Abstract:The cold-rolled bonding process of copper/aluminum bimetal plate was investigated by the velocity field of FEM. At the same time, deformation characteristics of metal were analyzed in the bonding process. The study method was to combine theory calculation with field data. In the research, the circumferential velocity of rollers, rolling reduction rate, synchronous rolling of non-equal sized rollers and asymmetrical rolling of non-equal sized rollers were analyzed. Studies has shown that the velocity field can explain the cold-rolled bonding process of copper/aluminum bimetal plate more effectively; the synchronicity of metal flow on bonding surface decreases with the increase of circumferential velocity about rollers near the exit of deformation area, and the bonding strength is reduced; the increase of rolling reduction rate is conducive to the synchronicity of metal flow on bonding surface near the exit of deformation area, and the bonding strength is increased; in the process of synchronous rolling about non-equal sized rollers, diameter ratio of the rolls is 1.4~1.6 with a great synchronicity of metal flow near the exit of deformation area and a high bonding strength; in the process of asymmetrical rolling about non-equal sized rollers, the circumferential velocity rate of rollers is 1.2 with a great synchronicity of metal flow near the exit of deformation area and a high bonding strength.

Abstract:The electrochemical behaviors of iridium electrodeposited in 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid were studied. Cyclic voltammograms prepared on the gold electrode suggested that Ir(III) was reduced to iridium with an irreversible one-step process, which was controlled by the diffusion of Ir(III). The diffusion rate is 3.83×10_?11 m₂/s and the average transfer coefficient is 0.083. The morphology and composition of iridium coatings prepared on molybdenum substrates were characterized by scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The morphology of iridium coatings was dependent on the potential, time and current density of electrodeposition. Compact coatings were obtained at the reduction peak potential with a balance between the nucleation rate and the growth rate. Flat and compact coatings were formed when current density ranged from 0.5 to 1.82 mA/cm₂ in the galvanostatic electrodeposition.

Abstract:TiSiCN, TiSiCON, TiCrSiCN, TiCrSiCON, CrSiCN and CrSiCON coatings have been deposited on WC-Co substrates and Si wafers using plasma enhanced magnetron sputtering (PEMS) technique. The microstructure, composition and mechanical properties of the non-oxygen coatings and oxygen-containing coatings were studied by using XRD, SEM, EDS and load-depth-sensing indentation. The tribological behavior of the coatings against Al2O3 balls was conducted by pin-on-disc tests. The results showed that TiSiCON, TiCrSiCON and CrSiCON coatings exhibited the face center cubic (fcc) TiN-type (or CrN-type) structure but the existence of oxygen will induce loose structure and more defects for TiSiCON, TiCrSiCON and CrSiCON coatings compared with TiSiCN，TiCrSiCN and CrSiCN, respectively. The addition of oxygen element would lead to the decrease of the hardness (H) and elasticity of Ti(Cr)SiCN coatings. TiCrSiCON and CrSiCON coatings with oxygen element have lower friction coefficients and wear rate compared with TiCrSiCN and CrSiCN coatings without oxygen, respectively. While the TiSiCON with higher friction coefficient and wear rate shows poor abrasive wear resistance than TiSiCN.

Abstract:This paper investigated the effect of aging treatment before extrusion on microstructure and mechanical properties of AZ80 magnesium alloy. Fractural microstructures of the test specimens were also analyzed by scanning electron microscopy. Results show that aging treatment before extrusion can remarkably promote grain refinement; the dispersed Mg₁₇Al₁₂ particles that precipitated from the matrix during aging treatment before extrusion distribute in the grain boundaries, during the subsequent extrusion process these particles can pin grain boundaries migration and lead to fine microstructure; however, with prolonging the aging time, the grain refinement effect was weakened. After aging treatment and subsequent extrusion, the yield strength, tensile strength and elongation are increased. Based on fracture surface analyzed, the premature cracks generate around big particles that present in grain boundaries lead to loss of elongation. The strengthening effect of aging before extrusion in AZ80 magnesium alloy proven in this paper provides a new method for the design of the relatively high-performance magnesium alloys.

Abstract:The influence of mischmetal (lanthanum and cerium) on the microstructure and mechanical properties of Mg-9Li-3Al-xRE (x=0, 0.5, 1, 1.5 and 2 wt.%) alloys was investigated. In as-cast alloys, Al4RE phase was formed, the content of Mg17Al12 phase and the volume fraction of α-Mg phase were decreased. In addition, α-Mg phase was refined and the mechanical properties of Mg-9Li-3Al-xRE alloys were improved. However, with increasing mischmetal content, the size of Al4RE phase increases and the mechanical properties decrease. In extruded alloys, the Al4RE phase was broken into the particles of ~1-3μm in the β-Li matrix phase and α/β interphase. And the best mechanical properties was obtained for Mg-9Li-3Al-1.5RE alloy with a tensile strength of 228.3MPa and elongation of 20.8%, increased by 88.6% and 197.4%, respectively, compared with as-cast Mg-9Li-3Al alloy.

Abstract:Effect of annealing temperature (θa) on the transformation and the low temperature deformation characteristics in the deformed Ti-51.1Ni (Atomic fraction, %) shape memory alloy (SMA) are investigated by differential scanning calorimetry (DSC) and tensile test. The results shows that the transformation types of Ti-51.1Ni alloy change from A→R / M→R→A to A→R→M / M→R→A to A→R→M / M→A ( A-parent phase B2, R-R phase, M-martensite phase) upon cooling / heating along with increasing annealing temperature,. The R transformation temperatures (θ_R) and martensite (M) temperature hysteresis (_?θ_M) decrease, the M transformation temperature increases, and the R temperature hysteresis (_?θ_R) does not nearly change as about 6.5℃. When deformed at 10 ℃, the 400-550 ℃ annealed Ti-51.1Ni SMA shows shape memory effect (SME) + superelasticity (SE), the 600-700 ℃ annealed Ti-51.1Ni SMA shows SE, and the characteristics of alloy change from SME SE to SE. In addition, the annealing recrystallization temperature of Ti-51.1Ni SMA were 590 ℃, and the 590-650 ℃ annealed alloy could be obtained excellent capability of plastic deformation and 50.83 %Svalues of fractureSstrain, so the molding processing temperature could be selected at 590~650 ℃. When the Ti-51.1Ni alloy are used for production energy consumption ofSdamper and damping device, the suitable annealing temperature could be selected at more than 550℃, and making of superelasticSdevice, the suitable annealing temperature could be selected at 400 ℃ less and 600 ℃ more.

Abstract:FePd alloy films with different thickness have been prepared by DC magnetron sputtering on glass. The effect of thin film thickness on the structural and magnetic properties was investigated. The results indicate that the ordering process in the thin FePd alloy film occurs in the thicker ones. In-plane coercivity value first increases rapidly as thickness increases from d=22.5 to 67.5 nm, and then the value decreases with further increasing film thickness. A peak value of coercivity～3200Oe appears at d=67.5 nm.

Abstract:In the paper Laser Additive Manufacturing (LAM) has been employed to fabricate repaired samples with wrought Ti6Al4V as the substrate and Ti6Al4V (Ti64) powders with low oxygen (O≤0.13wt%) as the cladding materials. The microstructure and mechanical properties of Ti64 samples fabricated by LAM and wrought billet were investigated comparatively. The results show that the macrostructure of the laser repaired sample can be divided into three domains, including wrought substrate zone (SZ), heat affected zone (HAZ) and laser deposited zone (LDZ). The LDZ microhardness is equal to that of the SZ basically. And the HAZ microhardness is higher than both the LDZ and SZ slightly. The results of room temperature tensile test show that the strength and ductility of the wrought sample are slightly higher than the laser repaired samples. Meanwhile, the strength of the laser repaired specimen with repair ratio of 40%(i.e. area fraction of the LDZ on the transverse section of tensile sample within gauge part is 40%)is slightly lower than that of 50% repaired specimen, but the ductility is higher than the latter. Therefore it is favorable to match the strength and ductility of the wrought substrate with the LDZ with low oxygen Ti64 powders as the cladding materials, so as to improve the comprehensive properties of laser repaired Ti64 alloy. The wrought specimen tensile fracture presents a typical ductile characterization, and the repaired specimenshows a complex fractography. From the LDZ to the SZ, the tensile fracture presents a successive transformation from cleavage step to dimple fracture. It can be seen that there is a good corresponding relationship between the fracture morphology and the microstructure of the tensile samples.

Abstract:The surface of MB8 wrought magnesium alloy was treated by HJ-III type ultrasonic impact treating (UIT) machine. The microstructures on the treated surface were analyzed by means of an optical microscope, and the grain refining mechanism of UIT was investigated by High Resolution Transmission Electron Microscopy (HRTEM). The wear resistance of MB8 wrought magnesium alloy was experimentally researched both with the treated and un-treated specimens respectively. The effect of UIT process on the microstructure, micro-hardness were also investigated using scanning electron microscope (SEM) and micro-hardness tester. The experimental results indicated that the grains on the top surfaces of MB8 were highly refined. The severe plastic deformation was formed by UIT, and the thickness of the plastic deformation layer was approximately 180 μm. The microhardness and wear resistance of the treated surface layer of MB8 could be enhanced significantly compared to that of the un-treated specimens. The longer the UIT time, the greater of the microhardness and wear resistance of the treated surface layer of MB8 would be. When the impact current is 1.2A and impact time is 6 min respectively, the microhardness and wear resistance of the treated sample is about 102.8% and 51.83% higher than that of the un-treated specimen, respectively.

Abstract:The flow stress behavior of commercial pure titanium (CP-Ti) was studied by uniaxial tension tests at temperatures ranging from 283SK to 573SK and strain rates from 0.00005-0.005s_-1. The tensile properties of CP-Ti was investigated to determine the quantitative variation of the strain rate sensitivity and the strain hardening by temperature based on Fields–Backofen (FB) model. The results indicates that the strain rate sensitivity of CP-Ti at 283K-423K is not obvious and strain hardening index increases with temperature at 353K-573K. A mathematical model using an updated FB equation based on temperature changing was established to describe the plastic flow stress behavior of CP-Ti. Meanwhile by considering the coupled effects of strain, strain rate and temperature, a modified Johnson-Cook(JC) model was proposed to predict the flow behavior. Compared with the original JC model, the modified JC model shows more agreement with the experimental stress, which validates the accuracy of the modified model describing the plastic flow stress of CP-Ti.

Abstract:High entropy alloy (HEA) Cu29Zr32Ti15Al5Ni19 consisting of two solid solution phases and bulk metallic glass (HE-BMG) with the same composition were successfully prepared separately by casting in a copper mold. The result indicates that the alloy has high glass forming ability. The compressive strength of as cast HEA Cu29Zr32Ti15Al5Ni19 is 1127MPa. HEA Cu29Zr32Ti15Al5Ni19 shows good tempering resistance. The hardness of Cu29Zr32Ti15Al5Ni19 remains 826HV after treated at 750℃ for two hours.

Abstract:Flow behavior and dynamic recrystallization (DRX) critical conditions of 25vol.% B₄C_p/6061Al composite have been investigated by isothermal compression tests at temperatures ranging from 350℃ to 500℃ with strain rates of 0.001s_-1-1s_-1. The stress-strain curves show that DRX is the mainly softening mechanism of the composite, and an Arrhenius-type equation is developed used peak stress. Based on the strain hardening rate curves (θ-σ), the critical strains (ε_c) and critical stress (σ_c) are identified to express the initiation of DRX. The results show that there is a liner relationship between σ_c and σ_p: σ_c= 0.8374σ_p- 0.33708. The Zener-Hollomon parameter is also introduced to describe the effect of deformation conditions on critical conditions: ε_c=2.39×10_-4Z_0.11022. In addition, the steady-state strains (ε_ss) are determined by the θ-ε curves, and then the DRX diagram is established.

Abstract:In this research, the process of hydrodynamic deep drawing of Al2198 was investigated by using finite element simulation experimental works. And the effects of die cavity pressure, blank holder gap and pre-bulging pressure on the forming process and the thickness distribution were analyzed. The research indicated that the pressure inside the liquid chamber and the blank holder gap or blank holder force were the main factors affecting hydrodynamic deep drawing process. And appropriate pre-bulging pressure was beneficial to form a good quality parts with a relatively uniform wall thickness.

Abstract:Because of lateral sparse wave, there is structure difference between central region and periphery in explosive welding interface. However, academic estimations for the difference of interfaces morphology are still in the qualitative level, quantitative analysis methods have not been established. This paper tries to evaluate the difference of explosive welding interface morphology quantitatively. First of all, an elastic-viscous model was established to analyze the forming of wavy interface, and symmetrical 2024 Al explosive welding was carried out for testing. Then the interface images of both central district and periphery were detected by three-dimensional ultra-depth microscopy, and a demarcation line for the central area and periphery was defined based on the impact impulse. Furthermore, the fractal dimensions and multi-fractal spectrums of the images were calculated on the basis of fractal theory. According to the physics meaning of fractal characters of images, the quantitative descriptions have been achieved for explosive welding interface structure difference.

Abstract:Modified PbO₂ electrodes were prepared by electrodeposition in the presence of ionic liquid 1-ethyl-3-methyl-imidazolium tetrafluoroborate ([Emim]BF₄). The electro-catalytic performance of prepared electrodes for the electrochemical degradation of phenol in aqueous solution was investigated. The COD removal of phenol simulated wastewater followed pseudo-first-order rate kinetics. The first-order rate constant with [Emim]BF₄-modified PbO₂ electrodes was 0.00739 min_-1, versus 0.00383 min_-1 obtained with non-modified PbO₂ electrodes. The microstructure of the electrodes was characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy. The electrochemical properties were investigated by Mott-Schottky, steady-state polarization and linear sweep voltammetry techniques. The surface characterization results illustrated that PbO₂ coatings with compact and regular morphology, a higher degree of crystallinity and higher content of oxygen in crystal lattice were anodically grown on Ti substrate from electrolyte containing [Emim]BF₄. Steady-state polarization tests showed that oxygen evolution overpotential on modified electrodes was significantly higher than that on non-modified electrodes. Mott-Schottky tests revealed a markedly lower content of oxygen vacancy in modified PbO₂ samples as compared with the non-modified ones. It was suggested that the enhanced electro-catalytic activity of the [Emim]BF₄-modified PbO₂ electrode towards phenol degradation arose largely from the lower content of oxygen vacancy, which decreased the probability of oxygen transfer from more effective ?OH into less desirable O_lat at the electrode surface.

Abstract:Sliding wear tests were performed of TC4 alloy/GCr15 steel on the MPX-2000 pin-on-disk wear tester. The effect of nano-oxide particles artificially supplied onto the sliding interface on the wear behavior of TC4 alloy was studied by varying the type and diameter of oxide particles. The wear characteristics of alloy were examined by XRD, SEM and EDS, the wear mechanism of TC4 alloy being discussed subsequently. Results showed that the type and diameter of oxide particles had significant influences on the wear behavior of TC4 alloy. Its wear loss was aggravated fleetly by TiO₂ oxide particles, whereas it was improved in the case of Fe₂O_3. The wear loss of TC4 alloy was getting smaller with the decreasing particle diameter of Fe₂O₃, which was almost independent of the applied load. When the TiO₂ was supplied, the wear mechanism of TC4 alloy was mainly abrasive and adhesive wear as the same as that without any additives. The severe-to-mild wear transition occurred when Fe₂O₃ oxide particles were supplied.

Abstract:In this paper, the dynamic mechanical properties and sensitivity of adiabatic shear banding of TC4 alloy having bimodal microstructures were invesgated using Split Hopkinson Bar.The bimodal microstructures with different width of secondary α phase (α_s) were obtained via different heat treatment. The results showed that the width of α_s increased with the decreasing of cooling rate. Under dynamic compression experiments, the dynamic strength decreased as the width of α_s increased; while the dynamic strain exhibited an opposite trend. Under forced shearing experiments, the sensitivity of adiabatic shear banding decreased as the width of α_s increased. Besides, the sensitivity of adiabatic shear banding increased for the same microstructure with the increasing of impact velocity. Combined with the effects of volumn fraction of transformed β and width of α_s on dynamic mechanical properties and sensitivity of adiabatic shear banding of TC4 alloy, the bimodal microstructure obtained by the heat treatment,980℃/1h/A+550℃/4h/A, had good high strength and low sensitivity of adiabatic shear banding matching. The optimal bimodal microstructure had a volumn fraction of transformed β matrix of 80.7% and the width of α_s plates was 1.74 μm.

Abstract:Microstructural characteristics of high-purity titanium during dynamic compression at low-medium strain were studied by optical microscopy (OM), electrical back-scattered diffraction (EBSD) techniques and transmission electron microscopy (TEM). The results show that the original grains are gradually refined by twin-twin, twin-dislocation and dislocation-dislocation interactions. The predomiant twinning system is {11-22} twinning at the beginning of deformation, {10-12} twinning become to the main twinning modes when strain reached 0.2. The orientations of each twinned grain are altered by twinning that further facilitate dislocation glide in interior grains. Though dislocation slip and twinning always work together to coordinate macroscopic plastic deformation, the deformation process of high-purity titanium during dynamic compression is experienced dislocation slip to deformation twinning and dislocation slip again.

Abstract:Spiral grain selector is a very important part of manufacturing process of single crystal blade, which is the key component of the aero-engine and industry gas turbine. Finite element simulation and experiments are used for researching the temperature effect of spiral grain selector, the grain structure and grain growth in the directional solidification process of DD6 superalloy. The results show that simulation method can well predict the temperature change of directional solidification process, and the grain microstructure simulation is similar to the competitive growth of grain according to the experimental samples. Because the location of the grain is replaced, whose orientation is different from the direction of temperature gradient, the mean radius of grain increases with increasing height in the starter block, while the grain density declines. The simulation results of grain morphology in the spiral part are consistent with experimental pictures from the EBSD orientation mapping technology. The grain is more advantage to grow in the spiral part, which is located in the interior and upper part of the spiral channel longitudinal section.

Abstract:_{The effect of carbon content on the solidification microstructure of single crystal superalloy DD90 was investigated. The results show that, with the increase of C composition, the value of primary dendrite arm spacing increases, and the range of solidification temperature expands. With the increase of C composition , the content of carbide increases, the carbide morphologies change from blocky shape to Chinese script-type, then link together to skeleton –like. With the increase of C composition, the number of γ/γ′ eutectic decreases, coarse primary γ′ phase decreases. With the increase of C composition, the solidification segregation of metal elements in solid phase generally deducts. C addition promoted the degree of segregation of Al, while reduced the degree of segregation of Re, Mo, W.}

Abstract:Based on microscopic phase-field model which is coupling both exterior load and cyclical temperature, growth orientation for phases and distribution of elements during precipitation in nickel based alloy was studied. The result showed that: the effect of cyclical temperature cannot change the growth orientation and the precipitation order of phases. With the effect of cyclical temperature, L1₂ precipitated first when the content of Al was higher, DO₂₂ precipitated first when the content of V was higher, and both L1₂ and DO₂₂grew perpendicular to the direction of tensile stress. When tensile stress existed in [001] and L1₂ precipitated first, DO₂₂ prefer to grow along [100]. When tensile stress existed in [100] and DO₂₂ precipitated first, L12₂ prefer to grow along [100]. With the reducing of higher temperature of cyclical temperature, the fluctuation range of volume fraction for L1₂ during cyclical temperature decreased obviously and the fluctuation range of volume fraction for DO₂₂ during cyclical temperature changed a little.

Abstract:The phase equilibria related with the liquid phase at 1000℃ in low-Ni side of the Nb-Ni-Ti system have been investigated by SEM, EPMA, XRD and DSC. It has been shown that there exists the liquid phase which could be in equilibrium with the continuous solid solution (Nb,betaTi) and compound TiNi in the low-Ni side of the Nb-Ni-Ti system at 1000℃. The liquid phase field originates from binary Ti-Ni system and extends to the 3.7%Nb (atomic fraction). The solid solubility of Nb in the compound TiNi is about 8.0%. At 1000℃, there are two three-phase fields consisting of Liquid+(Nb,betaTi) TiNi and (Nb,betaTi) TiNi XB in the Nb-Ni-Ti system, XB is the compound with the composition of 34.0Nb-44.9Ni-21.1Ti% and hexagonal structure. The broad two-phase field (Nb,betaTi) TiNi exists between the two three-phase fields. In this two-phase field, the Ni content in the continuous solid solution (Nb,betaTi) is about 3%, but the Ti content varies from 6.6 to 39.9%. The thermo-stability of the compound Ti2Ni has been improved by the solution of Nb atoms, but the Ti2Ni with 3.7%Nb could not exist at 1000℃.

Abstract:Aiming to reduce the friction coefficient of WC-Co coating, the GO and WC-Co spraying powder was uniformly mixed by wet milling. The grapheme oxide modification WC-Co coating was prepared by detonation gun spraying. With the help of XRD, SEM and EDS instrument, the existence of graphene, microstructure and chemical composition of the coating were analyzed. Mechanical and wear properties of the coating were studied by means of micro-hardness tester, universal tensile and wear testing machine. The results show that layer graphene film was existed in the graphene modified coating. The coating has the dense and uniform structure. The adhesive strength and micro-hardness of the coating was 82MPa and 1024 HV0.3. The friction coefficient of WC-Co coating was decreased by 30% compared with the graphene modified coating. The addition of graphene was highly improved the wear resistance of the WC-Co coating.

Abstract:Contact-reaction brazing is used to bond AZ31 joints in order to improve the microstructure and wettability of AZ31 magnesium alloy brazed joints. This is achieved by using an AgCuZn interlayer during the brazing process without the use of a flux. The results show that a defect-free brazed joint can be obtained when the AgCuZn interlayer is completely dissolved at 500 °C for 15 minutes. The microstructure in the brazing seam consisted of multiple eutectic structures. The second phase was composed of granular and short rod-like features. Both the granular and the short rod-like structures were uniformly distributed in the continuous matrix. A small amount of primary crystal taking on cloud state is present in the brazing seam center. X-ray diffraction and energy spectrum analysis indicate that the second phase consisted of an α-Mg solid solution containing high amounts of Ag, Cu, and Zn, while the basal body consisted of an AgMg3 compound and small amounts of CuMgZn compound. The mean shear strength of the brazed joints was about 108.9 MPa. Both sugar granules and cleavage steps were clearly observed in the tensile shear fracture morphologies with mixed fracture characteristics in both intergranular fractures and transgranular fractures. The AgCuZn-base interlayer influenced the microstructure and mechanical properties of the brazed joints.

Abstract:The microstructure and element distribution of AZ91 alloy have been changed by adding the mischmetal of lanthanum and cerium (La, Ce). The existence forms of La and Ce elements in AZ91 alloy are different. Part of them can be dissolved in the α-Mg solid solution, the others formed the different intermetallic compounds with a chemical composition Al₄(La,Ce)or Al₁₀Ce₂Mn₇, Al₄(La,Ce)is in acicular shape and Al₁₀Ce₂Mn₇ is in granular shape. The fraction of β phase in AZ91 alloy decreased obviously with the addition of misch, and the distribution of Al element transferred from the grain boundaries to grain internal area. The study results on the corrosion behavior of AZ91 magnesium alloys with addition of misch in de-icy solution under wet-dry circles showed that a shift of the corrosion potential (Ecorr) towards more negative values is observed for all the alloys with misch addition, but their corrosion current densities (Icorr) are much lower compared to that of the AZ91 alloy. The scanning electrochemical microscopy (SECM)test results revealed that the addition of could reduce the number of electrochemical active points on the surface. In addition, the compactness of corrosion product film of magnesium alloy was increased with addition of misch.

Abstract:Effect of trace amount of Ga2O3 addition on the changes of the wettability and spreadability of CsF-RbF-AlF3 flux and Zn-Al filler metal were investigated on 6063 aluminum alloy and Q235 low-carbon steel. The experimental results indicated that trace amount of Ga2O3 addition in the flux could obviously promote the Zn-Al filler metal to wet and spread on the surface of 6063 aluminum alloy and Q235 low-carbon steel, in which the optimum range of Ga2O3 was 0.001~0.003wt.%. According to the XRD results of the flux residua and the thermodynamic calculation, it could be concluded that the trace amount of Ga2O3 addition could enhance the solubility and reactivity of CsF-RbF-AlF3 flux to the surface oxides on 6063 aluminum alloy and Q235 low-carbon steel. On the other hand, Ga2O3 could also be reduced to Ga. Because of its skin effect, Ga could enrich on the interface of filler metal and base metal and effectively decreased its interfacial tension, which could improve the wettability and spreadability of the filler metal.

Abstract:High strength steel DP980 was welded using fiber laser, and the temperature field was evaluated via numerical simulation. The results reveal that the peak temperature of weld center reached 3204 ℃ and then cooled rapidly。The fusion zone contained mainly martensitic microstructure with hardness 30% higher than that of the base metal. The ultimate tensile strength of the fusion zone reached 1115.7 MPa, while the elongation was 49.1% of the base metal. The stress-strain curve of the softened zone exhibited obvious yield platform, and the ultimate tensile strength (850.7 MPa) was lower than the base metal (986.9 MPa) significantly. The ultimate tensile strength of the welded joint reached 87.1% of base metal, while the elongation reached 32.7%. All the tensile and Erichsen test samples failed at the softened zone. The major strain of the base metal was higher than the welded joint.

Abstract:Continuous heating tests of without addition and addition rare earth 30Mn steel were investigated by using differential scanning calorimetry (DSC). The transformation activation energy and kinetic factor were obtained by Kissinger and JMA equation. The results show that the values of the starting temperature Ac₁ and the end temperature Ac₃are raised with rare earth addition. The activation energy can be increased by 186 kJ/mol, and the value of kinetic factor n is decreased. The austenitic transformation process of without addition and addition rare earth 30Mn steel have been described as two stages, and different stages have different grain growth mechanism.

Abstract:Nickle base single crystal superalloys DD407 were welded by electron beam welding. the morphology and distribution of crack were analyzed by optical microscopy and scanning electron microscopy. the chemical component between dendrite dry and interdendritic area was measured by EDS. the segregation ration of elements was calculated and the causes of crack formation was analyzed. The results show that: longitudinal cracks, transverse cracks, crater cracks, intergranular cracks mainly were produced in fused region of DD407 under the thermal effect of the electron beam. With the increasing of electron beam current, the content of solidification cracks increase firstly and then decrease when other parameters remain unchanged. low melting point eutectics gather and form a low-melting liquid films due to the serious segregation of alloying elements in miscellaneous grain zone,thus the solidification cracks are often formed in miscellaneous grain zone in the solidification shrinkage tensile stress.

Abstract:By applying laser metal direct forming technology into the manufacturing of the customized titanium implants, titanium implants can be directly formed according to their CAD model. This method has the advantage of short manufacturing cycle. Additionally, the customized titanium implants manufactured in this method have good mechanical properties. The influences of curvature effect and inclination angle on the geometric precision of laser metal direct forming parts were studied for the establishment of the model design criteria. Therefore,the formed titanium implant manufactured could achieve high precision. Both mechanical properties and chemical composition of the manufactured customized titanium implants comply with relevant national and pharmaceutical industry standard. Two cases of customized titanium implants manufactured by laser metal direct forming have been successfully used in clinical and have achieved good results.

Abstract:Stress-controlled high-cycle fatigue performance of ultra-fine grained commercial purity titanium (UFG CP Ti) was conducted with a loading frequency of 25 Hz and a stress ratio R=-1 at room temperature. The relation between stress amplitude and cycle numbers to failure was fitted, and the fatigue fracture surface of UFG CP Ti specimen was also investigated. The results showed that the fatigue limit of annealed UFG CP Ti specimen at 200℃ for 60 min was 376.5 MPa, which increased 56.5 MPa compared with the unannealed one. Moreover, the fatigue cracks mainly initiated from the surface of fatigue specimen. The annealed UFG CP Ti specimen exhibited the smaller fatigue striation spacing and lower crack propagation rate than the unannealed one, indicating a higher room temperature fatigue performance.

Abstract:TA15 titanium alloy bulk specimens were prepared by spherical powder in the way of laser deposition manufacturing. The effect of alpha plus beta phase zone annealing treatment on mechanical properties, microstructure of laser deposition manufacturing TA15 titanium alloy and lamellar deformation mechanism has been studied by optical microstructure (OM) and scanning electron microscopy (SEM). The experimental results showed that microstructure was basketweave structure or near basketweave structure after alpha plus beta phase zone annealing treatment, pattern and size of alpha phase was affected effectively by annealing temperature. The mechanical properties after annealing still showed the anisotropy in the different direction: the strength was low and the plasticity was high in deposition direction and the strength was high and the plasticity was low in vertical deposition direction. The interlayer binding zone slip deformation played a vanguard role and the columnar crystal grain boundary had bound effect on alpha phase slip deformation. Microhardness was effected by the amount of alpha phase while it changed little with the increase of annealing temperature. Alpha lamellar in basketweave structure under the stress changed from near orthogonal to near parallel to the direction of stress, staggered arrangement of alpha lamellar generating resistance each other when it was in the state of slip deformation. Both deposition direction and vertical deposition direction had same tensile fracture modes which was ductile fracture after alpha plus beta phase zone annealing treatment.

Abstract:The technology of laser deposited repair was used to repair TA15 alloy with milling groove damage, and the fatigue crack nucleation and growth behaviors were investigated. Fatigue fracture surfaces and longitudinal sections of specimens were examined by optical microscopy and scanning electron microscopy. Results indicated that specimens were broken in the repaired zone and the fatigue properties are microstructure-sensitive. The crack nucleation region was characterized by the crystallographic cleavage facets of α lamellae and tearing of β matrix. The size and morphology of the cleavage facets were the same with α lamellae. The crack tended to propagate along the border of α lamellar and its propagation direction was parallel or perpendicular to α lamellar. After solution-aging treatment, the microstructure-sensitive size reached individual small units of a single lamellae, presenting a single α/β tearing deformation along the misalignment of silp direction in two colonies and a clear arrangement of bunch-α ". A finer, more oriented lamellar structure were obtained to make it easier for fatigue crack deflection, increased the length of the crack path, thereby consuming more crack propagation energy.

Abstract:Using Ti and Si elemental elements mixed powder as raw material, Ti-Si alloy coating was successfully fabricated on the surface of titanium alloy by laser alloying. Microstructure morphology, composition and phase of the coating were investigated. Microhardness and tribological properties under dry friction and wear conditions were tested. The results show that: the Ti-Si coating under the appropriate parameters of laser alloying prepared is uniform and dense, crack-free, and combined with a generally good metallurgical TC4 base; coating microstructure is consisted of needle-like α-Ti matrix and network distribution of Ti5Si3/β-Ti eutectic (room temperature is Ti5Si3/α-Ti) composition; the hardness of the coating is between HV 660 ~730;compared with TC4 titanium alloy, the average friction coefficient decreases (0.39VS0.45) and wear resistance increased 2.4 times.

Abstract:The microstructure and mechanical properties of annealed Zr-4 alloy subjected to surface mechanical rolling treatment (SMRT) have been systematically investigated. The effect of rolling passes and rolling depth per pass on the thicknesses of NG (nano grain) / UFG (ultrafine grain) layer and deformed layer in SMRTed Zr-4 alloy are studied. The optimized process parameters are 8 passes and depth of 40 μm per pass. A gradient microstructure consisting of NG/UFG layer, deformed layer and CG layer are produced in the SMRTed Zr-4 alloy from the treated surface to the matrix with thicknesses of 100μm and 300μm. The microhardness on surface significantly increases due to SMRT. The yield stress and ultimate tensile strength of SMRTed Zr-4 alloy are 352MPa and 600MPa, increase by 7% and 9%, respectively. And the elongation is slightly reduced.The rule-of-mixture for strength can be used to estimate the combined strengths of Zr-4 alloy with a combination of NG/UFG layer, the deformed layer, and the CG matrix.

Abstract:High temperature oxidation resistance coating were prepared by a certain ratio of Al powder, Sn powder, SiO2 powder, styrene acrylic emulsion, polyvinyl alcohol, sodium carboxymethyl cellulose mixed. The effects of different heat treatment temperature and heat treatment time on antioxidant properties were discussed. The microstructure of the exposed surface and spraying surface, coating microstructure, elements diffusion and interface phase structure were analyzed by optical microscope, field emission scanning electron microscopy, energy spectrum analysis instrument and X-ray photoelectron, respectively. The results show that aluminum high temperature oxidation coating effectively prevent surface oxide production formed on the surface of titanium ingot during thermal processing, Al₂O₃-TiAl and TiAl₃-Ti phase with a good protective effect are formed in the interlayer, it is worthy noted that the excellent heat treatment temperature and holding time are 1050 ℃ and 8 h, respectively.

Abstract:In order to improve the Nb-1Zr alloys’ oxidation resistance, a series of NiCr coatings with different composite structure were deposited on Nb-1Zr alloys by Plasma enhanced ion plating bellow 300℃. By means of isothermal oxidation, NiCr coatings’ oxidation resistance property was studied in detail. The mechanism of invalidation and oxidation resistance of NiCr coating with different microstructure was revealed. The results showed that a channel for oxygen diffusion could be formed by the micro holes communicating with each other in the single layer NiCr. So the Nb-1Zr matrix near the interface would be oxidized firstly and Nb₂O₅ based oxide powder was generated which gradually was increased along with the oxidation time, causing the breakage of coating. That “through holes” can be significantly reduced by NiCr multilayer composite structure, but the coatings’ failure mode was not changed. By introducing the Cr interlayer, the diffusion of oxygen would easily be absorbed and a dense Cr₂O₃ layer was formed which can discourage the further diffusion of oxygen into the Nb matrix. And also a dense Cr₂O₃ layer could also be formed on the surface of Cr/NiCr multilayer coating by diffusion of Cr. As a result, the Nb-1Zr alloy’s oxidation resistance could be improved. After oxidizing at 600℃ for 500 hours, The weight gain rate of Nb-1Zr alloy with Cr/NiCr multilayer composite coating was only about 0.08 g/m₂.h.

Abstract:The effect of anodic aging time on the constitution, structure and semiconductor properties of passive film formed on an Fe30Mn9Al alloy in 1mol/L Na₂SO₄solution were studied by using combined Auger electron spectroscopy (AES) / X-ray photoelectron spectroscopy (XPS) analysis and the measurement of Mott-Schottky curves. The passive film formed on Fe30Mn9Al alloy in 1mol/L Na₂SO₄solution for 15 min has two layers of inside and outside, and the outside layer has the characteristics of n-type semiconductor, composed of Fe₂O₃, Al₂O₃, Mn₂O₃, FeOOH and AlOOH, the inside layer has the characteristics of p-type semiconductor, composed of MnO. The passive film formed on Fe30Mn9Al alloy in 1mol/L Na₂SO₄solution for 5 h has the characteristics of n-type semiconductor, composed of FeOOH , AlOOH and Mn₂O₃. As the anodic aging time increases from 15 min to 5 h, the Al and Fe contents are enriched and the Mn is depleted, MnO dissolved, the Al and Fe oxides are changed to the Al and Fe hydroxides; The donor densities N_D of the passive film decreased from 2.58′10₂₁ cm_-3 to 1.96′10₂₁ cm_-3, the flat band potential E_fb decreased from -283 mV to -366 mV, respectively.

Abstract:The butt joints of 6061-T6 /AZ31B with a thickness of 3 mm were obtained using laser welding with a high laser power and welding speed. The macro-morphology, microstructure and fracture feature of the joints were analyzed by the stereo microscope, scanning electron microscope (SEM). The composition of microstructure and fracture surface was analyzed by Energy Dispersive Spectrometer (EDS). The microhardness and tensile strength of the joint were tested. The results showed that the content of intermetallic compound was different in different weld region. There was a large amount of intermetallic compounds Al₁₂Mg₁₇ in the weld zone and fusion zone near AZ31B side. The other areas were mostly the mixed structure of α(Al) and Al₂Mg₃. The presence of intermetallic compounds leaded to the higher hardness of the weld compared to the base metal. The hardness fluctuated in value because of the different intermetallic compounds and their various contents. The tensile strength of 6061-T6/AZ31B dissimilar butt joints by laser welding was up to 34 MPa. It was found that the fracture always occurred in weld zone near AZ31B side, and the fracture mode was typical brittle fracture.

Abstract:In this paper,the AZ80 magnesium alloy billets of size of 100mm×50mm×170mm was extruded by CEEOP.The effect of 1~4 pass deformation of CEEOP to the equivalent strain、 microstructure and mechanical properties of AZ80 magnesium alloy through simulation、OM、tensile test and hardness test.The results show that with the increasing of CEEOP pass,the grain size was more small and uniform;the grain size could be defined from 200μm to 6μm after one-pass;after four-pass, the size of equal-axial grain was reduced to approximately 1.5μm and the distribution was uniform,furthermore,the mechanism of grain refinement is mechanical fragmentation and dynamic recrystallization;the grain refinement effect was not obvious after two-pass.The mechanical properties have been greatly improved compared with the annealed alloy. One-pass deformation of CEEOP can significantly improve the hardness of annealed alloy from 61.5HB to 83.07HB.Similarly,four-pass deformaion can also obviously improve that from 61.5HB to 86.27HB.The ultimate tensile strength and yield strength via one-pass can improve from 230.9MPa ,115MPa to 262.7MPa ,155MPa ,respectively.And after four-pass,they would increas to 294MPa ,170MPa,respectively. Compared with the microstructure and mechanical properties of ECAP,at the same deformation temperature and strain accumulation,CEEOP can better refine grain and improve the tensile strength and yield strength of the material.

Abstract:Abstract: The effects of heat treatment on the tensile properties and fatigue crack propagation（FCP） behaviors of new Al-Cu-Li alloy were investigated. The microstructure and fracture morphology were observed and analyzed by OM, SEM and TEM. The results indicate that the new Al-Cu-Li alloy can obtain the best comprehensive properties under 540℃/1h solution treatment and （12?AaRT（5d） 145℃（20h））aging treatment condition, with σb =443Mpa，σ0.2 =397Mpa,δ=16.5%，da/dn=1.34*10-3mm/cycle（△K=30 Mpa*m1/2）. The two-step artificial aging can improve the resistance to crack propagation of the alloy by promoting the precipitation of the fine, dense and uniform T1(Al2CuLi) phase in the matrix, while the strength is also high; In T8 temper; the alloy will precipitate some relatively coarse T 1 phase ,θ′phase and a few S′phase which achieve the demand of the high strength ,while not satisfying the requirement of crack propagation resistance . In T3 temper ,the alloy has a poor strength with the few strengthening phase existed.

Abstract:Electrochemical corrosion behaviors of Zn4Al3Mg-xIn solder alloys were studied in this work by potentiodynamic polarization measurements. And the high-temperature oxidation resistance of the solders was also investigated by thermogravimetric analysis (TGA). The results show that: the corrosion potential of Zn4Al3Mg solder is less than -1.15V, which means the corrosion tendency of Zn4Al3Mg-xIn alloys can not be neglected, and the corrosion potential decreased with the increase of In content. Obvious regional corrosion and pitting corrosion were observed on the surface of Zn4Al3Mg-xIn alloys by SEM.The TGA results indicate that slow progress of oxidation took place at 260 ℃, Zn4Al3Mg-xIn alloys show good oxidation resistance.

Abstract:The precursor powders were successfully prepared by GNP method with Ammonium molybdate((NH₄)₆Mo₇O₂₄.4H₂O), Cupric nitrate(Cu(NO₃)₂.3H₂O), Glycine and Ethylene diamine, followed by reducing in H₂ at 700℃ to convert into Mo-20Cu powders. Effects of different pressure on sintering body of Mo-Cu alloy that sintered at 1150℃ were studied. The results show that the nano-powders which is fine with size of 70~80nm can be prepared by GNP-H₂ reduction method. The relative density of Mo-Cu compact sintered at 1150℃ can achieve 99.7% of the theoretical and the microstructure of the compact distributes homogenously. With increase of pressure, the hardness, electrical conductivity and thermal conductivity will be enhanced with limit.

Abstract:The melt-spun Ce17Fe78B6 ribbons were prepared by melt-spinning at various chamber pressures. The effect of chamber pressure on the magnetic property and microstructure of Ce17Fe78B6 alloy was investigated. Results showed that the magnetic property and microstructure of the Ce17Fe78B6 alloy were sensitive to the chamber pressure. With the chamber pressure increasing, the coercivity increased while the remanence and maxium engery product reached a maximum value at 0.05 MPa. The results of X-ray diffraction and transmission electron microscope showed that the Ce17Fe78B6 alloy had the highest volume fraction of hard magnetic Ce2Fe14B phase and uniform microstructure at a chamber pressure of 0.05 MPa, resulting in optimal magnetic properties.

Abstract:Additives with different structures and properties were selected to prepare the silver powder under the same experimental conditions. The effect of the different additives on the morphology and particle diameter of the silver powder was compared and analyzed. The results show that, using the no branched or less branched long-chain polymer compound as additive is more helpful to prepare the silver powder with smooth surface and spherical shape. In this paper, based on the additive of PVP K30, the silver powder with excellent dispersion, spherical shape and good crystallization was prepared successfully by adjusting and optimizing the experimental parameters. The particle size is about 2.5 ~ 3 μm and the tap density is 4.2 g/cm3, which can meet the required index of silver powder used for the solar electronic paste.

Abstract:The immersion gold process based on electroless Ni-P alloy substrate with three P contents (4%, 9% and 11%) was investigated by X-ray fluorescence spectrometer, atomic force microscopy and open circuit potential measurementand analysis. The effects of temperature on the gold deposition process were also discussed. The results show that the deposition rate and electrode potential are changed during the immersion gold process. In the same temperature, a higher P content often leads to a high electrode potential and a low initial deposition rate. However, the effect of temperature on immersion gold is relatively complex. In the range of 50-80℃, a high temperature results in a positive potential and a better surface morphology of the gold coating with a smaller surface roughness, while a more negative potential and a bigger surface roughness are obtained at a higher temperature(90℃).

Abstract:2195-T8 and 2219-T6 sheets were successfully welded in the current research.With constant tool rotation speed (TRS), effects of travelling speed (TS) and advancing side material (AS material) on the mechanical properties of the joint were studied. The results indicate that higher travelling speed improves the mechanical properties of the FSW joint. Whichever the AS material was, fracture always occurred at the boundary of the welding nugget zone (WNZ)/thermomechanical affected zone (TMAZ) to the 2219 side. Longitudinal tensile tests show that mechanical property of the WNZ is better than that at the boundary of WNZ/TMAZ to the 2219 size.

Abstract:Abstract: 2024-T4 aluminum alloy was treated by micro-arc oxidation in the silicate system electrolyte with different concentrations of nano Cr2O3 microparticles. The surface morphology and the cross-section morphology of ceramic coatings were observed by SEM. The distribution of main component of ceramic coatings along the cross-section was analyzed by EDS, and the phase structure of ceramic coatings was analyzed by XRD. The hardness of ceramic coatings was measured by nano indentation hardness tester. The surface roughness of ceramic coatings was measured by roughness meter. The friction coefficient of ceramic coatings was measured by Friction and wear tester. The wear volume of ceramic coatings were measured by laser confocal microscope and the wear rate was evaluated. The morphology of wear tracks was observed by SEM. The results show that the composition of Cr2O3 was discovered in the ceramic coatings after nano Cr2O3 microparticles were added to the electrolyte. The hardness of ceramic coatings is the highest, the friction coefficient of ceramic coatings is the minimum, the wear rate is the lowest, and the wear resistance of ceramic coatings is the best under the condition of concentration of nano Cr2O3 microparticles being 2.4 g/L in the electrolyte.

Abstract:The composition hardness and morphology of vanadium carbide(VC) coatings and their growth kinetics have been investigated by X-ray diffractometer (XRD), the electronic probe microanalysis(EPMA) scanning electron microscope (SEM), vickers indenter and energy dispersive X-ray spectrometry (EDX) on the 3Cr13 stainless steel, which was treated by FLiNaK salts for different time by the thermal diffusion carbide coating process (TD). It was found that VC coatings with the thickness of 3~5 μm formed on the surface of 3Cr13 stainless steel for different treatment time . The coatings displayed petal-shaped and contained a handful of Si and Fe.The average hardness of the VC coating up to 3222 HV and there was a parabola relationship between the thickness of the coatings and the treatment time. VC coatings were covered by rimous SiO₂ phases with the thickness of hundreds of nanometers. The cracks of SiO₂ phases resulted from the tensile stress during the cooling process,which derived from the different thermal expansivity between VC coating and SiO₂ phase. The present study also indicated the potential application of FLiNaK salts in TD process.

Abstract:Coating on zirconium alloy is one of important way to improve the properties of fuel cladding under nuclear power plant accident. The research progress of coating on the surface of zirconium alloy are summarized in this article, which include types, preparation process, microstrutures, steam oxidation resistance properties and corrosion resistance properties. The selection basis of coating, and the relationship between preparation process, microstructure and steam oxidation resistance properties are discussed. Some problems in the present researches and development of coating are analyzed. The results can provide valuable references for promoting development of coating on nuclear fuel cladding.