• <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 ?

    Microstructure, mechanical properties, and corrosion resistance of an explosively welded Mg-Al composite

    2022-07-12 10:28:56MustfArerBilgeDemirBurkDikiiEminSlur
    Journal of Magnesium and Alloys 2022年4期

    Mustf Arer, Bilge Demir, Burk Dikii, Emin Slur

    a Department of Metallurgical and Materials Engineering, Technology Faculty, Selcuk University, Konya 42075, Turkey

    b Department of Mechanical Engineering, Karabuk University, Karabuk 78100, Turkey

    c Department of Metallurgical and Materials Engineering, Atatürk University, Erzurum 25240, Turkey

    Abstract In this study, an attempt was made to manufacture an AZ31-Al5005 laminated composite by explosive welding.A mixture of ammonium nitrate (90%), fuel oil (5%), and TNT (5%) was used as the explosive.The detonation velocity of the explosive material was approximately 3100 m·s-1.The microstructure and mechanical and corrosion properties of the joint were comparatively investigated.Microstructural characterisation of the joint was conducted by optical microscopy (OM), scanning electron microscopy with energy-dispersive spectroscopy(SEM-EDS), high-resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD).The mechanical properties were determined using micro-Vickers hardness, tensile, and Charpy impact tests.In addition, electrochemical tests were conducted on the AZ31-Al5005 laminated composite and the individual components to determine their corrosion resistance.The corrosion behaviours of the structures were determined in a 3.5% NaCl solution at room temperature using potentiodynamic scanning (PDS).The metallurgical structure and mechanical properties of the joints were within the acceptable limits.

    1.Introduction

    Explosive cladding or welding is a solid-state welding process used to join a wide variety of similar and dissimilar metals and alloys with different physical and mechanical properties.Although this process is classifie as a cold technique,some local melted zones may form at the interface owing to the high-pressure dynamics generated by the explosives[1-3].The unique feature of this welding method is that it can join metals with different melting temperatures.In addition, this method can be used to produce laminated metallic composites with different properties using very different metal combinations.Therefore, the use of a combination of metal sheets and an explosive welding method is considered to be an important process for joining metals [4].

    Numerous attempts have been made to reveal the effects of explosive welding parameters [2]on the microstructure and mechanical properties of explosively welded bimetals,such as stainless steel-carbon steel [5-7], aluminium-steel[3,8,9], and copper-steel [10].However, studies on the explosive welding of magnesium to other metals are limited.Ghaderi et al.[11]attempted to determine the optimum welding conditions for the explosive welding of aluminium to magnesium.Habib et al.[12]reported the explosive welding of titanium to magnesium using underwater shockwaves.The effects of the welding parameters on the weld integrity of explosively welded magnesium-aluminium joints were discussed in another study by Ghaderi et al.[13].The reason for the limited number of studies is probably the poor ductility and formability of magnesium alloys resulting from their hexagonal close-packed (HCP) crystal structure.In explosive welding, the welded metals must have at least 5% elongation.Therefore, the weldability of magnesium alloys by explosions is limited by their mechanical properties [14].

    There are some studies[15-17]on the corrosion properties of explosively welded laminated composites.Kaya[15]investigated the corrosion resistance of aluminium clad to ship steel plates by explosive welding.The neutral salt spray test results showed that cladding aluminium on top of ship steel using explosive welding protected the ship steel against corrosion in a seawater environment.In another study [16], the corrosion behaviours of steel-aluminium composite structures produced via explosive welding were evaluated using immersion tests in NaCl solutions.After the corrosion tests, the metallographic observations revealed that the molten zones during the explosive welding preferentially acted as corrosion initiation points in the joint, and metal losses were mainly observed in these zones.The study showed that corrosion degradation does not depend on the explosive conditions owing to the complete erosion of the molten zones.It has also been reported that an area susceptible to intercrystalline corrosion can form owing to the heat generated and rapid diffusion in the weld zone (or non-diffusion mass transport) during explosive cladding [17].

    Similar to studies on the explosive welding of Mg alloys,studies on the corrosion properties of bimetals produced by explosive welding are limited.However, detailed studies are needed to understand the joining and corrosion damage mechanisms of bimetals with different crystal structures, such as hexagonal close-packed (HCP) and face-centred cubic (FCC)phases, produced by explosive welding.Therefore, the microstructure and interface characteristics, mechanical properties, and corrosion resistance of explosively welded AZ31-Al5005 alloys were investigated in this study.

    2.Experimental procedure

    AZ31 magnesium alloy sheet was used as the flye metal,and 5005 aluminium alloy sheet was used as the parent metal to produce laminated composites in this study.The chemical compositions of the AZ31 and Al5005 alloys are listed in Table 1.

    Table 1The chemical compositions of AZ31 and Al5005 sheets.

    Table 2Tensile test results of the AZ31-Al5005 composite.

    The dimensions of the AZ31 and Al5005 sheets were 150 × 150 × 4 mm3and 150 × 150 × 1.5 mm3, respectively.Rubber layers were used as the buffer zone between both the AZ31 and explosive and the Al5005 and anvil to minimise the deformation of the AZ31 and Al5005 sheets during the explosion.A mixture of ammonium nitrite (90%),fuel oil (5%), and TNT (5%) was used as the explosive.The detonation velocity of the explosive material was approximately 3000-3200 m·s-1.

    The cross section of the joint was ground with increasingly fin sandpaper to remove the cutting traces formed on it.Then,the surfaces were polished with 1 μm diamond paste and ultrasonically cleaned with ethanol.AZ31 was etched in a solution containing 10 ml acetic acid, 5 g picric acid, 10 ml ethanol, and 75 ml distilled water.The microstructural characterisation of the joint was conducted by optical microscopy(OM, NIKON Epiphot 200), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS, Jeol JSM 5600), high-resolution transmission electron microscopy (HRTEM, JEOL JEM-2100), and X-ray diffraction (XRD).

    The mechanical properties were determined using a microhardness tester (LECO DM-400) under a 10 gf load for 15 s.The average values from across the weld interfaces were reported.Tensile and impact tests were performed to determine the strength/elongation and toughness of the laminated composite structure,respectively.The toughness of the AZ31-Al5005 composite was measured by Charpy V-notch tests at+25,0,-25,and-50°C using a DEVOTRANS test machine with a 50Jhammer.

    The corrosion behaviours of the joints and their base metals were determined using the potentiodynamic scanning(PDS) technique at room temperature.The changes in the potential (E) vs.current (I) of the samples were recorded using a potentiostat unit (Gamry, PCI14/750) in a 3.5% NaCl so-lution.Ag/AgCl and Pt wire were used as the reference and counter electrodes,respectively,during the tests.The scan rate of the PDS measurements was 1 mV?s-1.The sample area was approximately 0.5 cm2, and all data were normalised to the surface area.Both the fractured and corroded surfaces were investigated by SEM.

    Fig.2.(a) Wavy interface, (b) mapping and (c) EDS line analysis of the AZ31-Al5005 composite.

    3.Results and discussion

    3.1.Microstructure

    The microstructure of the AZ31 magnesium alloy (before the explosive welding process) used as a flye metal is shown in Fig.1.The AZ31 Mg alloy consisted of almost equiaxedα-Mg grains (Fig.1b).

    Fig.1.The microstructure of AZ31 magnesium alloy:(a)optical micrograph,and (b) histogram of grain size distribution.

    The AZ31-Al5005 laminate composite was produced by an explosive welding technique.Even when precautions were taken(such as annealing before the welding process and using a buffer zone during the explosion), cracks were observed locally on the Mg side because the number of slip systems was insufficien to allow deformation of the Mg sheet under the shock wave generated during explosive welding.

    The microstructure of the welding interface and elemental mapping and line analysis of the AZ31-Al5005 composite produced by explosive welding are shown in Fig.2a-c, respectively.A wavy interface was observed in the explosively welded AZ31-Al5005 composite (Fig.2a).

    The morphology of the interface was wavy (Fig.2a) because the explosive loading was sufficien to produce a wavy interface.Straight and wavy interfaces can be formed between explosively welded materials.Increasing the explosive loading increases the impact energy of the flye plate, which causes a transition from a straight to a wavy interface [5].To further analyse the wavy interface formed by the explosion,EDS mapping analyses were performed primarily for the welding interface region, as illustrated in Fig.3.Although almost the entire interface showed a sharp transition (Figs.3 and 4), partially molten regions (Fig.5) were also observed.The presence of both Mg and Al in the crystal structures at the interface indicates a sharp transition at the junction interface.Fig.4 shows a TEM image and diffraction patterns of the Mg and Al sides of the joining interface shown in Fig.3a.Fig.4a shows a representative HR-TEM micrograph of the AZ31-Al5005 interface transition zone.As shown in the upper area in Fig.4a, the interplanar spacing was measured to be 0.2340 ± 0.010 nm, which matches the (11-21)reflectio of Mg.The lattice spacing calculated from the upper region was 0.2032 ± 0.015 nm, which corresponds to the (200) plane of Al.Nanometric grain boundaries were observed because of the rearrangement of crystallites in different orientations during the explosion.Furthermore, selected area electron diffraction (SAED) indexing was conducted for qualitative phase analysis of the elements in the transition zone,as shown in Fig.4b.The four rings, consisting of continuous diffraction spots, correspond to Mg (-1121), Al (200),Mg (-1120), and Al (311), respectively, in the outward radial direction.

    Fig.3.(a) TEM image of welding interface in the AZ31-Al5005 composite, and (b,c) its elemental mapping analyses.

    Local melted regions in the interface probably formed via melting and solidificatio during explosive welding, in which the kinetic energy between AZ31 and Al5005 during the explosion produced the required melting temperature.Ghaderi et al.[11]reported that despite the high temperatures generated at the interface, the high velocity of the process and immediate heat transfer to the bulk of the materials creates conditions that are insufficien for melting or diffusion.However, they also observed that the eddy regions in which metallurgical changes occurred owing to the re-entrant jet caused localised temperature increases and melting.The compositional changes may have been caused by melting.Zhang et al.[10]observed a diffusion layer in a AZ31B and Al6061 welding interface.They attributed this phenomenon to metallurgical bonding of the interface in the AZ31B/Al6061 composite plates.In this study, intermetallic structures were also observed (Fig.6a and b), which were identifie as Mg3Al2and Mg2Al3via SAED.As shown in the upper side of Fig.6a,the interplanar spacing was measured to be 0.2774 ± 0.010 nm,which is consistent with the (100) reflectio of Mg.The lattice spacing calculated from the lower region in Fig.6a was 0.2290 ± 0.015 nm, which corresponds to the interplanar spacing of the(1222)plane of Mg2Al3.These outcomes agree to a great extent with the XRD results shown in Fig.7.A closer examination of the 40°-60° region of the XRD data showed that traces of some intermetallic phases were visible within the resolution limit of the XRD analysis.Therefore, the XRD results, which are in good agreement with the HRTEM and SAED indexing results, clearly show the formation of intermetallic phases generated by the combined effect of the melting and solidificatio processes.Jonnard et al.[18],Mofi et al.[19], and Wachowski et al.[20]reported the formation of Mg17Al12,Mg3Al2,and Mg2Al3intermetallic phase in Mg-Al alloys and Mg-Al couples.It is thought that the formation of these intermetallic structures is due to melting and subsequent solidification In the TEM investigation, no amorphous structures, which can form owing to the high cooling rates (105-106 °C·s-1) in the melting-solidificatio process, were observed.Paul et al.[21]observed an amorphous structure in carbon or stainless steel/Zr, carbon steel/Ti, and stainless steel/Ta claddings.Nishida et al.[22]reported that the interface of a Ti-stainless steel couple produced by explosive welding had a sharp transition and an amorphous structure in a locally melted-solidifie zone.The HRTEM images(Figs.4 and 6)suggest that the metals joined via metallurgical bonding during explosive welding.

    Two different microstructures were observed in the AZ31 magnesium alloy side near the interface, as shown inFig.8a and b.The firs was adiabatic shear bands (ASB),which occurred only on the AZ31 side near the explosive welding interface and originated from the interface.The second was refine equiaxed grains,including twin structures due to deformation.

    Fig.4.(a) HRTEM image, and (b) diffraction pattern of the transition zone of AZ31-Al5005 interface.

    Fig.7 shows XRD patterns of the original Mg sheet and Mg side of the AZ31-Al5005 composite.After explosive welding, the peaks shifted to lower angles owing to severe plastic deformation.

    3.2.Mechanical properties

    Fig.6.The representative (a) HR-TEM image and (b) SAED pattern of the composite, showing the presence of intermetallic phases.

    The hardness values of the as-received Al5005 and AZ31 were 50 and 78 HV, respectively.After the explosive welding process, the hardness of the AZ31 side of the composite reached 120 HV near the interface, but it gradually decreased to the original hardness away from the interface.Fig.9 shows the change in the hardness of the AZ31-Al5005 composite with the distance from the interface.There was a similar trend in the hardness on the Al5005 side.Severe plastic deformation caused an increase in hardness near the interface.During the explosive welding process, the bottom surface of the flye plate (the Mg sheet) collides with the upper surface of the base metal (the Al side) at a high velocity.Upon impact, thekinetic energy is dissipated as heat through the surfaces of the plates or sheets.However,the increase in temperature is insufficien to recrystallise the interface of the composite, or there is insufficien time for recrystallisation to occur.Therefore,severe cold plastic deformation occurs at the interface, which is the reason for the increased hardness.However, owing tothe kinetic energy of the process, melted-solidifie regions can form locally, as explained in the microstructure section.Therefore, the hardness near these regions can be lower than that away from the interface.

    Fig.5.(a) SEM image of welding interface in the AZ31-Al5005 composite, and (b) its elemental mapping analyses.

    Fig.7.(a) XRD pattern of original Mg sheet and Mg side of AZ31-Al5005 composite, (b) the peaks showing Mg3Al ve Mg2Al intermetallic phases.

    Fig.8.(a) AZ31-Al5005 composite interface, and (b) away from the interface.

    Fig.9.The hardness of the AZ31-Al5005 composite.

    Fig.10.Charpy V-notch impact test results.

    The tensile test results for the AZ31-Al5005 composite are summarised in Table 2.The results illustrate that the tensile strength and yield strength of the composite were lower than those of the individual components owing to the cracks formed during the explosive welding process.It can be seen from Table 2 that the elongation of the composite was lower than that of the AZ31 magnesium alloy and similar to that of the Al5005 alloy.

    Table 3Corrosion parameters of the samples calculated from PDS curves.

    The impact energies of the AZ31-Al5005 composite varied between 12 and 13Jat all temperatures.Decreasing the temperature did not cause a significan change in the impact strength.For body-centred cubic(BCC)metals,decreasing the temperature causes a transition from ductile to brittle fracture.The main reason for this, and the reason it does not occur in FCC and HCP metals, is that BCC metals do not have closed-pack planes.Atomic vibrations affect the deformation (slipping) of metals, particularly at low temperatures.However, with decreasing temperature, atomic vibrations decrease, and their contribution to slip is limited.Because BCC metals do not contain close-packed atomic planes, this phenomenon is more evident.While atomic vibrations are limited at low temperatures in FCC and HCP metals, the high atomic density of these crystalline metals in the close-packed planes minimises the negative effect of low vibrations.As a result,slipping is the most prominent ductile fracture feature and plastic deformation mechanism in metals.Because the contribution of atomic vibrations to slip at low temperatures is limited,BCC metals show brittle fracture at low temperatures,while they show ductile fracture at higher temperatures [23].In addition, the number of slip systems in HCP metals is low.Thus, ductile fracture does not occur in metals with this crystal structure.

    The fracture surfaces of the Mg and Al sides of the composite showed the same characteristics at all temperatures(Fig.11).The Al5005 surface had dimples, while there were no dimples on the Mg side.The dimples are evidence of the slip mechanism in metallic materials.Because the number of slip systems in HCP metals is very low compared to thosein BCC and FCC crystalline metals, the Mg alloy fractured without significan plastic deformation.

    3.3.Corrosion test results

    The polarisation curves (PDS) of the original metals and explosively welded composite materials in 3.5% NaCl are presented in Fig.12.Some important corrosion parameters calculated from these curves are listed in Table 3.

    Undoubtably, aluminium and magnesium are popular because of their low densities.However, magnesium alloys are not as widely used as aluminium alloys, primarily because of their high sensitivity to corrosion, which is a major drawback that limits the widespread use of magnesium alloys in industry.However, studies on Mg alloys with high specifi strength and corrosion resistance have increased in parallel with technological developments [24,25].

    Magnesium alloys have very poor corrosion resistance when exposed to aggressive environments rich in chloride ions, although they are resistant to atmospheric corrosion because of the protective oxide layer that typically forms on their surface.Numerous different corrosion mechanisms can be observed for Al and Mg alloys according to their alloying components or thermomechanical history.The most common mechanisms are pitting and transgranular corrosion.However,galvanic corrosion occurs on Mg when Mg is in contact with another metal that has a nobler electrochemical potential than that of Mg [26].Galvanic corrosion is also known as bimetallic corrosion(or dissimilar metal corrosion)and should be expected in explosively welded materials.Heavy galvanic corrosion marks were observed on the explosively welded AZ31-Al5005 structure in this study (Fig.13).

    It is well known that corrosion reactions occur at the inflectio points of the PDS curves of materials, which also correspond to theEcorrvalue.In this study, the steady-state potentials of the original AZ31 and Al5005 alloys were calculated to be -1510 and -733 mV, respectively (Table 3).The large difference between theEcorrvalues of the original materials triggered galvanic corrosion in the explosively welded structure.Thus, the corrosion rate of the explosively welded structure increased owing to the high galvanic coupling between the Al5005 and AZ31 alloys (Table 3).

    The corroded surfaces of the explosively welded structures at different polarisation levels are presented in Fig.14.

    Fig.11.The fracture surface of the AZ31-Al5005 composite.

    Fig.12.Potentiodynamic scanning (PDS) curves of the samples in 3.5%NaCl.

    Fig.13.Formed galvanic couplings between Al5005 and AZ31 composite structure after the corrosion tests.

    Above the inflectio points, the dissolution of the AZ31 matrix can be described by the Mg + 2e-→Mg2+anodic reaction.In this stage (Fig.14a), the AZ31 side of the explosively welded metal corroded preferentially because its electrode potential was lower than that of Al5005.Corrosion began at the Al5005/AZ31 interface (marked with an arrow in Fig.14a).The decomposition of alloying elements in the orig-inal materials in these regions was inevitable because of the high temperatures generated at the interface during the welding process,which led to the formation of intermetallic phases(Figs.7 and 8).The cathodic character of the intermetallic compounds in the interface, such as theβphase, also contributed to the corrosion behaviour [26].These compounds increased the local cathode area in the interface.Corrosion propagated into the Mg side (Fig.14b) with increasing polarisation level.A Mg(OH)2-based oxide layer formed on AZ31.However, the magnesium oxide layer was very porous and fragile.In addition, the layer only provided partial protection owing to the occurrence of breaks and the porous structure of the layer (Fig.14c) [27,28].Thus, the layer was exfoliated from the surface owing to leakage of the electrolyte underneath the layer.Consequently, more in-depth oxide film formed on the AZ31 surface, as shown in Fig.14d-f.

    Fig.14.The corroded surfaces of the explosively welded structure during the different polarization levels.

    4.Conclusions

    While different aspects of Mg and Al alloys were examined extensively in the context of the explosive welding process, the interface characteristics and corrosion properties of bimetals produced by this procedure seem to have received only cursory attention in the open literature.Therefore, the primary purpose of this study is to investigate microstructure, mechanical, and corrosion properties of joining interfaces of explosively welded AZ31 and Al5005 sheets within the framework of process-structure-property-performance correlation.For this purpose, the AZ31/Al5005 bimetal composites were successfully produced via explosive welding.The interfacial microstructure evolution, mechanical properties, and corrosion resistance of explosively welded bimetal composites were thoroughly characterized by SEM, XRD, HR-TEM, optic microscopy, Vickers hardness, tensile, Charpy impact, and corrosion tests.The key finding and the concluded remarks could be summarized as follows.

    ·Explosive welding has been advanced with various applications in the manufacturing industry.The process has found chiefl commercial production in large sheets/plates/tubes/pipes joining one similar or dissimilar metals on another, especially for the automotive industry and power plants.Explosive welding employed in this study can be used to join the AZ31 Mg and Al5005 alloys.

    ·Considering microstructural evaluation, a wavy interface formed between the AZ31 and Al5005 alloys after explosive welding.Adiabatic shear bands and equiaxed fin grains, including twin structures due to deformation, were observed on the AZ31 magnesium side near the interface.

    ·Metallographic observations showed that there was a sharp transition from the Mg side to the Al side and that intermetallic phases (such as Mg2Al3and Mg3Al2) formed at the interface.

    ·It was found that there was both a sharp transition from two different metal sides to the other, as well as a transition with intermetallic phase formation, at the interface formed after explosive welding process.Experimental results and conducted detailed analyses showed a reasonable agreement with each other.

    ·According to mechanical characterization, the hardness of the AZ31 and Al5005 sides of the composite decreased to the original hardness away from the interface.Tensile test results showed that the explosively welded AZ31-Al5005 structure had an acceptable yield strength, tensile strength,and elongation.The toughness of the composite did not vary with temperatures.

    ·As expected, bimetallic corrosion occurred at the explosively welded interfaces.Heavy galvanic corrosion marks were also observed by SEM at the interfaces after the corrosion tests.

    ·The corrosion rate of the explosively welded structure increased owing to the high galvanic coupling between the Al5005 and AZ31 alloys.

    ·The corrosion behaviour of the AZ31-Al5005 composite in 3.5% NaCl was similar to that of AZ31.However, the corrosion potential of the explosively welded composite structure was nobler (+250 mV) compared to that of the AZ31 alloy.

    ·On the basis of the above discourses,this study's outcomes revealed that the interface characteristic was a critical effect on the microstructure,mechanical,and corrosion properties of end products, which still remains a blind spot in the available literature regarding explosively welded Al-Mg bimetallic composite systems.

    Acknowledgements

    Authors thank the MKE Barutsan Company (Turkey) for valuable contributions to the explosive welding process of the materials.

    欧美乱色亚洲激情| 老司机在亚洲福利影院| 久久久国产精品麻豆| 麻豆成人av在线观看| 免费在线观看完整版高清| 99久久99久久久精品蜜桃| 最近最新免费中文字幕在线| 精品电影一区二区在线| 最新在线观看一区二区三区| 99在线人妻在线中文字幕| 亚洲五月色婷婷综合| 午夜福利免费观看在线| 色播在线永久视频| 在线观看日韩欧美| 国内少妇人妻偷人精品xxx网站 | 最好的美女福利视频网| 日韩欧美免费精品| 亚洲一卡2卡3卡4卡5卡精品中文| 免费在线观看亚洲国产| 色哟哟哟哟哟哟| 欧美久久黑人一区二区| 国产精品 国内视频| 国产野战对白在线观看| 成年免费大片在线观看| 国产黄片美女视频| 国产av一区二区精品久久| 色综合婷婷激情| 欧美日韩福利视频一区二区| 亚洲国产精品sss在线观看| 夜夜躁狠狠躁天天躁| 亚洲精品一区av在线观看| 亚洲avbb在线观看| 国产精品爽爽va在线观看网站 | 色尼玛亚洲综合影院| 在线观看免费午夜福利视频| 久久热在线av| 国产一区二区三区视频了| a在线观看视频网站| 一本大道久久a久久精品| 午夜福利18| e午夜精品久久久久久久| 亚洲精品在线观看二区| 久久午夜亚洲精品久久| 人妻久久中文字幕网| 国产av在哪里看| www.熟女人妻精品国产| 久久天躁狠狠躁夜夜2o2o| 欧美黑人精品巨大| 黑人巨大精品欧美一区二区mp4| 校园春色视频在线观看| 午夜福利一区二区在线看| 两性午夜刺激爽爽歪歪视频在线观看 | 亚洲在线自拍视频| 91av网站免费观看| 美女免费视频网站| 超碰成人久久| 精品欧美一区二区三区在线| 性色av乱码一区二区三区2| 自线自在国产av| 大型黄色视频在线免费观看| aaaaa片日本免费| 国产成人系列免费观看| 最近最新免费中文字幕在线| 午夜a级毛片| 成人18禁在线播放| 久久中文字幕人妻熟女| 美女大奶头视频| 久久久久免费精品人妻一区二区 | 欧美激情久久久久久爽电影| 97超级碰碰碰精品色视频在线观看| 听说在线观看完整版免费高清| 欧美一级a爱片免费观看看 | 中出人妻视频一区二区| 日本免费a在线| 欧美三级亚洲精品| 亚洲av片天天在线观看| 久99久视频精品免费| 美女高潮喷水抽搐中文字幕| 亚洲中文日韩欧美视频| 久久久久久九九精品二区国产 | 男人的好看免费观看在线视频 | 色av中文字幕| 亚洲中文字幕一区二区三区有码在线看 | 亚洲人成电影免费在线| 久久人人精品亚洲av| 女人被狂操c到高潮| a级毛片在线看网站| www日本黄色视频网| 精品欧美一区二区三区在线| 制服丝袜大香蕉在线| 精品不卡国产一区二区三区| 色综合欧美亚洲国产小说| 欧美日韩亚洲综合一区二区三区_| 97人妻精品一区二区三区麻豆 | 色综合欧美亚洲国产小说| 亚洲五月婷婷丁香| 亚洲午夜精品一区,二区,三区| 99精品久久久久人妻精品| 淫秽高清视频在线观看| 村上凉子中文字幕在线| 香蕉久久夜色| 一卡2卡三卡四卡精品乱码亚洲| 国产成人精品无人区| 欧美黑人精品巨大| 一边摸一边做爽爽视频免费| 人人澡人人妻人| 桃色一区二区三区在线观看| 亚洲人成77777在线视频| 亚洲五月色婷婷综合| 国产片内射在线| 麻豆成人午夜福利视频| 国产伦人伦偷精品视频| 久久精品国产亚洲av香蕉五月| 亚洲中文日韩欧美视频| 性欧美人与动物交配| 成人亚洲精品一区在线观看| 韩国精品一区二区三区| 亚洲一区二区三区不卡视频| 久久久久久亚洲精品国产蜜桃av| 精品免费久久久久久久清纯| 他把我摸到了高潮在线观看| 色哟哟哟哟哟哟| 十八禁人妻一区二区| 国产av一区二区精品久久| 亚洲一区二区三区色噜噜| 黄色a级毛片大全视频| 女警被强在线播放| 国产成人精品无人区| 99re在线观看精品视频| 欧美日本亚洲视频在线播放| 久久精品91蜜桃| 色在线成人网| 久久久水蜜桃国产精品网| 色老头精品视频在线观看| 99国产极品粉嫩在线观看| 亚洲成人久久爱视频| 久久婷婷人人爽人人干人人爱| 又黄又粗又硬又大视频| 人人澡人人妻人| 色综合欧美亚洲国产小说| 18禁黄网站禁片午夜丰满| 亚洲国产欧洲综合997久久, | 亚洲熟女毛片儿| 亚洲成国产人片在线观看| 狠狠狠狠99中文字幕| 欧美黑人欧美精品刺激| 啦啦啦免费观看视频1| 欧美亚洲日本最大视频资源| 欧美不卡视频在线免费观看 | 国产成+人综合+亚洲专区| 麻豆成人午夜福利视频| 亚洲国产欧美一区二区综合| 少妇裸体淫交视频免费看高清 | 91麻豆精品激情在线观看国产| 2021天堂中文幕一二区在线观 | 老司机在亚洲福利影院| 亚洲 欧美一区二区三区| 成人国语在线视频| 最近在线观看免费完整版| 亚洲欧美一区二区三区黑人| 亚洲,欧美精品.| 国产成人欧美| 一边摸一边做爽爽视频免费| 国产精品1区2区在线观看.| 欧美不卡视频在线免费观看 | 美女高潮到喷水免费观看| 精品不卡国产一区二区三区| 91老司机精品| 亚洲人成伊人成综合网2020| 亚洲七黄色美女视频| 亚洲精品色激情综合| 成人三级黄色视频| 成人av一区二区三区在线看| 欧美中文综合在线视频| 啪啪无遮挡十八禁网站| 国产爱豆传媒在线观看 | 免费高清视频大片| 国产视频一区二区在线看| 精品卡一卡二卡四卡免费| 国内久久婷婷六月综合欲色啪| 母亲3免费完整高清在线观看| 深夜精品福利| 亚洲第一av免费看| 999久久久精品免费观看国产| 欧美中文日本在线观看视频| 在线观看免费午夜福利视频| 国产精品 国内视频| 淫秽高清视频在线观看| 国产高清激情床上av| 久久久久亚洲av毛片大全| 免费在线观看日本一区| 中文字幕人妻丝袜一区二区| 黑人操中国人逼视频| 日韩一卡2卡3卡4卡2021年| 宅男免费午夜| 亚洲国产精品999在线| 国内揄拍国产精品人妻在线 | 窝窝影院91人妻| 精品久久久久久久末码| 精品国产美女av久久久久小说| 波多野结衣高清无吗| 精品一区二区三区视频在线观看免费| 欧美日韩精品网址| 91在线观看av| 国产亚洲精品综合一区在线观看 | 亚洲成人精品中文字幕电影| 日本黄色视频三级网站网址| 精品久久蜜臀av无| 中文字幕另类日韩欧美亚洲嫩草| 亚洲 国产 在线| 免费av毛片视频| 午夜两性在线视频| 成年版毛片免费区| 一级黄色大片毛片| 黑人巨大精品欧美一区二区mp4| 黄片播放在线免费| 老司机福利观看| 久久久久国产一级毛片高清牌| 久久久国产成人精品二区| 两性夫妻黄色片| 亚洲色图 男人天堂 中文字幕| 国内毛片毛片毛片毛片毛片| 午夜福利在线在线| 自线自在国产av| 神马国产精品三级电影在线观看 | 成人免费观看视频高清| videosex国产| videosex国产| 91av网站免费观看| 亚洲精品美女久久av网站| 一边摸一边做爽爽视频免费| 欧美日韩瑟瑟在线播放| 国产伦在线观看视频一区| 国产又黄又爽又无遮挡在线| 国产人伦9x9x在线观看| 国产aⅴ精品一区二区三区波| 天堂影院成人在线观看| 欧美人与性动交α欧美精品济南到| 在线永久观看黄色视频| 中文亚洲av片在线观看爽| 婷婷精品国产亚洲av| 亚洲五月色婷婷综合| 一二三四在线观看免费中文在| 欧美成人免费av一区二区三区| aaaaa片日本免费| xxxwww97欧美| 国产日本99.免费观看| 老司机福利观看| 亚洲国产精品久久男人天堂| 中文字幕最新亚洲高清| 久久久久久久久免费视频了| e午夜精品久久久久久久| 久久久久国内视频| 久久久精品欧美日韩精品| 1024香蕉在线观看| 免费高清视频大片| 国产高清激情床上av| 91成人精品电影| 亚洲国产毛片av蜜桃av| 午夜影院日韩av| 精华霜和精华液先用哪个| 少妇被粗大的猛进出69影院| 国产欧美日韩精品亚洲av| 久久久国产精品麻豆| 国产一区二区三区在线臀色熟女| avwww免费| 婷婷精品国产亚洲av| 亚洲熟女毛片儿| 老司机靠b影院| 黄色 视频免费看| 在线观看www视频免费| 欧美三级亚洲精品| 午夜福利高清视频| 久久婷婷人人爽人人干人人爱| 日韩精品免费视频一区二区三区| 欧美激情久久久久久爽电影| 岛国在线观看网站| 久久久久国产精品人妻aⅴ院| 少妇熟女aⅴ在线视频| 超碰成人久久| 国产精品免费视频内射| 白带黄色成豆腐渣| 欧美不卡视频在线免费观看 | 级片在线观看| 非洲黑人性xxxx精品又粗又长| 人人妻人人澡人人看| 成人国语在线视频| 久久中文字幕人妻熟女| 一个人免费在线观看的高清视频| 久久久久久国产a免费观看| 亚洲自拍偷在线| 国产99久久九九免费精品| 99久久精品国产亚洲精品| 香蕉丝袜av| 黄频高清免费视频| 亚洲aⅴ乱码一区二区在线播放 | 亚洲欧洲精品一区二区精品久久久| 可以在线观看的亚洲视频| 99久久国产精品久久久| 久久午夜亚洲精品久久| 热99re8久久精品国产| 中文字幕另类日韩欧美亚洲嫩草| 一夜夜www| 久久狼人影院| 久久婷婷人人爽人人干人人爱| 巨乳人妻的诱惑在线观看| 精品电影一区二区在线| 神马国产精品三级电影在线观看 | 非洲黑人性xxxx精品又粗又长| 国产亚洲欧美98| 在线观看免费午夜福利视频| 中文字幕精品亚洲无线码一区 | 亚洲精品久久成人aⅴ小说| 国产成年人精品一区二区| 十八禁网站免费在线| 一个人免费在线观看的高清视频| 免费观看人在逋| 亚洲黑人精品在线| 欧美人与性动交α欧美精品济南到| x7x7x7水蜜桃| 国产人伦9x9x在线观看| 窝窝影院91人妻| 免费在线观看视频国产中文字幕亚洲| 男人舔奶头视频| 老汉色av国产亚洲站长工具| 国产成人影院久久av| 午夜久久久在线观看| 久久青草综合色| 麻豆一二三区av精品| 亚洲专区字幕在线| 国产99白浆流出| 亚洲真实伦在线观看| 欧美激情 高清一区二区三区| 国产午夜精品久久久久久| 欧美zozozo另类| 日本一区二区免费在线视频| 午夜精品在线福利| 久久久久久亚洲精品国产蜜桃av| 午夜成年电影在线免费观看| 国产精品一区二区精品视频观看| 高清在线国产一区| 亚洲国产中文字幕在线视频| 国产精品电影一区二区三区| 看黄色毛片网站| 国产免费男女视频| 国产精品免费视频内射| 黄网站色视频无遮挡免费观看| 免费在线观看影片大全网站| 中文字幕人成人乱码亚洲影| 免费电影在线观看免费观看| a级毛片a级免费在线| 国产精品久久久久久人妻精品电影| 久久精品成人免费网站| 久久久久久久精品吃奶| 制服诱惑二区| 老司机午夜福利在线观看视频| 高潮久久久久久久久久久不卡| 最新在线观看一区二区三区| 国产精品永久免费网站| 欧美一级毛片孕妇| 高潮久久久久久久久久久不卡| 757午夜福利合集在线观看| 欧美一级毛片孕妇| 欧美久久黑人一区二区| 亚洲va日本ⅴa欧美va伊人久久| 一级毛片女人18水好多| 一级作爱视频免费观看| 在线观看免费日韩欧美大片| 人人妻人人澡人人看| 欧美一级毛片孕妇| 国产久久久一区二区三区| 成人一区二区视频在线观看| 麻豆一二三区av精品| 免费在线观看视频国产中文字幕亚洲| 国产精品1区2区在线观看.| 日韩精品青青久久久久久| 91麻豆精品激情在线观看国产| 亚洲成av片中文字幕在线观看| 国产精品自产拍在线观看55亚洲| 国产成人av教育| 久久 成人 亚洲| 欧美一区二区精品小视频在线| 国产精品九九99| 久99久视频精品免费| 久久 成人 亚洲| 亚洲专区中文字幕在线| 久久久水蜜桃国产精品网| 国产真实乱freesex| 高潮久久久久久久久久久不卡| 精品不卡国产一区二区三区| 国产精品久久久久久精品电影 | 精品久久蜜臀av无| 国产亚洲精品av在线| 国产野战对白在线观看| 天天添夜夜摸| 非洲黑人性xxxx精品又粗又长| 午夜日韩欧美国产| 老司机靠b影院| 日本 av在线| 黄色视频,在线免费观看| 久久久国产精品麻豆| 自线自在国产av| 亚洲欧美日韩高清在线视频| 午夜福利在线观看吧| 动漫黄色视频在线观看| 在线观看66精品国产| av在线播放免费不卡| 一区二区三区精品91| 精品高清国产在线一区| 免费在线观看影片大全网站| 黄色视频,在线免费观看| 可以在线观看的亚洲视频| 成人永久免费在线观看视频| 午夜福利一区二区在线看| 丝袜人妻中文字幕| 欧美最黄视频在线播放免费| 亚洲av成人不卡在线观看播放网| 亚洲精品中文字幕一二三四区| www国产在线视频色| 白带黄色成豆腐渣| 亚洲av成人av| 两人在一起打扑克的视频| 老熟妇乱子伦视频在线观看| 免费电影在线观看免费观看| bbb黄色大片| 757午夜福利合集在线观看| www.999成人在线观看| aaaaa片日本免费| av免费在线观看网站| 欧美激情极品国产一区二区三区| 欧美中文日本在线观看视频| 在线观看免费视频日本深夜| 色综合站精品国产| 成年女人毛片免费观看观看9| 在线观看免费视频日本深夜| 亚洲av五月六月丁香网| 最好的美女福利视频网| 免费人成视频x8x8入口观看| 亚洲人成网站高清观看| 男人舔奶头视频| av视频在线观看入口| 91老司机精品| 国产亚洲精品第一综合不卡| 狠狠狠狠99中文字幕| 中文在线观看免费www的网站 | 欧美精品亚洲一区二区| 亚洲精品色激情综合| 国产视频内射| 白带黄色成豆腐渣| 国产午夜精品久久久久久| 国产亚洲欧美98| 麻豆成人av在线观看| 亚洲精品粉嫩美女一区| 国产成人欧美在线观看| 侵犯人妻中文字幕一二三四区| 一二三四社区在线视频社区8| 国产亚洲欧美98| 亚洲成人免费电影在线观看| 视频区欧美日本亚洲| 可以免费在线观看a视频的电影网站| 一区二区三区激情视频| 免费高清视频大片| 亚洲国产中文字幕在线视频| 波多野结衣高清无吗| 91国产中文字幕| 国产在线精品亚洲第一网站| 亚洲av成人不卡在线观看播放网| 成在线人永久免费视频| √禁漫天堂资源中文www| 亚洲全国av大片| 亚洲国产精品成人综合色| 中文字幕最新亚洲高清| 丝袜在线中文字幕| 满18在线观看网站| 两个人看的免费小视频| 亚洲自拍偷在线| 男人的好看免费观看在线视频 | 精品一区二区三区av网在线观看| 日本五十路高清| 十八禁人妻一区二区| 看黄色毛片网站| 草草在线视频免费看| 午夜精品久久久久久毛片777| 国产亚洲精品av在线| 国产免费av片在线观看野外av| 可以在线观看的亚洲视频| 亚洲午夜精品一区,二区,三区| 1024香蕉在线观看| 老司机午夜十八禁免费视频| 99国产精品一区二区三区| 国产欧美日韩精品亚洲av| 婷婷丁香在线五月| 每晚都被弄得嗷嗷叫到高潮| 欧美成人性av电影在线观看| 50天的宝宝边吃奶边哭怎么回事| 波多野结衣av一区二区av| 亚洲色图 男人天堂 中文字幕| 99国产精品一区二区三区| 美女高潮喷水抽搐中文字幕| 久久久精品国产亚洲av高清涩受| 亚洲一区中文字幕在线| 欧美av亚洲av综合av国产av| 麻豆av在线久日| 久久久久精品国产欧美久久久| 午夜免费成人在线视频| 国产成人精品无人区| 国产成人欧美在线观看| 黑人巨大精品欧美一区二区mp4| 国产真人三级小视频在线观看| 少妇裸体淫交视频免费看高清 | 亚洲精品中文字幕一二三四区| 亚洲人成网站高清观看| 久久国产精品男人的天堂亚洲| 别揉我奶头~嗯~啊~动态视频| 女性被躁到高潮视频| 久久久水蜜桃国产精品网| 亚洲男人的天堂狠狠| 婷婷精品国产亚洲av在线| 午夜福利视频1000在线观看| 岛国在线观看网站| 亚洲性夜色夜夜综合| 久久青草综合色| 午夜免费观看网址| 91麻豆av在线| av天堂在线播放| 国产欧美日韩一区二区精品| av免费在线观看网站| 搡老妇女老女人老熟妇| 国产成人精品久久二区二区免费| 男女床上黄色一级片免费看| 色综合欧美亚洲国产小说| 女人高潮潮喷娇喘18禁视频| 国产欧美日韩一区二区精品| av免费在线观看网站| 国产精品自产拍在线观看55亚洲| 亚洲在线自拍视频| 日韩欧美一区视频在线观看| 热99re8久久精品国产| 亚洲五月色婷婷综合| 亚洲一码二码三码区别大吗| 一区二区三区国产精品乱码| 日本精品一区二区三区蜜桃| 国产成人啪精品午夜网站| 人人妻人人澡欧美一区二区| 可以在线观看的亚洲视频| 久热爱精品视频在线9| 亚洲av第一区精品v没综合| 欧美日本视频| 久久香蕉国产精品| 精品国产乱子伦一区二区三区| 一进一出好大好爽视频| 亚洲avbb在线观看| 亚洲国产精品999在线| 午夜老司机福利片| 久久久久久九九精品二区国产 | a级毛片在线看网站| 成人国产综合亚洲| 欧美日韩乱码在线| 国产亚洲精品av在线| 美女高潮到喷水免费观看| 50天的宝宝边吃奶边哭怎么回事| 在线永久观看黄色视频| 国产激情久久老熟女| 美女午夜性视频免费| 精品欧美一区二区三区在线| 色在线成人网| 国产日本99.免费观看| 久久久久久九九精品二区国产 | 在线观看午夜福利视频| 又紧又爽又黄一区二区| 18美女黄网站色大片免费观看| 成人国产综合亚洲| cao死你这个sao货| 曰老女人黄片| 亚洲aⅴ乱码一区二区在线播放 | 精品国产国语对白av| 久久久国产精品麻豆| 在线国产一区二区在线| 国产精品日韩av在线免费观看| 脱女人内裤的视频| 亚洲精品美女久久av网站| 亚洲欧美日韩高清在线视频| 国产精品二区激情视频| 国产av一区在线观看免费| 国产免费av片在线观看野外av| 亚洲男人的天堂狠狠| 一区二区日韩欧美中文字幕| 欧洲精品卡2卡3卡4卡5卡区| 97人妻精品一区二区三区麻豆 | 亚洲中文日韩欧美视频| 久久久久久大精品| 成人精品一区二区免费| 成人亚洲精品一区在线观看| 午夜日韩欧美国产| 日韩视频一区二区在线观看| 国产成人精品久久二区二区免费| 亚洲狠狠婷婷综合久久图片| 久久久久久久久中文| 亚洲熟妇熟女久久| 高清在线国产一区| 国产高清激情床上av| 国产高清videossex| 18禁国产床啪视频网站| 高清在线国产一区| 久久天堂一区二区三区四区| 亚洲人成网站高清观看| 亚洲熟妇中文字幕五十中出| 日韩大尺度精品在线看网址| 美女高潮到喷水免费观看| 精品卡一卡二卡四卡免费| 亚洲无线在线观看| 成人一区二区视频在线观看| 色综合亚洲欧美另类图片| 久久人妻av系列| 国产精品免费一区二区三区在线|