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  • Serration and Noise Behavior in Advanced Materials
  • A Brief Review of High Entropy Alloys and Serration Behavior and Flow Units
  • Multicomponent alloys with high entropy of mixing,e.g.,high entropy alloys(HEAs)and/or multiprincipal-element alloys(MEAs),are attracting increasing attentions,because the materials with novel properties are being developed,based on the design strategy of the equiatomic ratio,multicomponent,and high entropy of mixing in their liquid or random solution state.Recently,HEAs with the ultrahigh strength and fracture toughness,excellent magnetic properties,high fatigue,wear and corrosion resistance,great phase stability/high resistance to heat-softening behavior,sluggish diffusion effects,and potential superconductivity,etc.,were developed.The HEAs can even have very high irradiation resistance and may have some self-healing effects,and can potentially be used as the first wall and nuclear fuel cladding materials.Serration behaviors and flow units are powerful methods to understand the plastic deformation or fracture of materials.The methods have been successfully used to study the plasticity of amorphous alloys(also bulk metallic glasses,BMGs).The flow units are proposed as:free volumes,shear transition zones(STZs),tension-transition zones(TTZs),liquid-like regions,soft regions or soft spots,etc.The flow units in the crystalline alloys are usually dislocations,which may interact with the solute atoms,interstitial types,or substitution types.Moreover,the flow units often change with the testing temperatures and loading strain rates,e.g.,at the low temperature and high strain rate,plastic deformation will be carried out by the flow unit of twinning,and at high temperatures,the grain boundary will be the weak area,and play as the flow unit.The serration shapes are related to the types of flow units,and the serration behavior can be analyzed using the power law and modified power law.
  • Self-organized Criticality Behavior in Bulk Metallic Glasses
  • Serrated flows are known as repeated yielding of bulk metallic glasses(BMGs)during plastic deformation under different loading conditions,which are associated with the operation of shear banding.According to the statistics of some parameters,the shear avalanches can display a self-organized critical state,suggesting a large ductility of BMGs.The emergence of the self-organized criticality(SOC)behavior in different BMGs is due to the temperature,strain rate,and chemical compositions.The SOC behavior is accompanied with the following phenomena:the interactions occur in the shear bands;the incubation time is longer than the relaxation time;the time interval is lacking of typical time scale;and the spatial or temporal parameters should display apower-law distribution.
  • Microstructure Evolution and Mechanical Properties of Spray-deposited Al-21.47Si-4.73Fe-2.5Cu-0.9Mg Alloy
  • Al-Si-Fe-Cu-Mg alloy was prepared by spray deposition and was further processed by hot extrusion as well as T6heat-treatment.The results indicate that the microstructure of the deposited alloy is composed of primary Si particles with average size of less than 5μm,α-Al,Al2CuMg,β-Al5FeSi andδ-Al4FeSi2(rectangular shape),and no eutectic silicon is found due to the special solidification behavior.The age hardening curves reveal two peaks.The uniform ultimate tensile strength(UTS)and the elongation of the peak-aged Al-Si-Fe-Cu-Mg alloy are 468.3 MPa,0.61% at 298 Kand 267.4MPa,6.42% at 573 K,respectively.The fracture surfaces display brittle fracture morphology at 298 K,whereas it varies to mixture of brittle and ductile failure with increasing the temperature.
  • Insight on Viscoelasticiy of Ti_(16.7)Zr_(16.7)Hf_(16.7)Cu_(16.7)Ni_(16.7)Be_(16.7)High Entropy Bulk Metallic Glass
  • High entropy bulk metallic glasses show promising mechanical and physical properties.Dynamic mechanical properties of Ti16.7Zr16.7Hf16.7Cu16.7Ni16.7Be16.7high entropy bulk metallic glass were investigated by mechanical spectroscopy(or called dynamic mechanical analysis).The main(α)relaxation was observed in the framework of the loss modulus G″,which is related to the dynamic glass transition behaviour for the glassy materials.From physical model point of view,dynamic mechanical properties of the Ti16.7Zr16.7Hf16.7Cu16.7Ni16.7Be16.7high entropy bulk metallic glass show good agreement compared with the quasi-point defects theory.
  • Rate Dependence of Serrated Flow and Its Effect on Shear Stability of Bulk Metallic Glasses
  • The rate dependence of serrated flow and its effects on the stability of shear banding were systematically investigated in a prototypic bulk metallic glass.It was found that with the increase of external strain rate,the serrated flow is gradually suppressed and could completely disappear at a critical strain rate.The serration size,characterized by the mean stress drop amplitude,decreases inversely with the strain rate,while the waiting time for serration decreases with the strain rate in a power-law manner.The rate dependence of the serrated flow has important effects on the dynamics and stability of shear banding process,and leads to an optimal plasticity achieved around the critical strain rate for the disappearance of serrated flow.These results are discussed and interpreted in terms of the microscopic deformation theory and the stick-slip dynamics of shear banding for bulk metallic glasses.
  • Influence of Zn Addition on Microstructures and Martensitic Transformation in CuZr-based Alloys
  • Compositional dependences on microstructures and martensitic transformation behaviors in(Cu0.5Zr0.5)100-xZnx(x=1.5,2.5,4.5,7.0,10.0,and 14.0at.%)alloys were investigated.It was found that CuZr martensites were present in the present alloys.With increasing Zn content,the volume fractions of CuZr martensitic crystals and B2 CuZr phase gradually decrease and increase,respectively.With the addition of high Zn contents(i.e.,7.0,10.0,and 14.0at.%),the matrix proves to be eutectic.Thermal analysis results show that the initial martensitic transformation temperature(Ms)decreases from(412±5)K to(329±5)K as the Zn content increases from 1.5at.% to14.0at.%.The values of Msof Cu-Zr-Zn shape memory alloys are inversely proportional to the number and concentrations of valence electrons(i.e.,ev/a and cv),respectively,implying that the martensitic transformation in CuZrZn alloys could be of electronic nature.
  • Amorphization of Ni_(61)Nb_(39) Alloy by Laser Surface Treatment
  • The surface of Ni61Nb39 crystalline ingot was treated by laser surface melting with different processing parameters.A fully amorphous layer with a thickness of approximately 10μm could be produced on the top surface under optimal parameters.An amorphous-crystalline composite layer with the depth from 10 to 50μm,consisting of amorphous matrix and intermetallic phases of Ni3 Nb and Ni6Nb7,could be formed.The micro-hardness(about 831HV)of the treated surface was remarkably improved by nearly 100% compared with the value of the crystalline substrate caused by the formation of the fully amorphous structure.A finite volume simulation was adopted to evaluate the temperature distribution in the laser-affected zone of Ni61Nb39 alloys and to reveal the mechanism of glass formation in the laser-affected zone.
  • Serration Behavior in Zr-Cu-Al Glass-forming Systems
  • The metallic glass matrix composites(MGMCs)and bulk metallic glasses(BMGs)were studied by statistical analysis during plastic deformation at the strain rates of 2×10-2,2×10-3,and 2×10-4 s-1,respectively.No serration events occur in both MGMCs and BMGs during compression tests at the strain rate of 2×10-2 s-1.When deformed at the strain rate of 2×10-3 s-1,the BMG displays a larger plasticity,which is due to the larger serration events followed by a series of small serrations caused by the continuous movement of free volume.The amplitudes and elastic-energy densities increase with increasing the strain rates owing to many serrations in MGMCs.It is deduced that the Young′s modulus decreases from the normalized stress drop and fluctuations are observed on stressstrain curves,which is attributed to a lower coefficient according to the stick-slip model.
  • Interactions of Shear Bands in a Ductile Metallic Glass
  • Shear bands play a key role in the plastic deformation of metallic glasses(MGs).Even though there are extensive studies on the initiation and propagation of shear bands,the interactions among them have not been systematically studied yet.The interactions between the primary shear bands(PSBs)and secondary shear bands(SSBs)in a ductile Zr-based MG were studied.The residual stress near PSBs can deflect the propagation direction and reduce the propagation velocity of SSBs,which contributes to the plasticity and toughness of the MG.It was demonstrated that the probability and strength of the interactions between PSBs and SSBs would become stronger for MGs with larger Young′s modulus and smaller shear modulus,i.e.,larger Poisson′s ratio.These results are valuable in understanding the plastic deformation of MGs and may be helpful in designing new MGs with desirable mechanical properties.
  • Critical Shear Offset of Fracture in a Zr-based Metallic Glass
  • The nanoscale shear band operation process of Zr55Pd10Cu20Ni5Al10 metallic glass(MG)was reined in by constant force during well-designed loading-holding-unloading cyclic microcompression test.Through the test,it is revealed that the whole shear banding process involves three stages:shear band initiation,shear sliding and shear band arrest.Based on the energy balance principle,the size-affected speed of shear sliding is interpreted.The energy originated from the shear sliding leads to heat-up of the shear plane;therefore,the temperature in shear band increases with the size of shear offset caused by the energy accumulation during shear sliding.Taking the glass transition temperature as the critical temperature of fracture for the Zr-based MG,the critical shear offset is predicted to be approximately 190μm,fully in line with the experimental observation.This directly proved that the fracture of the MG is caused by the temperature rise during shear sliding.
  • Tribological Properties of a Dendrite-reinforced Ti-based Metallic Glass Matrix Composite under Different Conditions
  • The tribological properties of the in-situ dendrite-reinforced metallic glass matrix composite(Ti42Zr22V14-Cu5Be17)prepared by copper mould casting were analyzed at different normal loads under the dry condition and rainwater.The results showed that the average value of the frictional coefficients and micro-hardness ascended with increasing the normal load,while the wear rate showed a trend of decline under the dry condition.The electrochemical test results showed that the surface of samples was pitting corroded in the rainwater.The matrices were corroded first.Then the dendrites were exposed,leading to the damage of the surface.Both the frictional coefficients and wear rate of the composite in the rainwater were larger than those under the dry condition,primarily owing to the corrosion of chloride ions on the worn surface.The wear mechanisms of composites were mainly adhesive wear,accompanied by the abrasive wear under the dry condition and corrosive wear in the rainwater.The composites have higher wear resistance both under the dry condition and rainwater due to the lower wear rate.
  • Constitutive Models for Compressive Deformation of AZ80Magnesium Alloy under Multiple Loading Directions and Strain Rates
  • Two constitutive models,the modified Johnson-Cook model and the logarithm linear relation model based on empirical approach and data analysis,were presented to illustrate compressive deformation of magnesium alloys AZ80 under multiple loading directions and strain rates.The results of stress-strain curve analysis and sensitivity index analysis suggested that the stress held large fluctuations in loading direction of 90°.Model testing signified that the logarithm linear relation model was more proper than the modified Johnson-Cook model in view of relative mean square error and correlation coefficients.Moreover,numerical simulation building on established models also indicated that the logarithm linear model is more precise than the modified Johnson-Cook model.
  • Crystallization of a Ti-based Bulk Metallic Glass Induced by Electropulsing Treatment
  • The effect of electropulsing treatment(EPT)on the microstructure of a Ti-based bulk metallic glass(BMG)has been studied.The maximum current density applied during EPT can exert a crucial role on tuning the microstructure of the BMG.When the maximum current density is no more than 2 720A/mm~2,the samples retains amorphous nature,whereas,beyond that,crystalline phases precipitate from the glassy matrix.During EPT,the maximum temperature within the samples EPTed at the maximum current densities larger than 2 720A/mm~2 is higher than the crystallization temperature of the BMG,leading to the crystallization event.
  • Twinning Behavior of a Basal Textured Commercially Pure Titanium Alloy TA2 at Ambient and Cryogenic Temperatures
  • Twinning greatly affects the microstructure and mechanical performance of titanium alloys.The twinning behavior of a basal textured commercially pure titanium TA2 plates rolled to 4% reduction at the ambient and cryogenic temperatures has been investigated.Microstructures of the rolled samples were investigated by optical microscope(OM)and the twinning analysis was carried out based on orientation data collected by electron back-scatter diffraction(EBSD).{1122}contraction twins,{1124}contraction twins and {1012}extension twins have been observed.Twinning mode activity varied with rolling temperature.Twinning is considered as the dominant deformation mechanism during rolling at both temperatures for the strain condition.Larger proportion of grains activates twinning during cryorolling,and greater number and more diverse types of twins are observed;manifestly related to the suppression of dislocation slips at the cryogenic temperature.{1122}contraction twins are the dominate twin type within samples rolled at both temperatures.Several{1124}contraction twins are observed in the cryorolled sample while there are only a few in the sample rolled at room temperature.A few tiny{1012}twins have been identified in both samples.{1124}contraction twins are preferentially activated at cryogenic deformation temperature and the{1012}extension twins may result in local strain accommodation.
  • Effect of Oxygen on Microstructure Evolution and Glass Formation of Zr-based Metallic Glasses
  • The effect of oxygen on the microstructure evolution and glass formation of Zr-based bulk metallic glasses(BMGs)was studied in detail.It was found that oxygen did not form oxides or dissolve in glass matrix,but induced the precipitation ofα-Zr which has the high affinity and solubility of oxygen in the Zr-based bulk metallic glass(ZrBMG).With the precipitation ofα-Zr,the remaining melts contain much lower oxygen content and have strong glass formation,resulting in the formation ofα-Zr/BMG composite.The findings provide an important insight into the mechanism of the oxygen on glass formation,and give us a useful guideline to avoid the oxygen detrimental for designing new BMGs.
  • Serration and Noise Behavior in Advanced Materials(Yong ZHANG;Wei-hua WANG;Peter K.LIAW;Gang WANG;Jun-wei QIAO[5,6])
    A Brief Review of High Entropy Alloys and Serration Behavior and Flow Units(Yong ZHANG;Jun-wei QIAO;Peter K.LIAW)
    Self-organized Criticality Behavior in Bulk Metallic Glasses(Jun-wei QIAO;Zhong WANG)
    Microstructure Evolution and Mechanical Properties of Spray-deposited Al-21.47Si-4.73Fe-2.5Cu-0.9Mg Alloy(Yan-dong JIA[1,2];Fu-yang CAO;Pan MA;Jing-shun LIU;Jian-fei SUN;Gang WANG)
    Insight on Viscoelasticiy of Ti_(16.7)Zr_(16.7)Hf_(16.7)Cu_(16.7)Ni_(16.7)Be_(16.7)High Entropy Bulk Metallic Glass(Ji-chao QIAO;Jean-marc PELLETIER;Ning LI;Yao YAO)
    Rate Dependence of Serrated Flow and Its Effect on Shear Stability of Bulk Metallic Glasses(Bao-an SUN;Chain-tsuan LIU;Yong YANG)
    Influence of Zn Addition on Microstructures and Martensitic Transformation in CuZr-based Alloys(Kai-kai SONG;Dian-yu WU[1,2];Feng WAN;Xiao-jun BAI;Chong-de CAO)
    Amorphization of Ni_(61)Nb_(39) Alloy by Laser Surface Treatment(Zhong-xiang LU;Ran LI;Yan LI;Tao ZHANG)
    Serration Behavior in Zr-Cu-Al Glass-forming Systems(Zhong WANG;Jiao-jiao LI;Li-wei REN;Yong ZHANG;Jun-wei QIAO;Bao-cheng WANG)
    Interactions of Shear Bands in a Ductile Metallic Glass(Li-shan HUO[1,2];Jun-qiang WANG[1,2];Jun-tao HUO[1,2];Yuan-yun ZHAO[1,2];He MEN[1,2];Chun-tao CHANG[1,2];Xin-min WANG[1,2];Run-wei LI[1,2])
    Critical Shear Offset of Fracture in a Zr-based Metallic Glass(Zhi-yuan LIU;Yong YANG;Chain-tsuan LIU)
    Tribological Properties of a Dendrite-reinforced Ti-based Metallic Glass Matrix Composite under Different Conditions(Teng ZHANG;Xiao-min LIN;Hui-jun YANG;Yong LIU;Yong-sheng WANG;Jun-wei QIAO)
    Constitutive Models for Compressive Deformation of AZ80Magnesium Alloy under Multiple Loading Directions and Strain Rates(Xu-qing CHANG;Li-ying ZHANG;Yong-biao YANG;Jing-li REN)
    Crystallization of a Ti-based Bulk Metallic Glass Induced by Electropulsing Treatment(Yong-jiang HUANG[1,2];Xiang CHENG;Hong-bo FAN;Shi-song GUAN;Zhi-liang NING;Jian-fei SUN)
    Twinning Behavior of a Basal Textured Commercially Pure Titanium Alloy TA2 at Ambient and Cryogenic Temperatures(Jin-ru LUO;Xiao SONG;Lin-zhong ZHUANG;Ji-shan ZHANG)
    Effect of Oxygen on Microstructure Evolution and Glass Formation of Zr-based Metallic Glasses(Jia-lin CHENG[1,2,3];Guang CHEN;Qiang-qiang ZENG[1,2];Lu YUN[1,2];Feng XU)
    《钢铁研究学报:英文版》封面

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