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Processing, microstructure and mechanical Properties of Ti6Al4V Particles-Reinforced mg matrix Composites

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Acta metallurgica Sinica(English Letters) 2016年第10期29卷 940-950页

作者： X.m.Wang X.J.Wang X.S.Hu K.Wu m.y.zheng School of materials Science and Engineering Harbin Institute of Technology

Novel Ti6Al4V particles-reinforced AZ91 mg matrix composites were successfully fabricated by stir casting method. The stirring time in semisolid condition directly affected the particle distribution and the quality of the ingots. Furthermore, the optimal speed of the heating and the liquid stirring could overcome particle settlement caused by the density difference between the matrix and the particles. Ti6Al4V particles distributed uniformly in the composites with different particle contents. The average grain size decreased with the increase in the particle contents. The Ti6A14V particles bonded pretty well with the alloy matrix. In addition, there were some interfacial reactions in the composites. There were rod-like A13Ti phases at the interface. The precipitates extended from the particle surface to the matrix, and they might improve the interfacial bonding strength. The ultimate tensile strength, yield strength and elastic modulus were enhanced as the particle contents increased, and the elongation was much better than that of the same matrix material reinforced with SiC particles. Thus, the novel composites exhibit better comprehensive mechanical properties.

关键词： magnesium matrix composites Ti6Al4V particles Stir casting microstructure mechanicalproperties

Role of extrusion rate on the microstructure and tensile properties evolution of ultrahigh-strength low-alloy mg-1.0Al-1.0Ca-0.4mn(wt.%)alloy

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Journal of magnesium and Alloys 2023年第2期11卷 553-561页

作者： X.Q.Liu X.G.Qiao R.S.Pei y.Q.Chi L.yuan m.y.zheng School of material Science and Engineering Harbin Institute of TechnologyHarbin 150001China Institut fur metallkunde und meterialphysik RWTH Aachen UniversityAachen D-52056Germany

mg-1.0Al-1.0Ca-0.4mn(AXm1104, wt.%) low alloy was extruded at 200 ℃ with an extrusion ratio of 25 and different ram speeds from 1.0 to 7.0 mm/s. The influence of extrusion rate on microstructure and mechanical properties of the AXm1104 alloy was systematically studied. With the increasing of extrusion rate, the mean dynamically recrystallized(DRXed) grain size of the low alloy and average particles diameter of precipitate second phases were increased, while the degree of grain boundary segregation and the intensity of the basal fiber texture were decreased. With the rising of extrusion rate from 1.0 to 7.0 mm/s, the tensile yield strength(TyS) of the as-extruded AXm1104 alloy was decreased from 445 mPa to 249 mPa, while the elongation to failure(EL) was increased from 5.0% to 17.6%. The TyS, ultimate tensile strength(UTS) and EL of the AXm1104 alloy extruded at the ram speed of 1.5 mm/s was 412 mPa, 419 mPa and 12.0%, respectively,exhibiting comprehensive tensile mechanical properties with ultra-high strength and excellent plasticity. The ultra-high TyS of 412 mPa was mainly due to the strengthening from ultra-fine DRXed grains with segregation of solute atoms at grain boundaries. The strain hardening rate is increase slightly with increasing extrusion speed, which may be ascribed to the increasing mean DRXed grain size with rising extrusion speed. The higher strain hardening rate contributes to the higher EL of these AXm1104 samples extruded at higher ram speed.

关键词： mg-Al-Ca-mn alloy Ultrafine grain Extrusion rate Grain boundary segregation microstructure Ultrahigh strength

Simultaneously Enhanced mechanical Properties and Damping Capacities of ZK60 mg Alloys Processed by multi-Directional Forging

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Acta metallurgica Sinica(English Letters) 2021年第2期34卷 265-277页

作者： L.B.Tong J.H.Chu D.N.Zou Q.Sun S.Kamado H.G.Brokmeier m.y.zheng School of metallurgical Engineering Xi'an University of Architecture and TechnologyXi'an 710055China School of materials Science and Engineering.Harbin Institute of Technology Harbin 150001China College of materials Science and Engineering.Jilin University Changchun 130025China Department of mechanical Engineering Nagaoka University of TechnologyNagaoka 940-2188Japan Institute of materials Science and Engineering Clausthal University of TechnologyAgricolastrasse 638678 Clausthal-Zellerfeld.Germany

In this study,the mechanical properties and damping capacities of cast mg-5.5 Zn-0.6 Zr(weight percent,ZK60)alloys have been simultaneously improved by a facile multi-directional forging(mDF)processing,and the mechanisms of microstructure evolution and texture modification are systematically *** activation of tension twinning occurs during the initial mDF stage,due to the coarse-grained structure of the as-cast *** increasing mDF passes,the continuous dynamic recrystallization(CDRX)results in a fine equiaxed-grain *** typical non-basal texture is formed in the as-mDFed alloy for 6 passes,with the(0001)planes inclined 60°–70°to forged direction and 10°–20°to transverse direction,respectively.A good balance between the strength(~194.9 mPa)and ductility(~24.9%)has been achieved,which can be ascribed to the grain refinement,non-basal texture and fine precipitate *** damping capacity is remarkably improved after mDF processing,because the severe deformation increases the dislocation density,which effectively enlarges the sweep areas of mobile dislocations.

关键词： mg alloy multi-directional forging microstructure Texture evolution mechanical properties Damping capacity

Development of a high-strength mg alloy with superior ductility through a unique texture modification from equal channel angular pressing

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Journal of magnesium and Alloys 2021年第3期9卷 1007-1018页

作者： L.B.Tong J.H.Chu W.T.Sun Z.H.Jiang D.N.Zou S.F.Liu S.Kamado m.y.zheng School of metallurgical Engineering Xi'an University of Architecture and TechnologyXi'an 710055China School of materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China School of materials Science and Engineering Jilin UniversityChangchun 130025China Department of mechanical Engineering Nagaoka University of TechnologyNagaoka 940-2188Japan

In the current study,a homogenous ultra-fine grained microstructure with average grain size of 1.0μm is achieved in the mg-Zn-Ca-mn alloy through the reduplicative equal channel angular pressing(ECAP)at 300℃,and the mechanical properties are remarkably improved,with room-temperature yield strength of 269.6 mPa and elongation of 22.7%.The twinning deformation results in a discontinuous recrystallization behavior in the initial stage of *** further deformation,the continuously dynamic recrystallization contributes to an obvious grain refinement *** activation of non-basal slip system leads to the formation of a unique basal texture,which is related to the elevated ECAP temperature and the decreased grain *** grain refinement and texture modification derived from ECAP process result in the increase of yield strength,while the cracked secondary phase particles are beneficial to the enhanced ductility,through reducing the stress concentration and hindering premature failure.

关键词： mg alloy ECAP microstructural evolution High strength Superior ductility

microstructure and room temperature tensile properties of 1μm-SiCp/AZ31B magnesium matrix composite

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Journal of magnesium and Alloys 2015年第2期3卷 155-161页

作者： m.J.Shen X.J.Wang m.F.Zhang B.H.Zhang m.y.zheng K.Wu College of Engineering Shenyang Agricultural UniversityShenyang 110866PR China School of materials Science and Engineering Harbin Institute of TechnologyHarbin 150001PR China Liaoning Provincial Gem Quality Supervision and Inspection Center Shenyang 110000PR China

In the present study,AZ31B magnesium matrix composites reinforced with two volume fractions(3 and 5 vol.%)of micron-SiC particles(1μm)were fabricated by semisolid stirring assisted ultrasonic vibration *** as-cast ingots were extruded at 350℃ with the extrusion ratio of 15:1 at a constant ram speed of 15 mm/*** microstructure of the composites was investigated by optical microscopy,scanning electron microscope and transmission electron *** characterization of the composites showed relative uniform reinforcement distribution and significant grain *** presence of 1μm-SiC particles assisted in improving the elastic modulus and tensile *** ultimate tensile strength and yield strength of the 5 vol.%SiCp/AZ31B composites were simultaneously improved.

关键词： magnesium matrix composite microstructure mechanical properties

Effect of forced-air cooling on the microstructure and age-hardening response of extruded mg-Gd-y-Zn-Zr alloy full with LPSO lamella

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Journal of materials Science & Technology 2021年第14期73卷 66-75页

作者： S.Z.Wu T.Nakata G.Z.Tang C.Xu X.J.Wang X.W.Li X.G.Qiao m.y.zheng L.Geng S.Kamado G.H.Fan School of materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China Research Center for Advanced magnesium Technology Nagaoka University of TechnologyNagaoka 940-2188Japan School of material Science and Engineering Harbin University of Science and TechnologyHarbin 150040China Key Laboratory for Light-weight materials Nanjing Tech UniversityNanjing 211816China

The homogenized mg-8.2 Gd-3.8 y-1.0 Zn-0.4 Zr(wt.%)alloy full of plate-shaped long period stacking ordered(LPSO)phases was hot extruded in the atmosphere and cooled by the forced-air,then the effect of forced-air cooling on the microstructure and age-hardening response of the alloy was investigated in this *** results show that in comparison with the extruded sample cooling in the atmosphere,the forced-air cooling restricts dynamic recrystallization(DRX)and brings about finer dynamic recrystallized(DRXed)grain size,stronger basal texture and higher dislocation ***,the forced-air cooling promotes the dynamic precipitation in the DRXed regions and facilitates formation of plate-shaped LPSO phases andγ’phases with smaller interspacing in the unrecrystallized(un DRXed)regions,then slightly restricts the precipitation ofβphases during *** peak-ageing treatment,the extruded sample with forced-air cooling shows superior tensile properties with a tensile yield strength of 439 mPa,an ultimate tensile strength of 493 mPa,and elongation to failure of 18.6%.

关键词： mg-RE alloy LPSO phase Dynamic recrystallization Precipitation mechanical properties

Reducing the tension-compression yield asymmetry of extruded mg-Zn-Ca alloy via equal channel angular pressing

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Journal of magnesium and Alloys 2015年第4期3卷 302-308页

作者： L.B.Tong m.y.zheng S.Kamado D.P.Zhang J.meng L.R.Cheng H.J.Zhang State Key Laboratory of Rare Earth Resources Utilization Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China School of materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China Department of mechanical Engineering Nagaoka University of TechnologyNagaoka 940-2188Japan

The influence of equal channel angular pressing on the tension-compression yield asymmetry of extruded mg-5.3 Zn-0.6 Ca(weight percent)alloy has been *** microstructure was obviously refined by the large strain during the equal channel angular pressing,accompanied with very fine Ca_(2)mg_(6)Zn_(3) phases with average diameter of 70 *** weak tension-compression yield asymmetry after equal channel angular pressing is mainly attributed to the reduced volume fraction of extension twinning during the compression,because the slope(k)of twinning in Hall-Petch relationship is higher than that of dislocation slip,and the twinning deformation is difficult to take place with decreasing grain *** basal slip is more active in the alloy after equal channel angular pressing,due to the non-basal texture components,which hinders the twinning activation and reduces the yield ***,the presence of fine precipitate restricts the twinning activation,which also contributes to the reduction of yield asymmetry.

关键词： mg-Zn-Ca alloy yield asymmetry Equal channel angular pressing Twinning Precipitates

Growth of RB Population in the Conversion Phase of Chlamydia Life Cycle

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Communications on Applied mathematics and Computation 2024年第1期6卷 90-112页

作者： Frederic y.m.Wan Department of mathematics University of CaliforniaIrvineCA92697-3875USA

Upon infecting a host cell,the reticulate body(RB)form of the Chlamydia bacteria simply proliferates by binary fission for an extended *** data show only RB units in the infected cells 20 hours post infection(hpi),spanning nearly half way through the development *** data collected every 4 hpi,conversion to the elementary body(EB)form begins abruptly at a rapid rate sometime around 24 *** modeling proliferation and conversion as simple birth and death processes,it has been shown that the optimal strategy for maximizing the total(mean)EB population at host cell lysis time is a bang-bang control qualitatively replicating the observed conversion ***,the simple birth and death model for the RB proliferation and conversion to EB deviates in a significant way from the available data on the evolution of the RB population after the onset of RB-to-EB *** working with a more refined model that takes into account a small size threshold eligibility requirement for conversion noted in the available data,we succeed in removing the deficiency of the previous models on the evolution of the RB population without affecting the optimal bang-bang conversion strategy.

关键词： Chlamydia Life cycle Optimal control maximal infectious spread Specie competitive survival

A Collocation Technique via Pell-Lucas Polynomials to Solve Fractional Differential Equationmodel for HIV/AIDS with Treatment Compartment

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Computer modeling in Engineering & Sciences 2024年第10期141卷 281-310页

作者： Gamze yıldırım Suayip yüzbası Department of mathematics Faculty of ScienceAkdeniz UniversityAntalya07058Turkey Department of mathematics Faculty of Basic ScienceGebze Technical UniversityKocaeli41400Turkey Department of mathematics Faculty of ScienceBartın UniversityBartın74100Turkey

In this study,a numerical method based on the Pell-Lucas polynomials(PLPs)is developed to solve the fractional order HIV/AIDS epidemic model with a treatment *** HIV/AIDS mathematical model with a treatment compartment is divided into five classes,namely,susceptible patients(S),HIV-positive individuals(I),individuals with full-blown AIDS but not receiving ARV treatment(A),individuals being treated(T),and individuals who have changed their sexual habits sufficiently(R).According to the method,by utilizing the PLPs and the collocation points,we convert the fractional order HIV/AIDS epidemic model with a treatment compartment into a nonlinear system of the algebraic ***,the error analysis is presented for the Pell-Lucas approximation *** aim of this study is to observe the behavior of five populations after 200 days when drug treatment is applied to HIV-infectious and full-blown AIDS *** demonstrate the usefulness of this method,the applications are made on the numerical example with the help of *** addition,four cases of the fractional order derivative(p=1,p=0.95,p=0.9,p=0.85)are examined in the range[0,200].Owing to applications,we figured out that the outcomes have quite decent ***,we understand that the errors decrease when the value of N *** figures in this study are created in *** outcomes indicate that the presented method is reasonably sufficient and correct.

关键词： Collocation method fractional differential equations HIV/AIDS epidemic model Pell-Lucas polynomials