• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Temperature effect on nanotwinned Ni under nanoindentation using molecular dynamic simulation

    2024-01-25 07:15:20XiHe何茜ZiyiXu徐子翼andYushanNi倪玉山
    Chinese Physics B 2024年1期
    關(guān)鍵詞:玉山

    Xi He(何茜), Ziyi Xu(徐子翼), and Yushan Ni(倪玉山)

    Department of Aeronautics and Astronautics,Fudan University,Shanghai 200433,China

    Keywords: nanoindentation,twin boundary,plastic deformation,molecular dynamics simulation

    1.Introduction

    Nanocrystalline metals exhibit elevated strength with reduced plasticity.The dislocation interactions are the main plastic mechanism.[1,2]Nanotwinned metals with introduced twin boundary defects perform ultrahigh strength and extraordinary ductility,[3–5]which attracts great attention.The introduced twin boundaries exhibit the block of dislocation slip and act as dislocation nucleation sites during plastic deformation.Luet al.proposed that the nanotwinned Cu achieves higher yield strength when the twin boundary spacing decreases,while a softening behavior appears when the twin boundary spacing is less than 15 nm.[6]Furthermore,Mousaviet al.discovered that there exists a softening temperature,below which the nanotwinned Cu hardens continuously as the twin spacing is reduced.[7]It is shown that mechanical behaviors and plastic deformation of nanotwinned metals are strongly influenced by temperature.

    Recently, the temperature effect on the twin boundary was investigated.Zhaoet al.reported that the nanotwinned Ti at a low temperature of 77 K can display elevated strength and enhanced ductility.[8]Larranagaet al.explored the hightemperature plasticity at the twin boundary in Al through straining experiments.[9]Shabibet al.credited that the twin migration process becomes faster and dislocation storage capacity is reduced at higher temperatures in the tensile experiment of 2D-columnar nanotwinned Cu films.[10]Huanget al.simulated the uniaxial tensile loading at different temperatures of nanotwinned Mg and found that temperature has a significant effect on the dislocation slip mechanism in the plastic deformation stage.[11]The shear loading simulation on nanotwinned Cu revealed that the deformation mechanism changes from the twin migration to deformation twinning with increasing temperature.[12]The above-mentioned studies of temperature effect of nanotwinned metals on microstructure deformation focus on uniform tension,compression,and shear load.

    The localized indentation loading of nanoindentation is a method to investigate the mechanical responses and deformation mechanisms of films through experiments and simulations.The nanoindentation simulation is often used to investigate the atomic deformation of FCC nanotwinned materials including twinning, detwinning, and twin migration under room temperature.[13–16]The nanoindentation experiments about the temperature effect on FCC nanotwinned materials focus on mechanical behaviors of hardness,[17–19]and strain rate sensitivity.[2]Yanget al.revealed a large temperaturedependent increase in strain rate sensitivity and decrease in hardness through the nanoindentation experiment on nanotwinned Cu.[2]Yanget al.found that the strain rate of nanotwinned Cu is a function of temperature and hardness through multi-temperature indentation creep experiments.[17]

    However, the twin boundary strengthening and the microstructure evolution of nanotwinned Ni with the increasing temperature under nanoindentation have not yet been explored via molecular dynamic simulation.Nickel (Ni) is one of the most technologically important high-temperature FCC metals,which has high temperature stability, high strength, and wear resistance.This paper investigates the atomic deformation of nanotwinned Ni (nt-Ni) to explain the mechanical properties in comparison with nanocrystalline Ni (nc-Ni) at five temperatures (10 K, 300 K, 600 K, 900 K, and 1200 K) under nanoindentation.The mechanical properties of critical loads,hardness, and indentation size effect of nt-Ni are analyzed through atomic deformation of incipient plasticity and dislocation transmission in comparison with nc-Ni.In addition,the evolution of atom types and dislocation density of nt-Ni are further studied to quantify atomic structure changes at various temperatures in comparison with nc-Ni.This study reveals the evolution of deformation mechanisms of high-strength nt-Ni at different temperatures, providing a theoretical basis for manufacturing and use of nt-Ni.

    2.Simulation models and methods

    In order to better investigate atomic structures of nc-Ni and nt-Ni under nanoindentation at different temperatures,the nc-Ni and nt-Ni films are established in a three-dimensional Cartesian coordinate system,as shown in Figs.1(a)and 1(b).The size of the model is 18.92 nm×20.69 nm×9.75 nm,which is large enough to eliminate boundary effects for the indentation depth in our simulation.The size is coincident with the as-deposited nanotwinned Ni specimen for an average grain size value of 28 nm.[20]There are 357504 Ni atoms contained in the nc-Ni and nt-Ni models, which is enough to analyze the atomic deformation of nc-Ni and nt-Ni at different temperatures during the indentation process.To avoid potential boundary effects as a result of the small simulation dimensions of nc-Ni and nt-Ni,periodic boundary conditions are applied along thexandydirections so that the simulation box is replicated throughout the space to form an infinity lattice.The boundary condition of thezdirection is set as free boundary conditions to realize the indentation process along thezdirection.The nc-Ni in Fig.1(a) has the lattice orientations along thex,yandzaxes in[1ˉ10],[11ˉ2]and[111]directions.For the nt-Ni[Fig.1(b)],two twin boundaries are introduced into the film by setting different lattice orientations.The lattice orientations of the 1st and 3rd layers in thex,yandzaxes are along[1ˉ10],[11ˉ2]and[111].The lattice orientations of the 2nd layer along thex,yandzaxes are[ˉ110],[ˉ1ˉ12]and[111].Thus,the lattice orientations of the two regions next to the twin boundary are opposite and mirror symmetric.Two boundaries are placed at 3.14 nm and 6.29 nm below the surface individually.The twin spacing around 3 nm is frequently attributed in as-deposited nanotwinned Ni samples,which is enough for observing atomic structures.[4]All atoms of the nc-Ni and nt-Ni films whosezcoordinates are less than 0.78 nm are fixed to prevent the rigid movement of the whole films along thezaxis during the nanoindentation process.

    Table 1.The elasticity constants of Ni determined by Adam et al.,and EAM potential compared with the experimental data.[21,22]

    The nanoindentation simulations are performed by using the large-scale parallel molecular dynamics package LAMMP[24]to examine the multiple mechanisms.A repulsive potential field is used to describe the force on each atom in contact with the indenter.[25,26]In this study,the embedded atom potential (EAM) method of Ni developed by Adamset al.is used to describe the interaction between Ni atoms.[23]

    The elasticity constants are very close to the experimental data (see Table 1), which provide good results in modeling crystal defects.The repulsive potential has been extensively validated in various loading conditions, including tensile[27,28]and shear.[29]In recent years, especially in indentation simulation,[30–32]researchers have achieved good results in capturing stress responses, atomic deformations of Ni across different temperature ranges:[33–37]

    wherekis the contact stiffness, which is set to 10 eV·?A?3,ris the distance between the atom and the center of the indenter, andRis the radius of the indenter.The lattice constant of single Ni (aNi) is 0.3520 nm.The spherical rigid indenter with radiation of 4 nm is used.The simulations are performed under five temperatures, namely 10 K,300 K,600 K,900 K,and 1200 K.The time step is set to 1 fs.In each simulation,firstly the velocity of the movable atom is initialized and set randomly at the corresponding temperature.Then the whole film is subjected to 100000 steps of temperature relaxation in the isothermal-isobaric(NPT)ensemble to reach the set temperature, in which the total number of atoms, pressure, and temperature of the film remain unchanged.Then, the indentation is carried out alongz-axis with a constant velocity of 10 m/s under the canonical(NVT)ensemble,in which the total number of atoms, the volume, and the temperature of the film remain unchanged.The visualization is performed by using OVITO.[38,39]

    3.Results

    3.1.Temperature effect on critical load

    To learn the temperature influence on critical load during nanoindentation,we present the load responses(P–h)of nc-Ni and nt-Ni at the temperatures 10 K,300 K,600 K,900 K,and 1200 K,as shown in Figs.2(a)and 2(b).The simulation results of nc-Ni demonstrate the similar trend as the load response of nc-Ni indentation experiment.[40–43]The yield points of nc-Ni and nt-Ni in theP–hresponses are labeled as A, B, C,D, E [Fig.2(a)] and A', B', C', D', E'[Fig.2(b)], with the corresponding indenter depth and critical load,respectively,at 10 K,300 K,600 K,900 K,and 1200 K.The yield points correspond to the onset of plasticity where dislocations nucleate from the indenter,[3]which is the critical point for the elasticplastic transition beneath the indenter.Both the yield indenter depths and critical loads of nc-Ni and nt-Ni decrease with the increasing temperature,in agreement with past nanoindentation simulation results on nanocrystalline materials.[44]Although both the nt-Ni and nc-Ni yield at the similar indenter depth,the nt-Ni shows an elevated critical load compared with nc-Ni due to the existence of the twin boundary.The critical load difference between the nc-Ni and nt-Ni is presented in Fig.3.Compared to nc-Ni, nt-Ni still has strengthening effect at high temperatures,especially at 300 K–900 K.Detailed atomic structures are presented in the next section.

    Fig.2.Load-indenter depth responses at 10 K, 300 K, 600 K, 900 K,and 1200 K during nanoindentation of(a)nc-Ni and(b)nt-Ni.

    Fig.3.Critical loads at 10 K, 300 K, 600 K, 900 K, and 1200 K of nc-Ni and nt-Ni.

    3.2.Temperature effect on critical hardness

    The hardness is a measure of a material’s resistance to permanent deformation under an applied load.[45]In nanoindentation simulation,contact hardnessHis defined as

    wherePis the indenter force andAcis the projected area of the contact surface between the indenter and the film along the directionz[111](called the contact area).The projected area is calculated by[46]

    Here,xmaxandxminare the maximum and minimum ofxcoordinates of atoms in contact with the indenter,ymaxandyminare the maximum and minimum ofycoordinates of atoms in contact with the indenter.

    Fig.4.Schematic diagram of the contact between the indenter and the film surface and surface atoms.

    The hardness is generally considered to be correlated with contact depthhc.[42]For the spherical indenters, at the same moment of indentation, the schematic diagram ofhcandhis shown in Fig.4.The contact depthhcis defined as

    The hardness–contact depth responses of nc-Ni and nt-Ni at various temperatures are shown in Figs.5(a) and 5(b).The simulated results of nc-Ni demonstrate the trend similar to the hardness response of nc-Ni indentation experiment.[40–43]The results also align well with some nc-Ni indentation simulations.[47,48]The yield points of nc-Ni and nt-Ni in theH–hcresponses are labeled as A, B, C, D, E [Fig.5(a)] and A', B', C', D', E'[Fig.5(b)], with the corresponding contact depth and critical hardness respectively at 10 K, 300 K,600 K,900 K,and 1200 K.Compared with theP–hcurves,the hardness–contact depth response (H–hc) offers insights into localized mechanical properties and exhibits trends that correspond to the material’s microstructure, phase changes, and deformation mechanisms at different contact depths.The values of critical hardness of nc-Ni and nt-Ni decrease with the increasing temperature.Compared to nc-Ni, the nt-Ni shows a strengthening at all temperatures, as shown in Fig.6.The tensile experiment response of yield strength with temperature on nt-Ti reported by by Zhaoet al.also has the same decreasing variation tendency as our nanoindentation results.[8]The above result is in accordance with the decreasing critical load responses with temperature,which indicates that nt-Ni still has strengthening effect at high temperature,especially at 300 K–900 K.

    Fig.5.Hardness–contact depth responses of(a)nc-Ni and(b)nt-Ni at 10 K,300 K,600 K,900 K,and 1200 K during nanoindentation.

    Fig.6.The hardness difference between nc-Ni and nt-Ni.

    3.3.Temperature effect on dislocation nucleation

    Detailed atomic structure evolution could provide information about the underlying mechanisms of incipient plasticity corresponding to the yield event.The increased critical load and hardness are closely related to the atomic structures of nt-Ni.

    Fig.7.(a)Thompson’s tetrahedron illustrating the slips between the indenter surface and coherent twin boundary(CTB)in nt-Ni.(b)Thompson tetrahedron notation for FCC slip systems.

    At the yield event, the dislocations are nucleated and emitted from the indented surface, followed by stacking faults, which correspond to the transition from elasticity to plasticity.[3]Figure 7 shows Thompson’s tetrahedron illustrating the FCC slips.The dislocation types and slip planes at the yield point of nc-Ni and nt-Ni are presented in Fig.8.

    Fig.8.The snapshots of the dislocation type and slips at the yield point of (a1)–(a5) nc-Ni and (b1)–(b5) nt-Ni at 10 K, 300 K, 600 K, 900 K,and 1200 K.The DCA, DCB, and DBA are the slip planes (refer to Thompson’s tetrahedron in Fig.7).

    For nc-Ni at five temperatures [Figs.8(a1)–8(a5)], only Shockley dislocations are generated at the yield point.The slip planes of (1ˉ11) and (ˉ111) are activated.For nt-Ni, at 10 K[Figs.8(b1)],perfect and Shockley dislocations are found in (11ˉ1) slip plane.At 300 K [Fig.8(b2)], perfect, stair-rod and Shockley dislocations are observed in(1ˉ11)and(ˉ111)slip planes.The Shockley dislocations are found at the temperature of 600 K in(1ˉ11)slip planes[Fig.8(b3)],900 K[Fig.8(b4)]in(11ˉ1)slip plane,and 1200 K in(1ˉ11)slip plane[Fig.8(b5)].Compared to nc-Ni,more active dislocations of perfect,stairrod and Shockley dislocations nucleate and all slip planes of(1ˉ11), (ˉ111) and (11ˉ1) are activated.The increased dislocation types and slip systems of nt-Ni are closely related to the elevated stacking fault energy.The result indicates that active dislocation nucleation occurs and multiple slips are activated due to the impediment of the twin boundary in nt-Ni, which illustrates the strengthening of nt-Ni at different temperatures.

    4.Discussion

    4.1.Temperature effect on the indentation size effect of nt-Ni and nc-Ni

    The characteristic of nanoindentation with an indenter is that the contact hardness decreases with contact depth.The well-established Nix–Gao model[18]is used to analyze the indentation size effect by the hardness responses, in which the hardness decreases with the increasing contact depthhcafter the yield points(onset of plasticity)in nc-Ni and nt-Ni.Based on geometrically necessary dislocations,this model can obtain the following relationship:

    whereHis the hardness of the material under current indentation contact depth (hc).H0is the macroscopic sizeindependent hardness at whichHwill converge to as the indentation depth becomes large enough (also called “infinite hardness”).Here,h?is the characteristic indentation length scale depending on the microstructure of the material.[18]We fit the simulated hardness data with Eq.(5) using non-linear least squares,as shown in Figs.9(a)and 9(b).The decreasing hardness of nc-Ni and nt-Ni with contact depth after the yield point can be well described using the Nix–Gao model.Both the hardness behaviors of nc-Ni and nt-Ni show an indentation size effect.

    Fig.9.Hardness–contact depth responses of(a)nc-Ni and(b)nt-Ni at 10 K,300 K,600 K,900 K,and 1200 K during nanoindentation.

    As is well known,h?is the material length scale parameter, which is referred to the material-dependent plasticity length scale.According to Fleck and Hutchinson,[49]h?characterizes the spacing between dislocation obstacles (in the case of pure metal,h?represents the distance between other dislocations and their associated junctions and locks).In other words,h?can be understood as the mean-free path of dislocation and reflects the magnitude of the indentation size effect.[50]Theh?values of nc-Ni and nt-Ni at different temperatures are shown in Fig.10.Obviously,h?of nc-Ni is greater than nt-Ni, indicating that the hardness of nc-Ni shows more significant indentation size effect compared to nt-Ni.Notably,h?declines considerably in nc-Ni as the temperature rises, in agreement with nanoindentation results on nanocrystalline Cu.[50,51]Diversely,h?in nt-Ni first declines and then increases as the temperature rises.The smallerh?of nt-Ni indicates different dislocation nucleations and slips during plastic deformation in comparison with nc-Ni.It is desirable to explore the evolution of dislocation nucleation and propagation with the increasing temperature,which is studied in the following.

    Fig.10.Characteristic indentation length scale h?of nc-Ni and nt-Ni at 10 K,300 K,600 K,900 K,and 1200 K during nanoindentation.

    4.2.Temperature effect on atomic deformation of nc-Ni and nt-Ni

    It is known that the main plastic deformation mechanisms in FCC metals are dislocation cross-slip parallel or inclined to the surface,which will compete under different conditions.In this context,the twin boundary plays a crucial role in hindering the propagation of dislocations, as noted in the incipient plasticity analysis.The material length scale parameterh?is closed related to atomic deformation in the plastic stage.[52]To gain insight into the atomic deformation and the impediment effect of twin boundaries in nt-Ni under localized indentation loading at different temperatures,the dislocation transmission of nt-Ni is investigated in comparison with the corresponding atomic structures of nc-Ni,as shown in Fig.11.After the yield point,the dislocation transmission is an important deformation mechanism between dislocations and twin boundaries in the plastic stage, where partial dislocations first are emitted from the upper twin boundary.[46]From Fig.11,it can be found that in nc-Ni,the dominant deformation mechanism is dislocation slips and twinning, which are also observed in nanoindentation experiments of nc-Ni.[53,54]In nt-Ni,continuous emission of leading partial dislocations and trailing partial dislocations and steps along the twin boundaries are found, in align with observation in nanoindentation experiments of nt-Ni.[54]

    Fig.11.Atomic structures of(a1)–(a5)nc-Ni and(b1)–(b5)nt-Ni when the dislocation transmission occurs in nt-Ni at 10 K (indenter depth hnt?Ni =1.94 nm),300 K(indenter depth hnt?Ni =1.22 nm),600 K(indenter depth hnt?Ni=1.34 nm),900 K(indenter depth hnt?Ni=1.46 nm)and 1200 K (indenter depth hnt?Ni = 0.88 nm).The CLS refers to the confined layer slips.The yellow rectangular boxes refer to the slip planes(111)parallel to the surface or twin boundary.The color of atom represents the local lattice structure of the atom,where green for FCC,red for HCP,blue for BCC,and gray for“other”lattice structures.

    At 10 K, the atomic structures of nc-Ni and nt-Ni at the first dislocation transmission can be seen in Figs.11(a1) and 11(b1).The dislocation slips are restrained because of the high activation energy acquired and dislocation block occurs in both nc-Ni and nt-Ni.In nc-Ni [Fig.11(a1)], two-layer partial slips parallel to the indented surface with the extension of stacking fault and multiple confined layer slips under the indenter surface are formed.Partial slips parallel to grain boundaries are pronounced at extremely low temperatures in nanocrystalline metals under nanoindentation, compression and tensile experiment.[55–59]The difference is that the confined layer slips and partial slips parallel to the indenter surface are only formed under the indenter due to concentrated loading and dislocation block.In nt-Ni [Fig.11(b1)],compared to nc-Ni, the dislocation propagation and the extension of stacking faults are impeded due to the twin boundary.Strengthening structures of multiple confined layer slips[(ˉ111),(1ˉ11),(11ˉ1)]between the indenter and the upper twin boundary are formed.At the same time,the partial twin migration acts as softening structure and steps on the twin boundary are the dislocation nucleation sources.The partial slips parallel to the twin boundary dominate the atomic deformation of nt-Ni at 10 K,which will soften the nt-Ni but improve the plasticity.[13]Figure 12 further reveals that great partial slips parallel to the twin boundary (111) dominate before dislocation transmission occurs,which will greatly delay the dislocation transmission event.

    Fig.12.Partial slips parallel to twin boundary in nt-Ni at 10 K,h=1.22 nm.The CLS refers to the confined layer slips.The yellow rectangular boxes refer to the slip planes(111)parallel to the surface or twin boundary.

    At 300 K, the dislocation slip is enabled in nc-Ni[Fig.11(a2)], partial slips parallel to the indented surface are still formed, while the range is smaller than that at 10 K.In nt-Ni[Fig.11(b2)],the dislocation block faded and no partial slips parallel to the twin boundary are formed, which greatly brings forward the dislocation transmission and decreases the plasticity.The confined layer slips between the indenter surface and twin boundary are formed.The twin migration and great dislocation nucleation steps on the twin boundary contribute to the plasticity of nt-Ni in comparison to that of nc-Ni.

    Figure 11(a3)illustrates a smaller range of partial slip parallel to the indenter surface in nc-Ni at 600 K in comparison with that at 300 K.In nt-Ni [Fig.11(b3)], compared to 300 K, more confined layer slips and less twin migration are found,which form strengthening structures under nanoindentation.In addition,more steps are formed on the twin boundary, which indicates the formation of more dislocation nucleation sites on the twin boundary and contributes to the elevated plasticity.It can be inferred that elevated temperature promotes the interaction between dislocations,which is sufficiently flexible to allow the propagation of deformation along the slip planes.

    In nc-Ni at 900 K[Fig.11(a4)],the decreased partial slips parallel to the indenter surface and increasing confined layer slips are formed compared to 600 K.Compared to 600 K,the nt-Ni at 900 K[Fig.11(b4)]has fewer confined layer slips and steps on the twin boundary,but it has a larger twin migration.Moreover,in nt-Ni at 900 K,the dislocation interaction of dislocation pinning and dissociation should be noted.Continuous dislocation lines are separated into several small dislocation segments[Fig.13(a)], and then the separated dislocation segments are gathered to form dislocation pinning phenomena[Fig.13(b)].Dislocation dissociation and pining occur before the dislocation transmission at 900 K.On the one hand, the number of disordered atoms increases due to the enhancement of atomic thermal motion under high temperatures,which will hinder the motion of dislocations and separate the continuous dislocation line.On the other hand,the Shockley partial dislocations are emitted from the indented surface and interact with the stacking fault structure frequently due to the impediment of twin boundary and localized stress, resulting in dissociation and pinning of Shockley dislocations.This indicates that dislocation interaction occupies an important position and the strengthening effect of the twin boundary is decreased in the plastic deformation.

    Fig.13.(a)Dislocation dissociation(h=0.52 nm)and(b)dislocation pinning(h=0.54 nm)at 900 K.

    In nc-Ni at 1200 K[Fig.11(a5)],the range of partial slips parallel to the indenter surface is narrowed and less confined layer slips are formed compared to those at 900 K.In nt-Ni[Fig.11(b5)], fewer confined layer slips in comparison with those of nt-Ni at 900 K, and no twin migration is observed.At the dislocation transmission point of nt-Ni,the dislocation loop directly traverses the upper twin boundary at the indenter depth of 0.88 nm.The perfect dislocation dissociates into three Shockley partial dislocations, two moving downward and one propagating transversely on the upper twin boundary.The phenomenon indicates the fading effect of the twin boundary hindering dislocation propagation.The dislocation interactions are also observed at 1200 K.Dislocation dissociation[Fig.14(a)]and pining[Fig.14(b)]are found to happen more frequently at 1200 K than at 900 K.It can be inferred that high temperature promotes the transition between the dislocation pining and dissociation.The result indicates that the strengthening effect of twin boundaries is reduced and dislocation interactions become the main deformation mechanism in nt-Ni at 1200 K.

    Fig.14.(a)Dislocation dissociation(h=0.60 nm)and(b)dislocation pinning(h=0.58 nm)at 1200 K.

    From the above analysis,it is found that compared to the downward extended dislocation slips in nc-Ni,the twin boundary of nt-Ni limits the dislocation nucleation and propagation to form a large amount of confined layer slips between the indenter surface and twin boundary at various temperatures.As the temperature increases,the dominant deformation of partial slips parallel to the indenter surface in nc-Ni decreases,which corresponds to the decrease ofh?.The deformation mechanism of nt-Ni that changes with the increasing temperature is different from that of nc-Ni.For nt-Ni, the changes of confined layer slip with the increasing temperature are in accordance with the change ofh?, which first decreases and then increases.The partial slips parallel to the twin boundary dominate the plasticity first.With the increasing temperature, the confined layer slips first increase and then decrease, which is helpful for the deformation propagation along slip planes.The dislocation interaction of dislocation pinning and dissociation then dominates the plastic deformation.It should be noted that the nt-Ni has strengthening structures at 300 K–900 K with multiple confined layer slips,great steps on the twin boundary and narrowed twin migration.

    4.3.Quantitative analysis

    4.3.1.Dislocation density of nc-Ni and nt-Ni

    The dislocation density refers to the total length of dislocations contained in a unit volume crystal, or the number of dislocation lines crossing the unit cross-sectional area, which is closely related to dislocation motion.To complementally explain and analyze the dislocation motion at the dislocation transmission with temperature in nc-Ni and nt-Ni,the dislocation is calculated by the following formula:

    whereLis the total dislocation length,andVis the model volume.The continuous propagation of dislocations will lead to a pileup of dislocations,which will increase the strength of the material,and the dislocation densities of nc-Ni and nt-Ni vary at different temperatures,as shown in Fig.15.

    Fig.15.Dislocation density of nc-Ni and nt-Ni when the dislocation transmission occurs in nt-Ni at 10 K (indenter depth hnt?Ni =1.94 nm), 300 K(indenter depth h=1.22 nm), 600 K(indenter depth h=1.34 nm),900 K(indenter depth h=1.46 nm),and 1200 K(indenter depth h=0.88 nm).

    It is shown that the dislocation density of nc-Ni is greater than that of nt-Ni because the twin boundary will hinder the propagation of dislocation and great dislocations are absorbed by the twin boundary.At 10 K, the dislocation slip is suppressed due to low stacking fault energy and then causes the increase of dislocation density.It can be observed that both nc-Ni and nt-Ni have high dislocation density at 10 K.The high dislocation density contributes lots to the formation of partial slip parallel to the indenter surface in nc-Ni[Fig.11(a1)]and nt-Ni [Figs.11(b1) and 12].Dislocation density decreases in nc-Ni and nt-Ni at 300 K because of the decrease of dislocation block and activation of dislocation slips.Great atoms can obtain sufficient kinetic energy to break through the energy barrier to form inclined dislocation slips.It should be noted that the dislocation density of nt-Ni at 600 K is carried to a higher level and nearly identical to that of nc-Ni,which is consistent with the increased confined layer slip and steps on the upper twin boundary in the atomic structures in nt-Ni[Fig.11(b3)].The elevated dislocation density contributes much to the increased plasticity in nt-Ni at 600 K.The dislocation density declines sharply because the dislocation pinning and dissociation are activated at 900 K[Figs.13(a)and 13(b)]and 1200 K[Figs.14(a)and 14(b)].At 900 K and 1200 K,the difference in dislocation density between nc-Ni and nt-Ni decreases and becomes uniform,which indicates that the twin boundary gradually loses strengthening efficacy and the dislocation dominates plasticity of nt-Ni.

    4.3.2.Atomic structures types of nc-Ni and nt-Ni

    Atomic structure type change contributes a lot to the change of plastic structure such as confined layer slip, twinning,and twin migration under localized indentation loading.In order to further understand the plastic structure changes,the FCC atoms, disordered atoms and HCP atoms at the dislocation transmission points at five temperatures are calculated.The other atoms represent disordered atoms, and the number of other atoms indicates the intensity of the thermal motion of atoms.Greater disordered atoms indicate more violent atom thermal motion and cause softening.HCP atoms’attribution is closely related to the strengthening structures of nanotwinned materials under localized indentation loading.HCP atoms construct twin boundaries, twin migration, confined layer slips,and stacking faults in the nanotwinned materials under localized indentation loading.HCP atoms on twin boundaries, confined layer slips and stacking faults enhance nanotwinned materials, while HCP atoms on twin migration will lead to softening of the material.

    The FCC atoms and disordered atom numbers of nc-Ni and nt-Ni with the temperature at the first dislocation transmission are presented in Figs.16(a)and 16(b),respectively.It can be found that with the increasing temperature, the FCC atoms of both nc-Ni and nt-Ni decrease (Fig.16(a)), while the disordered atoms increase with the increasing temperature(Fig.16(b)).Moreover,fewer FCC atoms and more disordered atoms are found in nt-Ni compared with nc-Ni.The results reveal more active atoms motion and transformation happened in nt-Ni compared with nc-Ni due to the hindrance of the twin boundary.The attribution of HCP atoms in nc-Ni and nt-Ni is shown in Fig.17 when the dislocation transmission occurs.In nt-Ni, the HCP atoms exist and construct the structures of confined layer slips and partial slips parallel to the indenter surface.The HCP atoms in nt-Ni are much greater than that in nc-Ni due to the existence of twin boundary.The HCP atoms in nc-Ni and nt-Ni decrease with the increasing temperature.This reveals that increasing temperature leads to changes in atomic structure of the twin boundary and stacking fault.Detailed HCP atoms attribution in nt-Ni is studied.

    Fig.16.(a)FCC atoms and(b)disordered atom(“other atoms”in ovito)number of nc-Ni and nt-Ni at 10 K,300 K,600 K,900 K,and 1200 K when the dislocation transmission occurs in nt-Ni at 10 K (indenter depth hnt?Ni =1.94 nm), 300 K (indenter depth h=1.22 nm),600 K(indenter depth h=1.34 nm),900 K(indenter depth h=1.46 nm),and 1200 K(indenter depth h=0.88 nm).

    Fig.17.HCP atom number and attribution of nc-Ni and nt-Ni at 10 K,300 K,600 K,900 K,and 1200 K at the dislocation transmission when the dislocation transmission occurs in nt-Ni at 10 K (indenter depth hnt?Ni =1.94 nm), 300 K (indenter depth h=1.22 nm), 600 K (indenter depth h=1.34 nm), 900 K (indenter depth h=1.46 nm), and 1200 K(indenter depth h=0.88 nm).

    At 10 K, the stacking fault atoms (4652, 24.5%) are the largest among all temperatures,which corresponds to the partial slips parallel to the twin boundary and confined layer slips[Figs.11(b1) and 12].At 300 K, the stacking fault atoms among HCP atoms occupy 13.9% (2527), smaller than that of nt-Ni at 10 K.However, the atoms participating in twin migration is 10.5% (1901) [Fig.11(b2)], larger than nt-Ni at 10 K.The change of HCP atoms indicates the softening of 300 K, compared to that at 10 K.At 600 K, 16.1% (2734)stacking fault HCP atoms are found,which is larger than that at 300 K.There is 7.4% (1251) of twin migration atoms that are recorded, which is smaller than that at 300 K.The HCP attribution is in good agreement with the atomic structures of nt-Ni at 600 K [Fig.11(b3)].The HCP attribution can effectively mitigate the softening caused by increasing temperature.Compared to 600 K,the stacking fault HCP atoms of nt-Ni at 900 K decrease(2438,14.6%)but twin migration HCP atoms increase (1469, 8.8%), so causing the reduction of confined layer slip in Fig.11(b4).At 1200 K,the stacking fault atoms of nt-Ni have a substantial reduction(587,4.5%)without no twin migration,as shown in Fig.11(b5).The quantitative analyses of dislocation density and atomic structure on the one hand elaborate that the strengthening of nt-Ni at different temperatures is attributed to twin boundaries and confined layer slips,and on the other hand further illustrate that the atomic deformation of nt-Ni is changed with the increasing temperature during dislocation transmission.

    5.Conclusion

    In this paper, the atomic deformation of nt-Ni with twin boundaries at different temperatures under nanoindentation is investigated in comparison with nc-Ni.The results are as follows.

    (i)Elevated critical load and hardness are found in nt-Ni compared to nc-Ni at the onset of plasticity due to the hindrance of twin boundary,where perfect,stair-rod,and Shockley dislocations are activated at (1ˉ11), (ˉ111), and (11ˉ1) slip systems in nt-Ni compared to only Shockley dislocation nucleation at(1ˉ11)and(ˉ111)slip planes of nc-Ni.

    (ii)Less significant indentation size effect is found in nt-Ni compared with nc-Ni in the plastic stage since twin boundaries hinder dislocation nucleation and propagation.The atomic deformation associated with the indentation size effect changes with the increasing temperature.Different from the decreasing dislocation slips in nc-Ni, the atomic deformation of nt-Ni changes as temperature rises: from the great partial slips and expansion parallel to the twin boundary dominate the plasticity (~10 K), to the great confined layer slips and decrease twin migration contribute to the (300 K–600 K), to the decrease of confined layer slips with the dislocation interaction of dissociation and pinning(900 K–1200 K).

    (iii)Dislocation density and atom types through quantitative analysis further reveal the dislocation motion of dislocation slip and dislocation block and explain the atomic structure change of confined layer slip, stacking fault and twin migration.The strengthening structures of nt-Ni are attributed to twin boundaries and confined layer slips,which change as the temperature rises.

    Acknowledgment

    This work was supported by the National Natural Science Foundation of China(Grant No.11572090).

    猜你喜歡
    玉山
    水仙盆景欣賞
    花卉(2024年5期)2024-03-23 08:08:24
    水仙盆景欣賞
    花卉(2024年3期)2024-02-26 05:11:52
    月季盆景欣賞(二)
    花卉(2023年15期)2023-08-09 08:05:04
    月季盆景欣賞(一)
    花卉(2023年13期)2023-07-07 10:26:24
    黃楊盆景欣賞(一)
    花卉(2023年11期)2023-06-09 08:13:30
    新年獻(xiàn)辭
    附式石盆景欣賞
    花卉(2021年9期)2021-05-15 09:57:28
    Glassy dynamics of model colloidal polymers:Effect of controlled chain stiffness?
    懸崖式盆景欣賞(一)
    花卉(2020年5期)2020-03-16 08:13:48
    論玉山雅集與元后期文士群體的追求
    久久久精品国产亚洲av高清涩受| www.熟女人妻精品国产| 搡老乐熟女国产| 91老司机精品| 亚洲三区欧美一区| 人妻一区二区av| 女同久久另类99精品国产91| 国产亚洲精品第一综合不卡| 国产伦理片在线播放av一区| 中国美女看黄片| 久久久久久亚洲精品国产蜜桃av| 真人做人爱边吃奶动态| 最新的欧美精品一区二区| 精品国产乱码久久久久久小说| 国产成人av教育| 久久精品91无色码中文字幕| 国产精品成人在线| 操美女的视频在线观看| 丰满迷人的少妇在线观看| 亚洲成人手机| 精品福利永久在线观看| 最黄视频免费看| 高清黄色对白视频在线免费看| 精品视频人人做人人爽| 十八禁网站网址无遮挡| 国产亚洲欧美在线一区二区| 一级,二级,三级黄色视频| 夜夜爽天天搞| 女人久久www免费人成看片| 人妻 亚洲 视频| 国产91精品成人一区二区三区 | 国产精品av久久久久免费| 免费看十八禁软件| 亚洲成a人片在线一区二区| 一级片'在线观看视频| 欧美人与性动交α欧美精品济南到| 国产成人欧美在线观看 | 啦啦啦免费观看视频1| 亚洲第一青青草原| 69av精品久久久久久 | 最近最新中文字幕大全电影3 | 久久毛片免费看一区二区三区| 少妇粗大呻吟视频| 亚洲精品美女久久久久99蜜臀| 久久久久久久久久久久大奶| 久久午夜综合久久蜜桃| 免费在线观看日本一区| 老熟妇仑乱视频hdxx| 另类亚洲欧美激情| 亚洲av欧美aⅴ国产| 极品人妻少妇av视频| 9色porny在线观看| 久久久久网色| 男人舔女人的私密视频| 精品一区二区三卡| 大香蕉久久网| 欧美人与性动交α欧美精品济南到| 精品少妇久久久久久888优播| 热re99久久精品国产66热6| 一本一本久久a久久精品综合妖精| 视频在线观看一区二区三区| 国产成人av激情在线播放| 动漫黄色视频在线观看| 久久久国产精品麻豆| 亚洲人成电影免费在线| 久久久久久久久免费视频了| 欧美日韩黄片免| 91麻豆精品激情在线观看国产 | 精品人妻在线不人妻| 交换朋友夫妻互换小说| 久久午夜综合久久蜜桃| 成人av一区二区三区在线看| 国产av一区二区精品久久| 久久久久久久久久久久大奶| 日本av手机在线免费观看| 精品国产亚洲在线| 国产欧美日韩精品亚洲av| 男人操女人黄网站| 精品国内亚洲2022精品成人 | 精品亚洲成国产av| 国产有黄有色有爽视频| svipshipincom国产片| 久久国产精品影院| 日本黄色日本黄色录像| 欧美黄色淫秽网站| av免费在线观看网站| 国产精品香港三级国产av潘金莲| 久久免费观看电影| 脱女人内裤的视频| 999久久久国产精品视频| 国产精品一区二区在线观看99| 亚洲人成电影观看| 久久久久久久久免费视频了| 精品一区二区三区av网在线观看 | 色综合欧美亚洲国产小说| 亚洲成人手机| 国产在线一区二区三区精| h视频一区二区三区| 国产在线免费精品| 日本黄色视频三级网站网址 | 成人国语在线视频| 亚洲精品av麻豆狂野| 国产精品1区2区在线观看. | 精品国产乱子伦一区二区三区| 夫妻午夜视频| 久热爱精品视频在线9| 国产亚洲精品第一综合不卡| 天堂中文最新版在线下载| 欧美日韩一级在线毛片| 日日摸夜夜添夜夜添小说| 丰满饥渴人妻一区二区三| 考比视频在线观看| 国产成人精品久久二区二区91| 热99re8久久精品国产| 狂野欧美激情性xxxx| 国产精品熟女久久久久浪| 精品视频人人做人人爽| 波多野结衣一区麻豆| 日日夜夜操网爽| 亚洲自偷自拍图片 自拍| 亚洲精品国产色婷婷电影| 中文字幕最新亚洲高清| 亚洲精品成人av观看孕妇| 黄色毛片三级朝国网站| 色婷婷av一区二区三区视频| 精品少妇久久久久久888优播| 国产亚洲av高清不卡| 国产高清激情床上av| 久久精品国产亚洲av高清一级| 色婷婷av一区二区三区视频| av不卡在线播放| 老熟女久久久| 国产av精品麻豆| 亚洲国产av新网站| 久久久久视频综合| 下体分泌物呈黄色| 天天添夜夜摸| 操出白浆在线播放| 丰满人妻熟妇乱又伦精品不卡| 久久久久国产一级毛片高清牌| 国产精品熟女久久久久浪| 女性被躁到高潮视频| 女人被躁到高潮嗷嗷叫费观| 亚洲精品美女久久久久99蜜臀| 电影成人av| 欧美日韩成人在线一区二区| 亚洲欧洲精品一区二区精品久久久| 国产亚洲午夜精品一区二区久久| 一二三四在线观看免费中文在| 久热这里只有精品99| 精品一区二区三卡| a级片在线免费高清观看视频| 精品一区二区三区视频在线观看免费 | 99久久99久久久精品蜜桃| 亚洲少妇的诱惑av| 亚洲第一青青草原| 波多野结衣一区麻豆| 亚洲精品国产一区二区精华液| 人人妻人人添人人爽欧美一区卜| 黄色 视频免费看| 国产精品二区激情视频| 久久精品亚洲av国产电影网| 国产精品偷伦视频观看了| 2018国产大陆天天弄谢| a级毛片黄视频| 天天躁夜夜躁狠狠躁躁| 天堂动漫精品| 啦啦啦 在线观看视频| 久久精品国产a三级三级三级| 日本五十路高清| 丝袜美腿诱惑在线| 在线观看人妻少妇| 在线天堂中文资源库| 欧美精品一区二区免费开放| 两个人看的免费小视频| 国产精品久久久久成人av| av天堂在线播放| 精品国产乱码久久久久久男人| 一二三四社区在线视频社区8| 香蕉国产在线看| 精品福利永久在线观看| 操美女的视频在线观看| 又大又爽又粗| 亚洲情色 制服丝袜| 国产在线一区二区三区精| 久久国产精品大桥未久av| 日本vs欧美在线观看视频| 午夜成年电影在线免费观看| 午夜福利影视在线免费观看| 波多野结衣av一区二区av| 精品免费久久久久久久清纯 | 亚洲avbb在线观看| 久久人妻av系列| 黄色怎么调成土黄色| 咕卡用的链子| 高清毛片免费观看视频网站 | 两性夫妻黄色片| 在线播放国产精品三级| 超碰成人久久| 国产在线观看jvid| 在线观看免费视频网站a站| 亚洲中文av在线| av网站免费在线观看视频| 最近最新中文字幕大全电影3 | 久久国产精品大桥未久av| 国产精品成人在线| 欧美人与性动交α欧美软件| 麻豆国产av国片精品| 十八禁网站网址无遮挡| 精品国产一区二区三区四区第35| 欧美乱妇无乱码| 亚洲国产精品一区二区三区在线| 亚洲,欧美精品.| 欧美+亚洲+日韩+国产| 亚洲精品成人av观看孕妇| av不卡在线播放| 亚洲va日本ⅴa欧美va伊人久久| 在线观看舔阴道视频| 久久ye,这里只有精品| av福利片在线| 两性夫妻黄色片| 在线观看免费午夜福利视频| 91国产中文字幕| 18禁美女被吸乳视频| 18禁美女被吸乳视频| 一级片免费观看大全| 岛国毛片在线播放| 午夜福利欧美成人| 男女床上黄色一级片免费看| av有码第一页| 免费观看av网站的网址| 美女高潮到喷水免费观看| 亚洲精品粉嫩美女一区| 美女午夜性视频免费| 亚洲av美国av| 久久人妻福利社区极品人妻图片| 黄色视频,在线免费观看| 国产精品av久久久久免费| 一区二区日韩欧美中文字幕| 老司机在亚洲福利影院| 下体分泌物呈黄色| 国产亚洲av高清不卡| 在线观看www视频免费| 国产精品1区2区在线观看. | 久久免费观看电影| 国产精品欧美亚洲77777| 免费观看a级毛片全部| 操美女的视频在线观看| 亚洲精品乱久久久久久| 菩萨蛮人人尽说江南好唐韦庄| 久久人妻av系列| 99国产精品一区二区三区| 女人高潮潮喷娇喘18禁视频| 亚洲成人国产一区在线观看| 超色免费av| 三级毛片av免费| 女警被强在线播放| 精品乱码久久久久久99久播| 色94色欧美一区二区| 叶爱在线成人免费视频播放| 国产色视频综合| 欧美成人免费av一区二区三区 | 久久久久久久久久久久大奶| 99热网站在线观看| 最近最新中文字幕大全电影3 | av有码第一页| 久久精品91无色码中文字幕| 无人区码免费观看不卡 | 两个人免费观看高清视频| 女性生殖器流出的白浆| 亚洲av欧美aⅴ国产| 可以免费在线观看a视频的电影网站| 50天的宝宝边吃奶边哭怎么回事| 麻豆乱淫一区二区| 欧美精品高潮呻吟av久久| 日本精品一区二区三区蜜桃| 亚洲精品美女久久久久99蜜臀| 高清黄色对白视频在线免费看| 夜夜爽天天搞| 日本一区二区免费在线视频| av天堂久久9| 美女主播在线视频| 99国产精品一区二区蜜桃av | 精品亚洲成a人片在线观看| 精品亚洲成a人片在线观看| av福利片在线| 中文字幕色久视频| 亚洲第一欧美日韩一区二区三区 | a级毛片在线看网站| 精品久久久久久电影网| 午夜免费鲁丝| 夜夜骑夜夜射夜夜干| 精品人妻1区二区| 99国产精品免费福利视频| 欧美日韩视频精品一区| 亚洲成国产人片在线观看| 我的亚洲天堂| 国产精品亚洲一级av第二区| 女人高潮潮喷娇喘18禁视频| 免费高清在线观看日韩| 女警被强在线播放| 欧美成人免费av一区二区三区 | 欧美亚洲 丝袜 人妻 在线| 亚洲欧洲日产国产| 女人爽到高潮嗷嗷叫在线视频| www.熟女人妻精品国产| 大片免费播放器 马上看| 欧美 日韩 精品 国产| 亚洲熟女毛片儿| 日韩精品免费视频一区二区三区| 中文字幕人妻丝袜制服| 最新在线观看一区二区三区| 免费一级毛片在线播放高清视频 | 丝瓜视频免费看黄片| 国产精品麻豆人妻色哟哟久久| 欧美黄色片欧美黄色片| 99riav亚洲国产免费| 天堂8中文在线网| 日本黄色日本黄色录像| 日韩一卡2卡3卡4卡2021年| 丝袜美足系列| 免费少妇av软件| 老鸭窝网址在线观看| 午夜激情久久久久久久| 久久国产精品影院| 免费看a级黄色片| 丝袜美腿诱惑在线| 人成视频在线观看免费观看| 亚洲成国产人片在线观看| 亚洲色图av天堂| 国产一卡二卡三卡精品| 两性夫妻黄色片| 亚洲av成人一区二区三| 精品人妻1区二区| 交换朋友夫妻互换小说| 精品久久蜜臀av无| av不卡在线播放| 国产免费av片在线观看野外av| 成人黄色视频免费在线看| 美女福利国产在线| 涩涩av久久男人的天堂| 精品福利永久在线观看| 黄色a级毛片大全视频| 亚洲精品在线观看二区| 电影成人av| 国产精品久久电影中文字幕 | 国产片内射在线| 精品一区二区三区视频在线观看免费 | 久久精品国产99精品国产亚洲性色 | 欧美精品av麻豆av| 黄网站色视频无遮挡免费观看| 十八禁网站网址无遮挡| 性少妇av在线| 精品国内亚洲2022精品成人 | 免费在线观看视频国产中文字幕亚洲| 一区福利在线观看| 制服诱惑二区| 在线播放国产精品三级| 变态另类成人亚洲欧美熟女 | 男女免费视频国产| 精品第一国产精品| 国产精品影院久久| 肉色欧美久久久久久久蜜桃| 久久精品国产99精品国产亚洲性色 | 99热网站在线观看| 侵犯人妻中文字幕一二三四区| 人人妻人人爽人人添夜夜欢视频| av福利片在线| 正在播放国产对白刺激| 精品国产亚洲在线| 免费高清在线观看日韩| 正在播放国产对白刺激| 午夜视频精品福利| 国产免费福利视频在线观看| 国产高清videossex| 动漫黄色视频在线观看| 91av网站免费观看| 午夜免费鲁丝| 男女午夜视频在线观看| 天天操日日干夜夜撸| 丰满人妻熟妇乱又伦精品不卡| 国产日韩欧美亚洲二区| 国产福利在线免费观看视频| 制服人妻中文乱码| 国产男靠女视频免费网站| 亚洲人成电影观看| 青青草视频在线视频观看| 成人国产一区最新在线观看| 最新的欧美精品一区二区| 99九九在线精品视频| 欧美变态另类bdsm刘玥| 亚洲人成伊人成综合网2020| av免费在线观看网站| 人人妻人人爽人人添夜夜欢视频| 麻豆国产av国片精品| 王馨瑶露胸无遮挡在线观看| 午夜福利,免费看| 在线观看免费高清a一片| 成人国语在线视频| 亚洲色图av天堂| 国产一区二区激情短视频| 久久这里只有精品19| 黄色视频在线播放观看不卡| 美女高潮到喷水免费观看| 色综合欧美亚洲国产小说| 另类精品久久| 叶爱在线成人免费视频播放| 91大片在线观看| 飞空精品影院首页| 大型av网站在线播放| 亚洲精品久久午夜乱码| 免费黄频网站在线观看国产| 成年人黄色毛片网站| 一本综合久久免费| 深夜精品福利| 精品欧美一区二区三区在线| 美女视频免费永久观看网站| 天天操日日干夜夜撸| 在线观看免费高清a一片| 男女无遮挡免费网站观看| 中文字幕人妻熟女乱码| 曰老女人黄片| 国产成人精品在线电影| √禁漫天堂资源中文www| 久久精品国产a三级三级三级| 亚洲一码二码三码区别大吗| 久久人妻av系列| 日韩 欧美 亚洲 中文字幕| 波多野结衣一区麻豆| 99国产精品一区二区三区| 美女高潮到喷水免费观看| 国产高清videossex| 91成人精品电影| 亚洲天堂av无毛| 九色亚洲精品在线播放| 精品国产乱码久久久久久男人| 国产在线精品亚洲第一网站| 99久久人妻综合| 免费人妻精品一区二区三区视频| 天天躁日日躁夜夜躁夜夜| 日韩欧美一区视频在线观看| e午夜精品久久久久久久| 天堂俺去俺来也www色官网| 一本综合久久免费| 日本黄色日本黄色录像| 大片电影免费在线观看免费| 男人舔女人的私密视频| 精品福利永久在线观看| 免费一级毛片在线播放高清视频 | 国产真人三级小视频在线观看| 制服诱惑二区| 97人妻天天添夜夜摸| 亚洲性夜色夜夜综合| 国产aⅴ精品一区二区三区波| 国产一区有黄有色的免费视频| cao死你这个sao货| 飞空精品影院首页| 成人免费观看视频高清| 多毛熟女@视频| 精品一区二区三卡| 国产单亲对白刺激| 乱人伦中国视频| 啪啪无遮挡十八禁网站| 精品卡一卡二卡四卡免费| 精品视频人人做人人爽| 亚洲熟女精品中文字幕| 国产精品99久久99久久久不卡| 男女下面插进去视频免费观看| 少妇猛男粗大的猛烈进出视频| 1024香蕉在线观看| av网站在线播放免费| 亚洲伊人色综图| 黄频高清免费视频| 午夜日韩欧美国产| 1024香蕉在线观看| 日韩大片免费观看网站| 成人特级黄色片久久久久久久 | 亚洲精品久久成人aⅴ小说| 成人黄色视频免费在线看| 91精品国产国语对白视频| 啦啦啦免费观看视频1| 一区二区av电影网| 飞空精品影院首页| 交换朋友夫妻互换小说| 欧美乱码精品一区二区三区| 日韩欧美一区视频在线观看| 精品久久蜜臀av无| 女人高潮潮喷娇喘18禁视频| 亚洲伊人久久精品综合| 亚洲国产欧美日韩在线播放| 在线观看免费日韩欧美大片| 午夜激情av网站| 国产成人精品久久二区二区91| 国产99久久九九免费精品| 久久毛片免费看一区二区三区| 多毛熟女@视频| 久久国产精品男人的天堂亚洲| 大码成人一级视频| 国产一区有黄有色的免费视频| 亚洲成国产人片在线观看| 亚洲少妇的诱惑av| 三级毛片av免费| 热re99久久精品国产66热6| 久久亚洲真实| 免费日韩欧美在线观看| 精品福利永久在线观看| 水蜜桃什么品种好| 夜夜爽天天搞| 久久精品亚洲熟妇少妇任你| 久久99一区二区三区| 精品少妇久久久久久888优播| 久久av网站| 久久国产精品人妻蜜桃| 久热这里只有精品99| av又黄又爽大尺度在线免费看| 国产精品影院久久| 在线观看免费午夜福利视频| 18禁观看日本| 日韩有码中文字幕| 18禁观看日本| 国产成人一区二区三区免费视频网站| 午夜精品国产一区二区电影| 91国产中文字幕| 另类精品久久| 国产精品 国内视频| √禁漫天堂资源中文www| 国产在线观看jvid| 中文字幕人妻熟女乱码| 丰满饥渴人妻一区二区三| 夜夜爽天天搞| 一区二区三区乱码不卡18| 宅男免费午夜| 国产激情久久老熟女| 自线自在国产av| 亚洲熟女精品中文字幕| 黄色视频在线播放观看不卡| 少妇裸体淫交视频免费看高清 | 美国免费a级毛片| 欧美老熟妇乱子伦牲交| 性少妇av在线| 丁香六月天网| 操出白浆在线播放| 国产精品熟女久久久久浪| 成年动漫av网址| 欧美乱妇无乱码| 国产亚洲精品一区二区www | 日韩有码中文字幕| 久久久精品区二区三区| 一个人免费在线观看的高清视频| 色视频在线一区二区三区| 亚洲精品一卡2卡三卡4卡5卡| 99国产综合亚洲精品| 一区福利在线观看| 免费在线观看完整版高清| 日韩人妻精品一区2区三区| av天堂久久9| www.999成人在线观看| 国产精品 欧美亚洲| 国产又色又爽无遮挡免费看| 国产精品久久电影中文字幕 | 国产老妇伦熟女老妇高清| 十八禁网站网址无遮挡| 国产欧美日韩一区二区精品| 女人爽到高潮嗷嗷叫在线视频| 国产一区有黄有色的免费视频| 热99re8久久精品国产| 黑人巨大精品欧美一区二区mp4| h视频一区二区三区| 午夜精品久久久久久毛片777| 青青草视频在线视频观看| 精品亚洲成国产av| 久久亚洲真实| 欧美乱码精品一区二区三区| 不卡一级毛片| 成年人黄色毛片网站| 在线观看www视频免费| 久久av网站| 免费不卡黄色视频| 国产亚洲av高清不卡| 国产不卡一卡二| 亚洲一区二区三区欧美精品| 国产av国产精品国产| 中文字幕精品免费在线观看视频| 天堂俺去俺来也www色官网| 精品国产一区二区三区久久久樱花| 日本黄色视频三级网站网址 | 最黄视频免费看| 国产一区二区三区在线臀色熟女 | 精品国产一区二区三区久久久樱花| 国产成人啪精品午夜网站| 国产精品久久久久久精品古装| 久久性视频一级片| 亚洲欧美日韩另类电影网站| 嫁个100分男人电影在线观看| 久久婷婷成人综合色麻豆| 久久久久久久精品吃奶| 国产亚洲一区二区精品| 制服诱惑二区| 国产精品亚洲一级av第二区| 成年人黄色毛片网站| 成人国产av品久久久| 菩萨蛮人人尽说江南好唐韦庄| 亚洲欧洲精品一区二区精品久久久| tube8黄色片| 一进一出抽搐动态| 天天影视国产精品| 99久久精品国产亚洲精品| 乱人伦中国视频| 成人三级做爰电影| 国产高清视频在线播放一区| 18禁裸乳无遮挡动漫免费视频| 亚洲成国产人片在线观看| 精品一区二区三卡| 天天添夜夜摸| 国产1区2区3区精品|