In this work,a new treatment method combining ultrasonic vibration with FeCoNiCrCu high entropy alloy(HEA)coating was used to prepared Al/Mg bimetal through the lost foam compound casting.The effects of composite trea...In this work,a new treatment method combining ultrasonic vibration with FeCoNiCrCu high entropy alloy(HEA)coating was used to prepared Al/Mg bimetal through the lost foam compound casting.The effects of composite treatment involving ultrasonic vibration and HEA coating on interfacial microstructure and mechanical properties of Al/Mg bimetal were studied.Results demonstrate that the interface thickness of the Al/Mg bimetal with composite treatment significantly decreases to only 26.99%of the thickness observed in the untreated Al/Mg bimetal.The HEA coating hinders the diffusion between Al and Mg,resulting the significant reduction in Al/Mg intermetallic compounds in the interface.The Al/Mg bimetal interface with composite treatment is composed of Al_(3)Mg_(2)and Mg_(2)Si/AlxFeCoNiCrCu+FeCoNiCrCu/δ-Mg+Al_(12)Mg_(17)eutectic structures.The interface resulting from the composite treatment has a lower hardness than that without treatment.The acoustic cavitation and acoustic streaming effects generated by ultrasonic vibration promote the diffusion of Al elements within the HEA coating,resulting in a significant improvement in the metallurgical bonding quality on the Mg side.The fracture position shifts from the Mg side of the Al/Mg bimetal only with HEA coating to the Al side with composite treatment.The shear strength of the Al/Mg bimetal increases from 32.16 MPa without treatment to 63.44 MPa with ultrasonic vibration and HEA coating,increasing by 97.26%.展开更多
Mg/Cu bimetal composites were prepared by compound casting method, and the microstructure evolution, phase constitution and bonding strength at the interface were investigated.It is found that a good metallurgical bon...Mg/Cu bimetal composites were prepared by compound casting method, and the microstructure evolution, phase constitution and bonding strength at the interface were investigated.It is found that a good metallurgical bonding can be achieved at the interface of Mg and Cu,which consists of two sub-layers,i.e.,layer I with 30μm on the copper side composed of Mg2Cu matrix phase, on which a small amount of dendritic MgCu2 phase was randomly distributed;layerⅡ with 140μm on the magnesium side made up of the lamellar nano-eutectic network Mg2Cu+(Mg) and a small amount of detached Mg2Cu phase. The average interfacial shear strength of the bimetal composite is measured to be 13 MPa.This study provides a new fabrication process for the application of Mg/Cu bimetal composites as the hydrogen storage materials.展开更多
In this work,a vibration was applied in the preparation of the Mg/Al bimetal by a novel compound casting in order to improve the mechanical properties of the Mg/Al bimetal,and the effect of the vibration on the interf...In this work,a vibration was applied in the preparation of the Mg/Al bimetal by a novel compound casting in order to improve the mechanical properties of the Mg/Al bimetal,and the effect of the vibration on the interfacial microstructure and mechanical properties of the Mg/Al bimetal was investigated.The results indicated that the vibration had a significant effect on the interfacial microstructure and mechanical properties of the Mg/Al bimetal,but it did not change the phase compositions of the interface,which was composed of layerⅠ(Al3Mg2+Mg2Si),layerⅡ(Al_(12)Mg_(17)+Mg_(2)Si)and layerⅢ(Al_(12)Mg_(17)/δ-Mg).Without vibration,the Mg_(2)Si phase with a needle-like morphology mainly aggregated in the layerⅡof the interface.After the application of the vibration,the SEM and EBSD analysis results showed that the Mg_(2)Si and Al3Mg2phases in the interface were obviously refined,and the distribution of the Mg_(2)Si became more uniform,due to the strong forced convection of the molten metal resulting from the vibration.The TEM analysis indicated that the interface between the A_(l3)Mg_(2) and Mg_(2)Si phases was non-coherent,suggesting the Mg_(2)Si particles cannot act as a heterogeneous nucleation base during the solidification process of the interface.Compared to the Mg/Al bimetal without vibration,the shear strength of the Mg/Al bimetal with vibration increased by about 50%from 31.7 MPa on average to 47.5 MPa,and the hardness of the layer I of the interface increased,and the hardness of the layerⅢdecreased.The fracture surface transformed from a flat fracture morphology without vibration to an irregular zigzag fracture morphology.展开更多
Soldering aluminum alloys at low temperature have great potential to avoid softening of base metals.Pure Al was solderedwith pure tin assisted by ultrasound.The influence of primaryα(Al)on the microstructure of Al/Sn...Soldering aluminum alloys at low temperature have great potential to avoid softening of base metals.Pure Al was solderedwith pure tin assisted by ultrasound.The influence of primaryα(Al)on the microstructure of Al/Sn interface and its bonding strengthwas studied.It is found that the primaryα(Al)in liquid tin tends to be octahedron enclosed by Al{111}facet with the lowest surfacefree energy and growth rate.The ultrasonic action could increase the nucleation rate and refine the particles of primaryα(Al).For thelonger ultrasonic and holding time,a large amount of the octahedral primaryα(Al)particles crystallize at the Al/Sn interface.Thebonding interface exhibits the profile of rough dentation,resulting in an increment of bonding interface area and the effect ofmechanical occlusion.The bonding strength at interface could reach63MPa with ultrasonic time of40s and holding time of10min.展开更多
CBN-AlN composite abrasive grits and AISI 1045 steel were brazed using Ag-Cu-Ti active filler alloy by heating up to the temperature of 890,900 and 920 ℃,respectively,and then held at the temperature for 8 min.Optica...CBN-AlN composite abrasive grits and AISI 1045 steel were brazed using Ag-Cu-Ti active filler alloy by heating up to the temperature of 890,900 and 920 ℃,respectively,and then held at the temperature for 8 min.Optical microscope,scanning electron microscope and X-ray diffraction equipment were utilized to study the effects of heating temperature on the microstructure of the joining interface.The compressive strength of the brazed composite grits was also measured.The experimental results show that the atoms of Ti,Al,B and N have preferentially penetrated towards the joining interface of composite grits and filler alloy.The compounds of Ti-nitride,Ti-borides and Ti3AlN were formed in the reaction layer.Degradation effect was not made on the compressive strength of the CBN-AlN composite grits when the brazing process was carried out in the temperature range of 890-920 ℃.展开更多
In this study,Cu/WS_(2) self-lubricating composites are fabricated by spark plasma sintering.Interfacial microstructure and its effect on mechanical and tribological properties are investigated.High sintering temperat...In this study,Cu/WS_(2) self-lubricating composites are fabricated by spark plasma sintering.Interfacial microstructure and its effect on mechanical and tribological properties are investigated.High sintering temperature at 850℃promotes decomposition of WS_(2) and its following interfacial reaction with Cu to form Cu_(0.4)W_(0.6) nanoparticles and Cu_(2)S,enhancing mechanical properties as well as wear resistance of the composites.But the destruction of WS_(2) leads to a high friction coefficient.On the contrary,for the composites sintered at 750℃,a nanoscale diffusion zone forms at the Cu/WS_(2) interface.WS_(2) lubricant retains its lamellar structure.The composite shows excellent self-lubrication performance,with a low friction coefficient of 0.16.However,its mechanical properties are low,and the wear rate is one magnitude higher.展开更多
Effect of a direct magnetic field on the interfacial microstructure between molten aluminium and solid iron was studied. The intermetallic phases formed in the intermetallic layers were investigated by means of electr...Effect of a direct magnetic field on the interfacial microstructure between molten aluminium and solid iron was studied. The intermetallic phases formed in the intermetallic layers were investigated by means of electron probe microanalysis (EPMA) and X-ray diffraction (XRD). It was found that the DC magnetic field can reduce the average thickness of the intermetallic layer and the average aluminium content in the intermetallic layer. Moreover, the intermetallic phases formed in the intermetallic layers are identified as Al3Fe and Al5Fe2 in the absence of the DC magnetic field, while only Al5Fe2 phase present in the presence of the DC magnetic field.展开更多
The interfacial microstructure evolution of 12Cr1MoV/TP347H dissimilar steel welded joints with a nickel-based filler metal during aging was studied in detail to elucidate the mechanism of premature failures of this k...The interfacial microstructure evolution of 12Cr1MoV/TP347H dissimilar steel welded joints with a nickel-based filler metal during aging was studied in detail to elucidate the mechanism of premature failures of this kind of joints.The results showed that not only a band of granular Cr_(23)C_(6)carbides were formed along the fusion boundary in the ferritic steel during aging,but also a large number of granular or plate-like Cr_(23)C_(6)carbides,which have a cube-cube orientation relationship with the matrix,were also precipitated on the weld metal side of the fu-sion boundary,making this zone be etched more easily than the other zone and become a dark etched band.Stacking faults were found in some Cr_(23)C_(6)carbides.In the as-welded state,deformation twins were observed in the weld metal with a fully austenitic structure.The peak micro-hardness was shifted from the ferritic steel side to the weld metal side of the fusion boundary after aging and the peak value increased signific-antly.Based on the experimental results,a mechanism of premature failures of the joints was proposed.展开更多
Joining experiments of CBN grains to AISI 1045 steel were conducted using Ag-Cu-Ti composite fillers containing TiX （X=B2 or N） particles at 920 ℃ for 5 min. The influences of TiB2 and TiN particles on the interfac...Joining experiments of CBN grains to AISI 1045 steel were conducted using Ag-Cu-Ti composite fillers containing TiX （X=B2 or N） particles at 920 ℃ for 5 min. The influences of TiB2 and TiN particles on the interfacial microstructure features between CBN and filler were investigated comparatively. The experimental results show that TiN particles are more effective than TiB2 ones to control the interfacial reaction and particularly the resultants. Thermodynamic analysis reveals that the varied interfacial reaction induced by the addition of TiB2 and TiN particles is mainly atttributed to the activity change of the B and Ti elements in the brazing reaction system.展开更多
A356/6061 bimetallic specimens were prepared by liquid-solid compound casting.The effects of various casting conditions on the interfacial microstructure and mechanical properties of the bimetallic specimens were stud...A356/6061 bimetallic specimens were prepared by liquid-solid compound casting.The effects of various casting conditions on the interfacial microstructure and mechanical properties of the bimetallic specimens were studied.Results demonstrate that a combination of chemical zinc deposition and electroplating can create a dense protective layer on the surface of the 6061 aluminum bar,achieving complete metallurgical bonding at the bimetallic interface.The interfacial microstructure is primarily characterized by equiaxed grain formation,with eutectic silicon distributed along the grain boundaries.Notably,the thickness of the zinc plating layer does not significantly influence the microstructure of the interface transition layer.Pouring temperature is critical for establishing metallurgical bonding at the bimetallic interface,with the thickness of the transition layer increasing as the pouring temperature rises.The hardness of the bimetallic composite interface falls between the hardness values of the two constituent materials.While the thickness of the galvanized layer has a minimal effect on interfacial shear strength,there is a slight decrease in shear strength with increasing pouring temperature,with a maximum value recorded at 68 MPa.展开更多
Interfacial evolution and bonding mechanism of reduced activation ferritic/martensitic(RAFM)steel were systematically investigated through a series of hot compression tests conducted at various strains(0.15-0.8),strai...Interfacial evolution and bonding mechanism of reduced activation ferritic/martensitic(RAFM)steel were systematically investigated through a series of hot compression tests conducted at various strains(0.15-0.8),strain rates(0.001-1 s^(-1)),and temperatures(950-1050℃).Interfacial microstructural analysis revealed that plastic deformation of surface asperities effectively removes interfacial voids,and the evolution of dynamic recrystallization(DRX)aids in achieving a joint characterized by homogeneously refined microstructure and adequate interfacial grain boundary(IGB)migration.Electron backscattered diffraction analysis demonstrated that the continuous dynamic recrystallization,characterized by progressive subgrain rotation,is the prevailing DRX nucleation mechanism in RAFM steel during hot compression bonding.During DRX evolution,emerging DRX grains in the interfacial region expand into adjacent areas,transforming T-type triple junction grain boundaries into equal form,and resulting in a serrated and intricate interface.Elevated temperatures and strains,coupled with reduced strain rates,augment DRX grain nucleation and IGB migration,thus enhancing RAFM joint quality with regard to the interface bonding ratio and the interface migration ratio.展开更多
A novel micro-nano Ti−10Cu−10Ni−8Al−8Nb−4Zr−1.5Hf filler was used to vacuum braze Ti−47Al−2Nb−2Cr−0.15B alloy at 1160−1220℃ for 30 min.The interfacial microstructure and formation mechanism of TiAl joints and the rel...A novel micro-nano Ti−10Cu−10Ni−8Al−8Nb−4Zr−1.5Hf filler was used to vacuum braze Ti−47Al−2Nb−2Cr−0.15B alloy at 1160−1220℃ for 30 min.The interfacial microstructure and formation mechanism of TiAl joints and the relationships among brazing temperature,interfacial microstructure and joint strength were emphatically investigated.Results show that the TiAl joints brazed at 1160 and 1180℃ possess three interfacial layers and mainly consist of α_(2)-Ti_(3)Al,τ_(3)-Al_(3)NiTi_(2) and Ti_(2)Ni,but the brazing seams are no longer layered and Ti_(2)Ni is completely replaced by the uniformly distributed τ_(3)-Al_(3)NiTi_(2) at 1200 and 1220℃ due to the destruction of α_(2)-Ti_(3)Al barrier layer.This transformation at 1200℃ obviously improves the tensile strength of the joint and obtains a maximum of 343 MPa.Notably,the outward diffusion of Al atoms from the dissolution of TiAl substrate dominates the microstructure evolution and tensile strength of the TiAl joint at different brazing temperatures.展开更多
The influence of Mo and ZrO_(2)nanoparticles addition on the interfacial properties and shear strength of Sn58Bi solder joint was investigated.The interfacial microstructures of Sn58Bi/Cu,Sn58Bi+Mo/Cu and Sn58Bi+ZrO_(...The influence of Mo and ZrO_(2)nanoparticles addition on the interfacial properties and shear strength of Sn58Bi solder joint was investigated.The interfacial microstructures of Sn58Bi/Cu,Sn58Bi+Mo/Cu and Sn58Bi+ZrO_(2)/Cu solder joints were analysed using a scanning electron microscope(SEM)coupled with energy dispersive X-ray(EDX)and the X-ray diffraction(XRD).Intermetallic compounds(IMCs)of MoSn_(2)are detected in the Sn58Bi+Mo/Cu solder joint,while SnZr,Zr_(5)Sn_(3),ZrCu and ZrSn_(2)are detected in Sn58Bi+ZrO_(2)/Cu solder joint.IMC layers for both composite solders comprise of Cu_(6)Sn_(5) and Cu_(3)Sn.The SEM images of these layers were used to measure the IMC layer’s thickness.The average IMC layer’s thickness is 1.4431μm for Sn58Bi+Mo/Cu and 0.9112μm for Sn58Bi+ZrO_(2)/Cu solder joints.Shear strength of the solder joints was investigated via the single shear lap test method.The average maximum load and shear stress of the Sn58Bi+Mo/Cu and Sn58Bi+ZrO_(2)/Cu solder joints are increased by 33%and 69%,respectively,as compared to those of the Sn58Bi/Cu solder joint.By comparing both composite solder joints,the latter prevails better as adding smaller sized ZrO_(2)nanoparticles improves the interfacial properties granting a stronger solder joint.展开更多
Reactive brazing of TiAl-based intermetallics and Ni-based alloy with Ti foil as interlayer was investigated. The interfacial microstructure and shear strength of the joints were studied. According to the experimental...Reactive brazing of TiAl-based intermetallics and Ni-based alloy with Ti foil as interlayer was investigated. The interfacial microstructure and shear strength of the joints were studied. According to the experimental observations, the molten interlayer reacts vigorously with base metals, forming several continuous reaction layers. The typical interfacial microstructure of the joint can be expressed as GH99/（Ni,Cr）ss（γ）/TiNi（β2）＋TiNi2Al（τ4）＋Ti2Ni（δ）/δ＋Ti3Al（α2）＋Al3NiTi2（τ3）/α2＋τ3/TiAl. The maximum shear strength is 258 MPa for the specimen brazed at 1000°C for 10 min. Higher brazing temperature or longer brazing time causes coarsening of the phases in the brazing seam and formation of brittle intermetallic layer, which greatly depresses the shear strength of the joints.展开更多
The investigation evaluated the thermal shock resistance and failure mechanisms of three brazed joints when exposed to 780°C.During exposure,oxidation of the SiC_(f)/SiC composite leads to the formation of SiO_(2...The investigation evaluated the thermal shock resistance and failure mechanisms of three brazed joints when exposed to 780°C.During exposure,oxidation of the SiC_(f)/SiC composite leads to the formation of SiO_(2).Residual oxygen will penetrate the high-entropy alloy while retaining its Face-Centered Cubic(FCC)structure.Additionally,the FCC Cr_(23)C_(6)phase adjacent to the composite reacted with SiC,producing hexagonal Cr_(2)C,compromising the ability of joint to withstand plastic deformation.Moreover,the presence of Nb(s,s)and significant MoNiSi phases induced a gradual alteration in the Coefficient of Thermal Expansion(CTE),facilitating the initiation of shear fractures from the composites towards the central region of the seam,significantly affecting the overall structural integrity and failure behavior of the joint under thermal shock conditions.With an increase in the number of thermal shocks,the shear strength of joint gradually decreases,reaching a maximum of 22.36 MPa after 30 thermal shocks,surpassing that of some joints using glass fillers.展开更多
Friction stir lap welding(FSLW)was adopted to join successfully dissimilar AZ31B Mg alloy and TC4 Ti alloy with Sn foil addition of 30μm thickness.Interfacial microstructure,tensile shear performances and bonding mec...Friction stir lap welding(FSLW)was adopted to join successfully dissimilar AZ31B Mg alloy and TC4 Ti alloy with Sn foil addition of 30μm thickness.Interfacial microstructure,tensile shear performances and bonding mechanism of the joints obtained using three different rotation speeds were studied.High-performance FSLW Mg/Ti dissimilar joints with maximum tensile shear strength of 593.3 N/mm were produced at 1180 r/min,and which was mainly attributed to ultrastrong reaction interlayer consisting of 125.9 nm thick(Mg_(2)Sn+Mg)transition layer and discontinuous(Ti_(6)Sn_(5)+Ti_(3)Al)IMCs layer with 6.58 nm thickness at the interface.The formation of the reaction interlayer was beneficial for high interfacial strength,resulting in significantly improving the joint strength.The fracture of all FSLW joints located on AZ31B Mg stirred zone adjacent to(Mg_(2)Sn+Mg)transition layer or along the crack propagation direction of the AZ31B/TC4 interface with different fracture mechanisms,and which could be consistent with interfacial microstructure.展开更多
Ti-coated SiCp particles were developed by vacuum evaporation with Ti to improve the interfacial bonding of SiCp/Al composites.Ti-coated SiC particles and uncoated SiC particles reinforced Al 2519 matrix composites we...Ti-coated SiCp particles were developed by vacuum evaporation with Ti to improve the interfacial bonding of SiCp/Al composites.Ti-coated SiC particles and uncoated SiC particles reinforced Al 2519 matrix composites were prepared by hot pressing,hot extrusion and heat treatment.The influence of Ti coating on microstructure and mechanical properties of the composites was analyzed by scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS).The results show that the densely deposited Ti coating reacts with SiC particles to form TiC and Ti5Si3 phases at the interface.Ti-coated SiC particle reinforced composite exhibits uniformity and compactness compared to the composite reinforced with uncoated SiC particles.The microstructure,relative density and mechanical properties of the composite are significantly improved.When the volume fraction is 15%,the hardness,fracture strain and tensile strength of the SiCp reinforced Al 2519 composite after Ti plating are optimized,which are HB 138.5,4.02%and 455 MPa,respectively.展开更多
Ti/Al/Mg laminated composites were successfully fabricated by hot roll bonding.The effects of the rolling reduction on the microstructural evolution and mechanical properties of the composites were explored.The result...Ti/Al/Mg laminated composites were successfully fabricated by hot roll bonding.The effects of the rolling reduction on the microstructural evolution and mechanical properties of the composites were explored.The results show that Ti/Al/Mg laminated sheets exhibit good interfacial bonding.The rolling reduction has a significant effect on the deformation inhomogeneity through the thickness of the Al layer.The initial grains of the Al layer near the Ti/Al interface are fragmented into fine equiaxed grains,and the grains at the center and near the Al/Mg interface are elongated.The R-cube shear texture of the Al layer forms near the Ti/Al interface and permeates into the center layer in the samples with greater rolling reductions.The b-fiber rolling texture of the Al layer is observed near the Al/Mg interface and increases with the increase of rolling reduction.The stress–strain curves indicate that the fracture appears first in the Mg layer.With the increasing rolling reduction,the ultimate tensile and yield strength values increase,and the elongation up to the Mg layer fracture decreases.展开更多
Ti/Cu/Ti laminated composites were fabricated by corrugated rolling(CR) and flat rolling(FR) method.Microstructure and mechanical properties of CR and FR laminated composites were investigated by scanning electron mic...Ti/Cu/Ti laminated composites were fabricated by corrugated rolling(CR) and flat rolling(FR) method.Microstructure and mechanical properties of CR and FR laminated composites were investigated by scanning electron microscopy, numerical simulation methods, peel and tensile examinations. The effect of CR and FR was comparatively analyzed. The results showed that the CR and FR laminated composites exhibited different effective plastic strain distributions of the Ti layer and Cu layer at the interface. The recrystallization texture, prismatic texture and pyramidal texture were developed in the Ti layer by CR, while the R-Goss texture and shear texture were developed in the Cu layer by CR. The typical deformation texture components were developed in the Ti layer and Cu layer of FR laminated composites. The CR laminated composites had higher bond strength, tensile strength and ductility.展开更多
The welding of aluminum(Al)and steel has attracted more and more interest due to the weight reduction trend in vehicle and aerospace manufacturing industries.5182-O/HC260YD+Z lap joint was produced by friction stir we...The welding of aluminum(Al)and steel has attracted more and more interest due to the weight reduction trend in vehicle and aerospace manufacturing industries.5182-O/HC260YD+Z lap joint was produced by friction stir welding(FSW),and the microstructure and mechanical property of the joint were systemically characterized.The microstructure in horizontal direction of the Al and steel near interface was similar to their corresponding conventional friction stir welded joint.The joint was divided into stir zone of Al(ST-Al),stir zone of interface(ST-I),thermal-mechanically affected zone of steel(TMAZ-Fe)and base material of steel(BM-Fe)according to their distinct microstructure vertically.Three kinds of intermetallic compounds(IMCs)of FeAl_(3),FeAl and Fe_(3)Al were formed at the interface.The horizontal micro hardness distribution exhibited a hat shape and“M”shape in Al and steel,respectively.The hardest region of the joint was located at the ST-I,with a hardness of 175 HV−210 HV.The joint was fractured along the hook structure,with an average shear strength of 73.9 MPa.Fractural morphology of Al and steel indicted a cleavage fracture mode.展开更多
基金funded by the National Natural Science Foundation of China(Nos.52271102,52075198 and 52205359)。
文摘In this work,a new treatment method combining ultrasonic vibration with FeCoNiCrCu high entropy alloy(HEA)coating was used to prepared Al/Mg bimetal through the lost foam compound casting.The effects of composite treatment involving ultrasonic vibration and HEA coating on interfacial microstructure and mechanical properties of Al/Mg bimetal were studied.Results demonstrate that the interface thickness of the Al/Mg bimetal with composite treatment significantly decreases to only 26.99%of the thickness observed in the untreated Al/Mg bimetal.The HEA coating hinders the diffusion between Al and Mg,resulting the significant reduction in Al/Mg intermetallic compounds in the interface.The Al/Mg bimetal interface with composite treatment is composed of Al_(3)Mg_(2)and Mg_(2)Si/AlxFeCoNiCrCu+FeCoNiCrCu/δ-Mg+Al_(12)Mg_(17)eutectic structures.The interface resulting from the composite treatment has a lower hardness than that without treatment.The acoustic cavitation and acoustic streaming effects generated by ultrasonic vibration promote the diffusion of Al elements within the HEA coating,resulting in a significant improvement in the metallurgical bonding quality on the Mg side.The fracture position shifts from the Mg side of the Al/Mg bimetal only with HEA coating to the Al side with composite treatment.The shear strength of the Al/Mg bimetal increases from 32.16 MPa without treatment to 63.44 MPa with ultrasonic vibration and HEA coating,increasing by 97.26%.
基金Project(51671017)supported by the National Natural Science Foundation of ChinaProject(FRF-GF-17-B3)supported by the Fundamental Research Funds for the Central Universities,China+1 种基金Project supported by the Beijing Laboratory of Metallic Materials and Processing for Modern Transportation,ChinaProject(SKLSP201835)supported by the Fund of the State Key Laboratory of Solidification Processing in NWPU,China
文摘Mg/Cu bimetal composites were prepared by compound casting method, and the microstructure evolution, phase constitution and bonding strength at the interface were investigated.It is found that a good metallurgical bonding can be achieved at the interface of Mg and Cu,which consists of two sub-layers,i.e.,layer I with 30μm on the copper side composed of Mg2Cu matrix phase, on which a small amount of dendritic MgCu2 phase was randomly distributed;layerⅡ with 140μm on the magnesium side made up of the lamellar nano-eutectic network Mg2Cu+(Mg) and a small amount of detached Mg2Cu phase. The average interfacial shear strength of the bimetal composite is measured to be 13 MPa.This study provides a new fabrication process for the application of Mg/Cu bimetal composites as the hydrogen storage materials.
基金the supports provided by the National Natural Science Foundation of China(No.52075198)the National Key Research and Development Program of China(Nos.2020YFB2008300,2020YFB2008304)+1 种基金the State Key Lab of Advanced Metals and Materials(No.2021-ZD07)the Analytical and Testing Center,HUST。
文摘In this work,a vibration was applied in the preparation of the Mg/Al bimetal by a novel compound casting in order to improve the mechanical properties of the Mg/Al bimetal,and the effect of the vibration on the interfacial microstructure and mechanical properties of the Mg/Al bimetal was investigated.The results indicated that the vibration had a significant effect on the interfacial microstructure and mechanical properties of the Mg/Al bimetal,but it did not change the phase compositions of the interface,which was composed of layerⅠ(Al3Mg2+Mg2Si),layerⅡ(Al_(12)Mg_(17)+Mg_(2)Si)and layerⅢ(Al_(12)Mg_(17)/δ-Mg).Without vibration,the Mg_(2)Si phase with a needle-like morphology mainly aggregated in the layerⅡof the interface.After the application of the vibration,the SEM and EBSD analysis results showed that the Mg_(2)Si and Al3Mg2phases in the interface were obviously refined,and the distribution of the Mg_(2)Si became more uniform,due to the strong forced convection of the molten metal resulting from the vibration.The TEM analysis indicated that the interface between the A_(l3)Mg_(2) and Mg_(2)Si phases was non-coherent,suggesting the Mg_(2)Si particles cannot act as a heterogeneous nucleation base during the solidification process of the interface.Compared to the Mg/Al bimetal without vibration,the shear strength of the Mg/Al bimetal with vibration increased by about 50%from 31.7 MPa on average to 47.5 MPa,and the hardness of the layer I of the interface increased,and the hardness of the layerⅢdecreased.The fracture surface transformed from a flat fracture morphology without vibration to an irregular zigzag fracture morphology.
基金Project(51435004)supported by the National Natural Science Foundation of China
文摘Soldering aluminum alloys at low temperature have great potential to avoid softening of base metals.Pure Al was solderedwith pure tin assisted by ultrasound.The influence of primaryα(Al)on the microstructure of Al/Sn interface and its bonding strengthwas studied.It is found that the primaryα(Al)in liquid tin tends to be octahedron enclosed by Al{111}facet with the lowest surfacefree energy and growth rate.The ultrasonic action could increase the nucleation rate and refine the particles of primaryα(Al).For thelonger ultrasonic and holding time,a large amount of the octahedral primaryα(Al)particles crystallize at the Al/Sn interface.Thebonding interface exhibits the profile of rough dentation,resulting in an increment of bonding interface area and the effect ofmechanical occlusion.The bonding strength at interface could reach63MPa with ultrasonic time of40s and holding time of10min.
基金Funded by the National Basic Research Program of China (No.2009CB724403)the National Natural Science Foundation of China (No.51005116)+1 种基金the Program for Changjiang Scholars and Innovative Research Team in University (No. IRT0837)the NUAA Research Funding (No. 2010236)
文摘CBN-AlN composite abrasive grits and AISI 1045 steel were brazed using Ag-Cu-Ti active filler alloy by heating up to the temperature of 890,900 and 920 ℃,respectively,and then held at the temperature for 8 min.Optical microscope,scanning electron microscope and X-ray diffraction equipment were utilized to study the effects of heating temperature on the microstructure of the joining interface.The compressive strength of the brazed composite grits was also measured.The experimental results show that the atoms of Ti,Al,B and N have preferentially penetrated towards the joining interface of composite grits and filler alloy.The compounds of Ti-nitride,Ti-borides and Ti3AlN were formed in the reaction layer.Degradation effect was not made on the compressive strength of the CBN-AlN composite grits when the brazing process was carried out in the temperature range of 890-920 ℃.
基金financially supported by the Fundamental Research Funds for the Central Universities(Nos.N180212008 and N181003001)the National Natural Science Foundation of China(No.51701224)the Ministry of Industry and Information Technology Project(No.MJ-2017-J-99)。
文摘In this study,Cu/WS_(2) self-lubricating composites are fabricated by spark plasma sintering.Interfacial microstructure and its effect on mechanical and tribological properties are investigated.High sintering temperature at 850℃promotes decomposition of WS_(2) and its following interfacial reaction with Cu to form Cu_(0.4)W_(0.6) nanoparticles and Cu_(2)S,enhancing mechanical properties as well as wear resistance of the composites.But the destruction of WS_(2) leads to a high friction coefficient.On the contrary,for the composites sintered at 750℃,a nanoscale diffusion zone forms at the Cu/WS_(2) interface.WS_(2) lubricant retains its lamellar structure.The composite shows excellent self-lubrication performance,with a low friction coefficient of 0.16.However,its mechanical properties are low,and the wear rate is one magnitude higher.
基金The paper is supported by National Key Basic Research Pro-gram (973) under grant No. 2005CB623707.
文摘Effect of a direct magnetic field on the interfacial microstructure between molten aluminium and solid iron was studied. The intermetallic phases formed in the intermetallic layers were investigated by means of electron probe microanalysis (EPMA) and X-ray diffraction (XRD). It was found that the DC magnetic field can reduce the average thickness of the intermetallic layer and the average aluminium content in the intermetallic layer. Moreover, the intermetallic phases formed in the intermetallic layers are identified as Al3Fe and Al5Fe2 in the absence of the DC magnetic field, while only Al5Fe2 phase present in the presence of the DC magnetic field.
文摘The interfacial microstructure evolution of 12Cr1MoV/TP347H dissimilar steel welded joints with a nickel-based filler metal during aging was studied in detail to elucidate the mechanism of premature failures of this kind of joints.The results showed that not only a band of granular Cr_(23)C_(6)carbides were formed along the fusion boundary in the ferritic steel during aging,but also a large number of granular or plate-like Cr_(23)C_(6)carbides,which have a cube-cube orientation relationship with the matrix,were also precipitated on the weld metal side of the fu-sion boundary,making this zone be etched more easily than the other zone and become a dark etched band.Stacking faults were found in some Cr_(23)C_(6)carbides.In the as-welded state,deformation twins were observed in the weld metal with a fully austenitic structure.The peak micro-hardness was shifted from the ferritic steel side to the weld metal side of the fusion boundary after aging and the peak value increased signific-antly.Based on the experimental results,a mechanism of premature failures of the joints was proposed.
基金Funded by the National Fundamental Research Program of China (No.2009CB724403)Program for New Century Excellent Talents in University from Ministry of Education of China (No. NCET-07-0435)
文摘Joining experiments of CBN grains to AISI 1045 steel were conducted using Ag-Cu-Ti composite fillers containing TiX （X=B2 or N） particles at 920 ℃ for 5 min. The influences of TiB2 and TiN particles on the interfacial microstructure features between CBN and filler were investigated comparatively. The experimental results show that TiN particles are more effective than TiB2 ones to control the interfacial reaction and particularly the resultants. Thermodynamic analysis reveals that the varied interfacial reaction induced by the addition of TiB2 and TiN particles is mainly atttributed to the activity change of the B and Ti elements in the brazing reaction system.
基金financially supported by the National Natural Science Foundation of China(Grant No.52275370)the Key R&D Program of Hubei Province,China(Grant No.2024BAB072)the Research Fund of the State Key Laboratory of Intelligent Agricultural Power Equipment(Grant No.SKLIAPE2023014).
文摘A356/6061 bimetallic specimens were prepared by liquid-solid compound casting.The effects of various casting conditions on the interfacial microstructure and mechanical properties of the bimetallic specimens were studied.Results demonstrate that a combination of chemical zinc deposition and electroplating can create a dense protective layer on the surface of the 6061 aluminum bar,achieving complete metallurgical bonding at the bimetallic interface.The interfacial microstructure is primarily characterized by equiaxed grain formation,with eutectic silicon distributed along the grain boundaries.Notably,the thickness of the zinc plating layer does not significantly influence the microstructure of the interface transition layer.Pouring temperature is critical for establishing metallurgical bonding at the bimetallic interface,with the thickness of the transition layer increasing as the pouring temperature rises.The hardness of the bimetallic composite interface falls between the hardness values of the two constituent materials.While the thickness of the galvanized layer has a minimal effect on interfacial shear strength,there is a slight decrease in shear strength with increasing pouring temperature,with a maximum value recorded at 68 MPa.
基金The authors are grateful to the National Natural Science Foundation of China(Grant Nos.52034004 and 52271111)the National Key R&D Program of China(2022YFB3705300)for grant and financial support.
文摘Interfacial evolution and bonding mechanism of reduced activation ferritic/martensitic(RAFM)steel were systematically investigated through a series of hot compression tests conducted at various strains(0.15-0.8),strain rates(0.001-1 s^(-1)),and temperatures(950-1050℃).Interfacial microstructural analysis revealed that plastic deformation of surface asperities effectively removes interfacial voids,and the evolution of dynamic recrystallization(DRX)aids in achieving a joint characterized by homogeneously refined microstructure and adequate interfacial grain boundary(IGB)migration.Electron backscattered diffraction analysis demonstrated that the continuous dynamic recrystallization,characterized by progressive subgrain rotation,is the prevailing DRX nucleation mechanism in RAFM steel during hot compression bonding.During DRX evolution,emerging DRX grains in the interfacial region expand into adjacent areas,transforming T-type triple junction grain boundaries into equal form,and resulting in a serrated and intricate interface.Elevated temperatures and strains,coupled with reduced strain rates,augment DRX grain nucleation and IGB migration,thus enhancing RAFM joint quality with regard to the interface bonding ratio and the interface migration ratio.
基金the National Natural Science Foundation of China(No.51865012)the Natural Science Foundation of Jiangxi Province,China(No.20202BABL204040)+3 种基金the Open Foundation of National Engineering Research Center of Near-net-shape Forming for Metallic Materials,China(No.2016005)the Science Foundation of Educational Department of Jiangxi Province,China(No.GJJ170372)the GF Basic Scientific Research Project,China(No.JCKY2020205C002)the Civil Population Supporting Planning and Development Project,China(No.JPPT125GH038).
文摘A novel micro-nano Ti−10Cu−10Ni−8Al−8Nb−4Zr−1.5Hf filler was used to vacuum braze Ti−47Al−2Nb−2Cr−0.15B alloy at 1160−1220℃ for 30 min.The interfacial microstructure and formation mechanism of TiAl joints and the relationships among brazing temperature,interfacial microstructure and joint strength were emphatically investigated.Results show that the TiAl joints brazed at 1160 and 1180℃ possess three interfacial layers and mainly consist of α_(2)-Ti_(3)Al,τ_(3)-Al_(3)NiTi_(2) and Ti_(2)Ni,but the brazing seams are no longer layered and Ti_(2)Ni is completely replaced by the uniformly distributed τ_(3)-Al_(3)NiTi_(2) at 1200 and 1220℃ due to the destruction of α_(2)-Ti_(3)Al barrier layer.This transformation at 1200℃ obviously improves the tensile strength of the joint and obtains a maximum of 343 MPa.Notably,the outward diffusion of Al atoms from the dissolution of TiAl substrate dominates the microstructure evolution and tensile strength of the TiAl joint at different brazing temperatures.
文摘The influence of Mo and ZrO_(2)nanoparticles addition on the interfacial properties and shear strength of Sn58Bi solder joint was investigated.The interfacial microstructures of Sn58Bi/Cu,Sn58Bi+Mo/Cu and Sn58Bi+ZrO_(2)/Cu solder joints were analysed using a scanning electron microscope(SEM)coupled with energy dispersive X-ray(EDX)and the X-ray diffraction(XRD).Intermetallic compounds(IMCs)of MoSn_(2)are detected in the Sn58Bi+Mo/Cu solder joint,while SnZr,Zr_(5)Sn_(3),ZrCu and ZrSn_(2)are detected in Sn58Bi+ZrO_(2)/Cu solder joint.IMC layers for both composite solders comprise of Cu_(6)Sn_(5) and Cu_(3)Sn.The SEM images of these layers were used to measure the IMC layer’s thickness.The average IMC layer’s thickness is 1.4431μm for Sn58Bi+Mo/Cu and 0.9112μm for Sn58Bi+ZrO_(2)/Cu solder joints.Shear strength of the solder joints was investigated via the single shear lap test method.The average maximum load and shear stress of the Sn58Bi+Mo/Cu and Sn58Bi+ZrO_(2)/Cu solder joints are increased by 33%and 69%,respectively,as compared to those of the Sn58Bi/Cu solder joint.By comparing both composite solder joints,the latter prevails better as adding smaller sized ZrO_(2)nanoparticles improves the interfacial properties granting a stronger solder joint.
基金Projects (50975062, 51105107, 51021002) supported by the National Natural Science Foundation of ChinaProjects (QC2011C044) supported by the Natural Science Foundation of Heilongjiang Province,China+1 种基金Project (20112302130005) supported by the Specialized Research Fund for the Doctoral Program of Higher Education,ChinaProject (CUGA4130902510) supported by the China Postdoctoral Science Foundation Funded
文摘Reactive brazing of TiAl-based intermetallics and Ni-based alloy with Ti foil as interlayer was investigated. The interfacial microstructure and shear strength of the joints were studied. According to the experimental observations, the molten interlayer reacts vigorously with base metals, forming several continuous reaction layers. The typical interfacial microstructure of the joint can be expressed as GH99/（Ni,Cr）ss（γ）/TiNi（β2）＋TiNi2Al（τ4）＋Ti2Ni（δ）/δ＋Ti3Al（α2）＋Al3NiTi2（τ3）/α2＋τ3/TiAl. The maximum shear strength is 258 MPa for the specimen brazed at 1000°C for 10 min. Higher brazing temperature or longer brazing time causes coarsening of the phases in the brazing seam and formation of brittle intermetallic layer, which greatly depresses the shear strength of the joints.
基金the financial support from the National Natural Science Foundation of China(No.52374402)the National Key Research and Development Program,China(No.2022YFB3402200)+2 种基金the National Science and Technology Major Project,China(No.J2022-VII-00030045)the Project of Key Areas of Innovation Team in Shaanxi Province,China(No.2024RS-CXTD-20)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University,China(No.CX2024055)。
文摘The investigation evaluated the thermal shock resistance and failure mechanisms of three brazed joints when exposed to 780°C.During exposure,oxidation of the SiC_(f)/SiC composite leads to the formation of SiO_(2).Residual oxygen will penetrate the high-entropy alloy while retaining its Face-Centered Cubic(FCC)structure.Additionally,the FCC Cr_(23)C_(6)phase adjacent to the composite reacted with SiC,producing hexagonal Cr_(2)C,compromising the ability of joint to withstand plastic deformation.Moreover,the presence of Nb(s,s)and significant MoNiSi phases induced a gradual alteration in the Coefficient of Thermal Expansion(CTE),facilitating the initiation of shear fractures from the composites towards the central region of the seam,significantly affecting the overall structural integrity and failure behavior of the joint under thermal shock conditions.With an increase in the number of thermal shocks,the shear strength of joint gradually decreases,reaching a maximum of 22.36 MPa after 30 thermal shocks,surpassing that of some joints using glass fillers.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.52005240,52164045)Young Talent Program of Major Disciplines of Academic and Technical Leaders in Jiangxi Province(No.20212BCJ23028)Outstanding Youth Foundation in Jiangxi Province(No.20224ACB214012).
文摘Friction stir lap welding(FSLW)was adopted to join successfully dissimilar AZ31B Mg alloy and TC4 Ti alloy with Sn foil addition of 30μm thickness.Interfacial microstructure,tensile shear performances and bonding mechanism of the joints obtained using three different rotation speeds were studied.High-performance FSLW Mg/Ti dissimilar joints with maximum tensile shear strength of 593.3 N/mm were produced at 1180 r/min,and which was mainly attributed to ultrastrong reaction interlayer consisting of 125.9 nm thick(Mg_(2)Sn+Mg)transition layer and discontinuous(Ti_(6)Sn_(5)+Ti_(3)Al)IMCs layer with 6.58 nm thickness at the interface.The formation of the reaction interlayer was beneficial for high interfacial strength,resulting in significantly improving the joint strength.The fracture of all FSLW joints located on AZ31B Mg stirred zone adjacent to(Mg_(2)Sn+Mg)transition layer or along the crack propagation direction of the AZ31B/TC4 interface with different fracture mechanisms,and which could be consistent with interfacial microstructure.
基金Project(CXZZ20140506150310438)supported by the Science and Technology Program of Shenzhen,ChinaProject(2017GK2261)supported by the Science and Technology Program of Hunan Province,ChinaProject(2017zzts111)supported by the Fundamental Research Funds for the Central Universities of Central South University,China。
文摘Ti-coated SiCp particles were developed by vacuum evaporation with Ti to improve the interfacial bonding of SiCp/Al composites.Ti-coated SiC particles and uncoated SiC particles reinforced Al 2519 matrix composites were prepared by hot pressing,hot extrusion and heat treatment.The influence of Ti coating on microstructure and mechanical properties of the composites was analyzed by scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS).The results show that the densely deposited Ti coating reacts with SiC particles to form TiC and Ti5Si3 phases at the interface.Ti-coated SiC particle reinforced composite exhibits uniformity and compactness compared to the composite reinforced with uncoated SiC particles.The microstructure,relative density and mechanical properties of the composite are significantly improved.When the volume fraction is 15%,the hardness,fracture strain and tensile strength of the SiCp reinforced Al 2519 composite after Ti plating are optimized,which are HB 138.5,4.02%and 455 MPa,respectively.
基金financial supports from the National Natural Science Foundation of China(No.51421001)the National High Technology Research and Development Program of China(863 Program,No.2013AA031304)+1 种基金the Fundamental Research Funds for the CentralUniversitiesofChina(2019CDQYCL001,2019CDCGCL204,2020CDJDPT001)the Research Project of State Key Laboratory of Vehicle NVH and Safety Technology of China(No.NVHSKL-201706)。
文摘Ti/Al/Mg laminated composites were successfully fabricated by hot roll bonding.The effects of the rolling reduction on the microstructural evolution and mechanical properties of the composites were explored.The results show that Ti/Al/Mg laminated sheets exhibit good interfacial bonding.The rolling reduction has a significant effect on the deformation inhomogeneity through the thickness of the Al layer.The initial grains of the Al layer near the Ti/Al interface are fragmented into fine equiaxed grains,and the grains at the center and near the Al/Mg interface are elongated.The R-cube shear texture of the Al layer forms near the Ti/Al interface and permeates into the center layer in the samples with greater rolling reductions.The b-fiber rolling texture of the Al layer is observed near the Al/Mg interface and increases with the increase of rolling reduction.The stress–strain curves indicate that the fracture appears first in the Mg layer.With the increasing rolling reduction,the ultimate tensile and yield strength values increase,and the elongation up to the Mg layer fracture decreases.
基金financially supported by the National Key R&D Program of China (No.2018YFA0707300)the Natural Science Foundation of Shanxi Province,China (No.201801D221131)+2 种基金the National Natural Science Foundation of China (Nos.51905372,51904206,51805359,52075359)Shanxi Province Science and Technology Major Project,China (No.20181102011)China Postdoctoral Science Foundation (No.2020M670705)。
文摘Ti/Cu/Ti laminated composites were fabricated by corrugated rolling(CR) and flat rolling(FR) method.Microstructure and mechanical properties of CR and FR laminated composites were investigated by scanning electron microscopy, numerical simulation methods, peel and tensile examinations. The effect of CR and FR was comparatively analyzed. The results showed that the CR and FR laminated composites exhibited different effective plastic strain distributions of the Ti layer and Cu layer at the interface. The recrystallization texture, prismatic texture and pyramidal texture were developed in the Ti layer by CR, while the R-Goss texture and shear texture were developed in the Cu layer by CR. The typical deformation texture components were developed in the Ti layer and Cu layer of FR laminated composites. The CR laminated composites had higher bond strength, tensile strength and ductility.
文摘The welding of aluminum(Al)and steel has attracted more and more interest due to the weight reduction trend in vehicle and aerospace manufacturing industries.5182-O/HC260YD+Z lap joint was produced by friction stir welding(FSW),and the microstructure and mechanical property of the joint were systemically characterized.The microstructure in horizontal direction of the Al and steel near interface was similar to their corresponding conventional friction stir welded joint.The joint was divided into stir zone of Al(ST-Al),stir zone of interface(ST-I),thermal-mechanically affected zone of steel(TMAZ-Fe)and base material of steel(BM-Fe)according to their distinct microstructure vertically.Three kinds of intermetallic compounds(IMCs)of FeAl_(3),FeAl and Fe_(3)Al were formed at the interface.The horizontal micro hardness distribution exhibited a hat shape and“M”shape in Al and steel,respectively.The hardest region of the joint was located at the ST-I,with a hardness of 175 HV−210 HV.The joint was fractured along the hook structure,with an average shear strength of 73.9 MPa.Fractural morphology of Al and steel indicted a cleavage fracture mode.
