhi Pan Petr Konicek Peiyang Yu Kunlun Liu State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China University of Chinese Academy of Sciences Beijing100049China Department of Geomechanics and Mining Research Institute of Geonics of the Czech Academy of SciencesOstrava70800Czech Republic Shenhua Xinjiang Energy Company Limited Urumqi830027China

A series of coupled static-dynamic loading tests is carried out in this study to understand the effect of slightly dynamic disturbance on the rocks under high static *** acoustic emission(AE)and digital image correlation(DIC)techniques are combined to quantitatively characterize the damage and fracturing behaviors of *** effects of three influencing factors,*** static stress,disturbance amplitude,and disturbance frequency,on the damage and fracturing evolution are *** experimental results reveal the great differences in AE characteristics and fracturing behaviors of rocks under static loads and coupled static-dynamic *** the Kaiser effect and Felicity effect are observed during the disturbance loading *** crack initiation,stable and unstable propagation in the highly-stressed rocks can be triggered by cyclic disturbance loads,and more local tensile splitting cracks are found in the rocks subjected to coupled static-dynamic *** damage and fracturing evolution of rocks during cyclic disturbances can be divided into two stages,*** and accelerated stages,and the increase rate and proportion of each stage are greatly affected by these influencing *** initial static stress,low disturbance frequency,and high disturbance amplitude are considered to be adverse factors to the stability of the rocks,which would induce a high increase rate of the steady stage and a high proportion of the accelerated stage within the whole disturbance *** on the two-stage damage evolution trend,a linear-exponential damage model is employed to predict the instability of the rocks under coupled static-dynamic loads.

关键词： Damage evolution fracture behaviors High static stress Dynamic disturbance Damage model

fracture Behavior of CrN Coatings Under Indentation and Dynamic Cycle Impact

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Journal of Wuhan University of Technology(Materials Science) 2012年第3期27卷 411-414页

作者：田林海唐宾 Research Institute of Surface Engineering Taiyuan University of Technology

fracture behavior of CrN coatings deposited on the surface of silicon and AISI52100 steel by different energy ion beam assisted magnetron sputtering technique （IBAMS） was studied using indentation and dynamic cycle impact. It is found that, for the coatings on silicon substrate, the cracks form in the indentation corners and then propagate outward under Vickers indentation. The coating prepared using ion assisted energy of 800 eV shows the highest fracture resistance due to its compact structure. Under Rockwell indentation, only finer radial cracks are found in the CrN coating on AISI 52100 steel without ion assisting while in the condition of ion assisting energy of 800 eV, radial, lateral cracks and spalling appear in the vicinity of indentation. The fracture of CrN coatings under dynamic cycle impact is similar to fatigue. The impact fracture resistance of CrN coatings increases with the increase of ion assisting energy.

关键词： CrN coatings IBAMS fracture behaviors indentation dynamic cycle impact