Abstract:The effect of heat treatment on the microstructural and tensile properties of an ultrasonically treated extruded Mg-6Zn-0.5Y-2Sn alloy was investigated. The results showed that after both the aging treatment and “solid solution and aging” treatment, the grain size became more uniform. The MgSnY and Mg2Sn phases were much more dispersed and increased in amount. In addition, both the aging and “solid solution and aging” treatments improved the yield strength of the test alloys. Specifically, the aging treatment significantly improved the yield strength from 165 MPa to 269 MPa, which is an increase of 63.1 %. The precipitation strengthening, which is derived from the collective strengthening effect of the MgSnY and Mg2Sn phases, was the optimal factor for improving the yield strength in the test alloys with heat treatment. Moreover, the aging treatment more effectively improved the comprehensive tensile properties of test alloy compared with the “solid solution and aging” treatment. The mechanisms for the experimental observations were also discussed in this research.

Abstract:The microstructure evolution and mechanical properties of Mg-3.4Y-3.6Sm-2.6Zn-0.8Zr alloy after different heat treatment experiments were investigated by differential thermal analysis (DSC), optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and tensile test, and the optimum heat treatment systems composing of solid-solution treatment at 500°C for 15 hours and aging treatment at 225°C for 40 hours were proposed. After the solution treatment at 500°C for 15 hours, the layer long period stacking ordered (LPSO) structure disappears, whereas (Mg,Zn)3(Y,Sm) at the grain boundary dissolves into a granular state from the reticular phase, and a large number of long strip phases Mg12(Y,Sm)Zn are formed at the same time. After the aging treatment, a large number of dispersed β′ phases precipitate into the α-Mg grains and it is beneficial to improve the yield strength of the experimental alloy. The yield strength (YS), ultimate tensile strength (UTS) and elongation (EL) of the experimental alloy are 170.0 MPa, 260.8 MPa and 14.1%, respectively. The fracture mode changes from intergranular to transgranular fracture after the heat treatment process.

Abstract:Abstract: The stress-strain curves of AZ80 magnesium alloy are tested by thermal simulation experiment, which the deformation temperature is from 533K to 683K, and strain-rate is from 0.001 to 10 s-1, and deformation degree is 50％. The grain size of dynamic recrystallization (DRX) increases with rising of deformation temperature and reducing of strain-rate. According to the Arrhenius equation and experiment data, the energy of thermal activation of AZ80 magnesium alloy is determined, and a kind of constitutive equation of AZ80 magnesium alloy is established. According to the Sellars equation, the dynamics model of AZ80 magnesium alloy is established, which is defined as the relationship between the volume fraction of DRX and deformation temperature and strain-rate. The kinematics model of AZ80 magnesium alloy is established, which is defined as the relationship between grain size of DRX and deformation temperature and strain-rate. The calculated results of grain size of DRX are in agreement with that of experiment, and relative errors are less than 11.8%. The relationship model between critical strain and steady strain of DRX with deformation temperature and strain-rate are established.

Abstract:Multi-scale models for the unidirectional carbon fabric reinforced magnesium laminates were generated according to the characteristics of its realistic microstructure which included the crosswise and lengthwise unit cell model in microscale and structural unit cell model in mesoscale. The macro mechanical property Young’s modulus was calculated from the mesoscale model. The required properties for mesoscale model during simulation was obtained from microscale model. The Young’s modulus for C_f/AZ91D laminates in different layup modes were predicted by use of multi-scale modeling technique and verified by corresponding experiments. It is shown that multi-scale models can be used to predict the Young’s modulus of laminate composites in different layup modes with the same trend but larger than the experimental results a little bit. It is caused by the perfect assumption of no degradation for matrix alloy and fiber during fabrication. The multi-scale modeling technique proposed in this paper is meaningful for the laminate composite design.

Abstract:Magnesium alloy sheet rolling has special control requirements for the temperature of the work rolls, in this paper, the temperature control of the rolls was controlled by fluid-solid coupled heat transfer. Based on the finite difference method, a differential model for the heat transfer process of roll and thermal oil was established, which was complemented by the corresponding experimental verification. A fluid-solid coupling heat transfer model was also established by FLUENT, giving the roll temperature rise curve, the surface temperature and the cross-section temperature distribution during the heat transfer process. The results showed that the temperature near the roll operating side is the highest and the temperature decreases gradually from the operating side to the driving side, and the temperature difference range between the operating side and the driving side is 5-12°C and is almost unaffected by the fluid temperature and speed. The maximum temperature difference between the inner wall and the outer wall of the roll is 6°C, which can be considered that the radial temperature distribution is even. Under different fluid temperature and velocities, the temperature of the roll rises with trend of decreasing rate, and when the fluid temperature rises and the velocity increases, the temperature rise of the roll becomes faster. After the roll stops heating, its surface temperature does not begin to drop immediately and continue for a period of time, which was about 5-8 minutes, and the temperature and speed of the fluid have less effect on the extended time. The calculated values of the average roll surface temperature agree well with the experimental values, the maximum relative error is 8.3%, which verifies the correctness and effectiveness of the finite differential model, and as part of the magnesium alloy plate rolling model, it is conducive to the isothermal control of the roller in the rolling process and realizes isothermal rolling control of magnesium alloy plate.

Abstract:The microstructure and mechanical response of as-cast and extruded Mg-2Zn-1Mn-xY alloys (Y content of 0, 0.8 and 2.2 wt.%) have been investigated by optical microscope (OM), scanning electron microscope (SEM) with X-ray energy dispersive spectrometer (EDS), and X-ray diffractometer (XRD). The experiment results reveal that the addition of Y not only decrease the grain sizes of both as-cast and extruded alloys, but also effectively reduce the basal texture intensity of extruded alloys. These are two key reasons for the improvement of the strength and ductility of Mg-2Zn-1Mn-xY alloys, simultaneously. The optimized Mg-2Zn-1Mn-xY alloys after extrusion exhibits an attractive mechanical performance. Compared with the matrix material Mg-2Zn-1Mn, its yield strength increases from 164 MPa to 204 MPa, the ultimate tensile strength increases from 237 MPa to 298 MPa and the elongation increases from 12% to 18%.

Abstract:The effect of adding 0-2.0 wt.% Zn to the Mg-8Al-2Sn alloy was investigated by analyzing the microstructures and tensile properties. The results revealed that the phase compositions of Mg-8Al-2Sn-xZn alloys are α-Mg, Mg₁₇Al₁₂ and Mg₂Sn phases. The morphology of eutectic phases of the as-cast alloys was changed from normal eutectic to divorced eutectic with Zn addition. Grain sizes of the alloys were uniform after hot extrusion with Zn addition. Dynamic precipitation of the second phases was promoted by the addition of Zn during hot extrusion. The second phases coarsened in Mg-8Al-2Sn-2Zn alloy. Precipitates formed during the aging treatment and the amount of which increased with the addition of Zn content. Besides, the ultimate tensile and yield strength of the extruded and aged alloys gradually increased with the addition of Zn content. The results showed that Mg-8Al-2Sn-2Zn alloy has the best mechanical property that the ultimate tensile strength, yield strength and elongation of the as-aged alloy were 385 MPa, 291 MPa and 6.44%, respectively.

Abstract:Microstructures and mechanical properties of Mg-5Y-0.6Zr-xNd (x=0, 0.5 and 1wt.%) alloys under various heat treatment conditions were investigated by optical microstructure (OM), scanning electron microscope (SEM), X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and tensile tests. Results showed that with increasing content of Nd, the amount of second phases Mg24Y5 and Mg14Nd2Y (β) was increased in the matrix. Minor Nd addition can reduce the stacking fault energy of α-Mg and promote the dynamic recrystallization during hot-rolled process. As the Nd content increases, the volume fraction of static recrystallization was promoted obviously. The average grain size of Mg-5Y-0.6Zr-0Nd alloy after annealed treatment can be refined to 3.73 μm. Tensile strength of as-rolled alloys increased with the addition of Nd, while the elongation exhibited an opposite change tendency. As-rolled alloy sheet with 1.01 wt.% Nd exhibited the remarkable mechanical properties, which the values of ultimate tensile strength, yield strength and elongation were 336 MPa, 278 MPa and 16.3%, respectively. Based on the microstructure observation, the changes of mechanical properties have been discussed.

Abstract:Ball spinning often requires a continuous cooling of the deformation zone due to the large amount of deformation heat generated by the continuous point-by-point molding characteristics. According to the low forming temperature of magnesium alloy, this paper uses friction and deformation heat to replace the heating process of the thin-walled magnesium alloy tube in ball spinning process. The heat generation laws under different process parameters are calculated by finite element simulation. The results show that the temperature in the spinning deformation zone increases with the increase of rotating speed, thinning amount, feed ratio and friction coefficient. For these four parameters, the friction coefficient has little effect on the temperature increase. The amount of thinning is the most sensitive to the increase of temperature, the effect of mold speed on the increase of temperature is little, and the friction coefficient has the least influence on the temperature rise. Under high speed and larger amount of thinning, the temperature of the deformation zone can reach more than 220℃, which can meet the temperature requirement of hot forming of magnesium alloy. The results of non-contact temperature measurement in the deformation zone show that the simulation results are in good agreement with the measured results.

Abstract:In this paper, the as-cast AZ31B magnesium alloy after homogenization treatment was taken as the research object, and a Gleeble thermal simulation compression test with deformation temperature of 200~450℃ and strain rate of 0.01~10s-1 was carried out on the Gleeble-3500 thermal simulator. The critical crack strain in the process of thermal compression was determined by high speed photographic technique, and the critical crack damage value was determined by FEM simulation. The results revealed that the classical Freudenthal criterion could well reflect the phenomenon of surface crack initiation and propagation observed by high-speed photographic technique and thermal simulation compression experiment, and the results are consistent with the metallographic observation. Therefore, based on the Freudenthal criterion, a new fracture criterion was established by introducing the Zener-hollomon factor to characterize the effect of deformation temperature and strain rate to the critical fracture damage of magnesium alloy during thermal deformation process. The fracture criterion well indicated the relationship between the critical fracture damage value of magnesium alloy and the stress state, strain, deformation temperature and strain rate, which provided a theoretical support for predicting thermal deformation cracking of as-cast AZ31B magnesium alloy and laid the technical foundation for optimizing the parameters of thermal processing of the alloy.

Abstract:Mg-10Y-2.45Znand Mg-10Y-2.45Zn-1Ca-0.37Al alloys were fabricated by magnetic levitation induction smelting coupled with copper-mould suction casting technique. The compound effect of high content Ca and small amount of Al alloying element addition on the formation of LPSO phase in as-cast Mg-10Y-2.45Zn alloy and the microstructure evolution and mechanical behavior under high temperature and high stress were investigated. The results showed that high content of Ca and a small amount of Al were involved in the formation of massive 18R LPSO and a large number of 18R LPSO phase delamination interface emerged under the as-cast condition. At high temperature, unlike the Mg-10Y-2.45Zn alloy, a large number of 18R LPSO phases dissolved and grew at the grain boundaries of Mg-10Y-2.45Zn-1Ca-0.37Al, the size of α-Mg grains coarsen. At high temperature and high plastic deformation, massive 18R LPSO kinked, delamination or crushed, dynamic recrystallization occured at the vicinity of the 18R LPSO phase boundary and a large number of fine rod-like 14H LPSO phases precipitatied in α-Mg matrix conspire to strengthen the alloy.

Abstract:The dynamic deformation behavior and mechanical constitutive of LZ91 magnesium alloy were investigated under high speed impacting using optical microscopy and X-Ray diffraction combing with Schmid factor. The results show that the flow stresses are not sensitive to strain rate and the Portevin-LeChatelier effect occurs. The fine α-Mg phase uniformly distributes in β-Li phase, causing that the dislocation motions are hindered. This finally induces that the adiabatic shear sensitivity decreases and the adiabatic shear band only occurs above 3600s-1. The special texture, which deviates the basal texture nearly 20-30°, in α-Mg phase forms, due to the Burgers orientation relationship between α/β phase interface. Twinning is not required to accommodate the uniform plastic deformation in α-Mg phase because of this orientation relationship. The Johnson-Cook (J-C) mechanical constitutive was modified and the fitting results well match with the experimental results.

Abstract:The second phase in Mg-Zn-Y alloy was successfully extracted by electrochemical phase separation, and the solid solution amount of alloy elements in Mg-Zn-Y alloy was obtained. A method for direct determination of solid solution in magnesium alloy was established. The activity and activity interaction coefficients of Zn in Mg-Zn-Y ternary alloy were calculated by using Miedema mixed enthalpy model and Toop model (symmetry) and Kohler model (asymmetric). The experimental measurements and calculations show that the interaction coefficients of Zn and Y in Mg-Zn-Y alloy are positive, which shows that Zn and Zn, Zn and Y are mutually exclusive in this system. The existence of Y can improve the activity of Zn, that is, the increase of Y solution will lead to the decrease of the solid solution amount of Zn. Thus, the supercooled degree of the liquid phase in the front of the solid-liquid interface is increased, so that the grain is refined, and the Mg₃Y₂Zn₃ eutectic phase of the grain boundary is increased and the mesh is gradually continuous.

Abstract:The temperature distribution of the AZ31 magnesium alloy in the rolling deformation zone was analyzed by numerical simulation. The empirical formula of the average temperature of the magnesium plate after rolling with respect to the roll temperature, the rolling velocities, the rolling reduction rate, and the thickness of the plate was established and supplemented with corresponding experiments. verification. The results show that when the magnesium plate is thin and the rolling velocity is small, the plastic deformation heat of the center layer of the magnesium plate is transferred to the surface in the rolling deformation zone. The temperature rise of the center layer cannot represent the temperature rise caused by the deformation of the magnesium plate. The average temperature of the magnesium plate after rolling is positively related to the roll temperature, rolling velocity and rolling reduction rate, and inversely related to the sheet thickness. The maximum relative error between the calculated and experimental values of the formula is 8.34%, and the average relative error is 7.4%. The formula can well predict the average temperature of the magnesium plate after rolling. The proposed empirical formula for magnesium plate temperature prediction is conducive to the realization of "isothermal rolling" control of AZ31 magnesium alloy sheet; it is of guiding significance for the reasonable formulation of magnesium alloy rolling process system and the selection of subsequent rolling equipment

Abstract:It is significant to investigate the effect of La2O3 as milling aid and hydrogen sorption catalyst for magnesium in order to solve its problem of low kinetic performance. The XRD analysis shows that after milling with 1.0 mol.% of La2O3, the crystallite size of Mg decreases to 49.7 nm, while it is 51.6 nm without La2O3. The decrease in crystallite size from the addition of La2O3 is in favor of the improvement of hydrogen sorption rate of Mg. The SEM observation shows that La2O3 nanocryatallites contact with crystalline Mg closely and form mosaic structure, which is in favor of La2O3 playing the role of catalysis for hydrogen sorption of Mg. The kinetics test shows that with the addition of La2O3, the hydrogen sorption rate of Mg increases obviuosly. With the addition of La2O3, the activated energy of hydrogen absorption decreases by 49.8 kJ/mol, and the activated energy of hydrogen desorption decreases by 23.1 kJ/mol. So, the kinetic performance of hydrogen sorption of Mg is substantially improved with the addition of La2O3. The p-c-T isothermal absorption analysis shows that the hydrogen absorption activity of Mg increases and results in lower equilibrium hydrogen pressure. The DSC analysis shows that the hydrogen desorption rate of MgH2 decreases with the addition of La2O3. In the process of milling, nanoscale La2O3 play the role of milling aid with its higher hardness than that of Mg, and it does not react with Mg; in the process of hydrogenation and dehydrogenation, La2O3 plays the role of catalyst, and it does not react with H2.

Abstract:The Mg-3Zn-1Y-0.6Zr-0.5Ca bio-magnesium alloy was prepared by conventional casting method. The effect of the microstructures and mechanical properties of alloys extruded at different extrusion speeds (10, 30, 60 and 90 mm / min) was investigated. Results show that the size of dynamic recrystallization grains increases and the area of non-dynamic recrystallization decreases with increasing the extrusion speeds. Extrusion speeds affect the morphology and distribution of the precipitation, which affects the occurrence of dynamic recrystallization in turn. Texture decreases with increasing the extrusion speed. As the extrusion speed increases, the ductility of the alloy increases but the tensile strength decreases. The alloys exhibits excellent comprehensive performance, whose tensile strength and elongation are 270Mpa and 19.6% when the extrusion speed is 60mm/min.

Abstract:Stir casting was employed to fabricate three kinds of magnesium matrix composites, which is 5μm10vol%Grp/AZ91、(5μm5vol%Grp+5μm5vol%SiCp)/AZ91 and (5μm5vol%Grp+10μm5vol%SiCp)/AZ91 respectively. Subsequently the composites was subjected to hot extrusion at 300℃ with ram speed of 0.03mm/s. And the effect of SiCp on microstructures、mechanical properties and wear resistance was studied. The results showed that the grain size of composites increase and the phenomenon of fragmentation of graphite among the three composites became more remarkable along with the adding and increasing size of SiCp. Extruded 5μm10vol%Grp/AZ91 composite possesses poor tensile strength、hardness and plasticity which was all improved after mixing 5μm SiCp, and the mechanical properties was further enhanced by increasing the SiCp size from 5μm to 10μm. And the wear rate of 5μm10vol%Grp/AZ91 composite was decreased along with the adding and elevated size of SiCp. On the contrary, the friction coefficient was significantly increased by enlarging the SiCp size. The dominant wear mechanisms of 5μm10vol%Grp/AZ91 composite was delamination wear which totally turn into abrasive wear in 10μmSiCp hybrid reinforced composites by increasing the size of SiCp.

Abstract:Abstract: The phase constitution, tensile properties and failure mechanism during tensile process of as-cast, as-solutioned and as-aged samples of a Mg-6Al-6Zn-3Sn-1Y-0.5Mn (AZTYM66310) magnesium alloy are investigated. The α-Mg primaries in the microstructure of as-cast AZTYM66310 alloy appear typical equiaxed dendrites morphology, and a large number of interdendritic phases formed during solidification, including Mg + Mg32 (Al, Zn) 49 eutectic, Mg2Sn divorced eutectic phases, Al2Y phases and Al8Mn4Y phases. After the solution treatment of 380℃ × 6h, the majority of Mg32(Al, Zn)49 phases and part of Mg2Sn phases were dissolved into the matrix, contributing the contents of Al, Zn and Sn in the matrix increasing significantly, while Al2Y phase and Al8Mn4Y phase not changing significantly. Solution treatment significantly improves the tensile strength and the elongation of the alloy. After aging treatment of 380 ℃ × 6h + 150 ℃ × 16h, a large number of nano-scaled particle reinforced phases precipitated in the alloy, especially near the grain boundary, contributing to the yield strength increasing to 187.4 MPa. During the tensile process of the alloy, the second phases in the structure first break or separate from the matrix, resulting in the generation of microcracks. And then these microcracks propagate along the grain boundaries, eventually causing the sample to fracture.

Abstract:The chitosan interlayer was formed on ultrasonic micro-arc oxidation(UMAO) coating of pure magnesium by electrophoretic deposition technique, on which we employed immersion method to make coatings with chinese herbal extract. Influence of chinese herbal extract on microstructure, tribological properties, corrosion resistance and biological activity of the composite coatings was investigated. The results show that UMAO coating is sealed by coatings with chinese herbal extract. The corrosion resistance of the coatings with chinese herbal extract is increased with appropriate surface condition. The binding force and tribological properties of the coating with chinese herbal extract are increased under chemical binding. The coatings with chinese herbal extract also has shown better biological activity invitro.

Abstract:The uniaxial hot compression tests of casting Mg-2.5Sn (wt.%) and Mg-2.5Sn-0.2Y (wt.%) alloys were conducted on an MTS-CMT5I05 universal testing machine at temperatures ranging between 250~400℃ and the strain rate of 10_-4~10_-1 s_-1 with strain of 40%. The effect of yttrium (Y) addition content (0.2 wt.%) on the hot compression behavior of the casting Mg-Sn alloys were investigated by true stress-strain curves, peak stress, microstructures, constitutive equation, and DMM processing maps. Results showed that the Y addition increased the peak stress of 30% at low strain rate, but made any sense at high strain rate. Deformation mechanism was changed from the lattice diffusion to dislocation slip and climb. In addition, Y retarded the dynamic recrystallization, reduced the efficiency of power dissipation and expanded the flow instability area.

Abstract:Inthis article, firstly, the background of magnesium alloys semi-solid forming is briefly introduced,and then the present status of magnesium alloy semi-solid forming technology is reviewed from the four fields, including alloy designing, semi-solid forming technology, semi-solid forming under external field treatment and semi-solid simulation of Mg alloy. then,in the past decades of research results: magnesium alloy corrosion resistance increase, obvious grain size, size is more uniform, the preparation of the fine equiaxial recrystallizationorganization of semi-solid slurry, obtain better mechanical properties, to forecast the product defects, implements the process optimization. The semi-solid process of magnesium alloy is further improved and innovated, which is of great significance to the development of magnesium alloy, Finally, the future development direction of semi-solid forming of magnesium alloys is prospected.

Abstract:We fabricated the flexible transparent conductive films composed of silver nanowires (AgNWs) and reduced graphene oxide (rGO) as hybrid transparent electrode and mixed cellulose eater (MCE) as substrate by vacuum-filtrating method. Effect of rGO on the electrical and optical and mechanical properties of flexible transparent films composed of rGO and AgNWs were studied. The results show that with rGO deposition density increase, the optical transmission at 550 nm has a little decrease, while the sheet resistance (Rs) gradually decrease. Tape tests up to 200 cycles and bending fatigue tests up to 200 cycles were performed by monitoring the in-situ resistance change. Film sustained excellent reliability of the AgNWs/rGO hybrid conductive networks, where the fractional resistance change is little overt increase after tape tests and less than 3% after bending test. The excellent mechanical properties of the AgNWs/rGO film can be attributed to the burying of the AgNWs and RGO film at the surface of MCEs.

Abstract:The site occupancies and antisite defects play important role in the physical and mechanical properties of intermetallic compound alloys. In this paper, the effects of Al concentration (c_Al) and temperature (T) on the change trend of site occupancies and antisite defects in B2-FeAl, which has attractive properties, are investigated by phase field method. The numerical results show that the increase of c_Al or the decrease of T can result in an acceleration of solute atoms segregation in matrix phase, and make site occupancies of Al and Fe as well as antisite Fe/Al reach equilibrium state earlier. Meanwhile, the increase of c_Al or the decrease of T can enhance the site occupancies of Fe and Al and reduce the two types of antisite defects. Furthermore, the theoretical results show that the change of c_Al and T is not able to change the main type of antisite defect in B2-FeAl ordered phase.

Abstract:Zirconium dioxide (ZrO₂) nanoparticles were synthesized by electrical explosion of zirconium wire in the air. The process of wire explosion and particles formation were analyzed according to the measured current, voltage and calculated deposited energy waveforms. It was found that electrical breakdown through the vapor of Zirconium wire and the surrounding air resulted in an explosion and stopped the energy deposition in wire. By scanning electron microscopy (SEM) and transmission electron microscope (TEM) of the products, it was found that the morphologies of synthesized nanoparticles were nearly spherical and the diameters range from 30.6 to 69.4 nanometers. The x-ray diffraction (XRD) analysis show that the powders consist of monoclinic ZrO₂ (m- ZrO₂) and tetragonal ZrO₂ (t- ZrO₂), the content of t-ZrO₂ increases while the content of m-ZrO₂ decreases with the increased charging voltage, the average sizes of the m-ZrO₂ and t-ZrO₂ are both increase when the charging voltage increases.

Abstract:Based on the CALPHAD approach and vacuum arc melting technology, the Cu_x(Fe_0.64Ni_0.32Co_0.04)_100-x(x=30, 45, 60, wt. %) series alloys were designed and prepared. The effects of annealing process on microstructures, thermal conductivity (TC) and thermal expansion coefficients (CTE) were investigated in these prepared alloys. The result shows that the Cu-Fe₆₄Ni₃₂Co₄ isotropic polycrystalline alloys present two separate fcc phases (fcc Cu-rich phase and fcc (Fe, Ni, Co)-rich phase) microstructures after annealing at 600 °C and 800 °C. After annealing at 600 °C for 50 h, the CTE of the alloys ranged from 6.88 to 12.36×10_-6 K_-1. And TC varied from 22.91 to 56.13 W.m_-1.K_-1. Particularly, the TC are significantly higher than that of Invar alloy, and the CTE of Cu₃₀(Fe_0.64Ni_0.32Co_0.04)₇₀ and Cu₄₅(Fe_0.64Ni_0.32Co_0.04)₅₅ alloys can well match with that of semiconductor in electronic packaging.

Abstract:In the forming process of automotive aluminum alloy, springback is one of the main defects and difficult to be controlled. In this study, stress-strain curves of automotive aluminum alloy 6061 are obtained through tensile tests at room temperature and the constitutive model is established based on a modified Johnson-Cook equation. The model is used in finite element simulation of V-bending tests to investigate the effect of different anisotropic yield criterions on accuracy of springback prediction. Experimental and simulation results indicate that the prediction results are more accurate when YLD2000-2d yield criterion is applied and the efficacy of the model in sprignback analysis is verified. Furthermore, the effect of several different factors on springback behavior of aluminum alloy sheet was investigated, including deformation degree, drawing velocity, friction condition and blank holding force. The experimental and numerical investigation is applied in stamping forming process of aluminum alloy inner panel of engine cover and the springback is reduced effectively.

Abstract:The main technical problem in the preparation of hypereutectic Al-high Si alloy is the refinement of the primary Si particles. In this paper, a new method for the preparation of Al-high Si alloy with refined primary Si particles by filtration treatment is proposed. During this process, the melt of hypereutectic Al-Si alloy underwent the filtration treatment at the temperature of little above the eutectic line in the Al-Si binary phase diagram. After that, the large-sized primary Si particles were retained by the filter screen, while the small-size primary Si particles together with the eutectic melt went through the screen and cooled down, forming into the hypereutectic Al-high Si alloy products. The Si content in the Al-high Si alloy prepared in this study was about 27 wt.%, the average diameter of the primary Si particles reached less than 45 μm, the roundness of the primary silicon particles was 1.43, and the brinell hardness of the alloy was about 70 HB. By this method, it is expected to obtain the Al-high Si alloy with higher degree of sphericity of the primary Si particles and higher Si content.

Abstract:Perovskite is the inevitable phase formed in the cathode during electrolysis of TiO₂ in molten CaCl₂ by FFC Cambridge process. Dependency of perovskite in the cathode on gases released from the anode in the process of the preparation of titanium is studied. The results show that three stages is obtained based on the phases formed in the cathode including formation of perovskite, deoxygenation from perovskite and titanium suboxides to TiO and deoxygenation from TiO to Ti . Perovskite formed in the cathode is close related with gases released from the anode although the decomposition voltage is lower than that of CaCl₂. Chlorine releases from the anode due to overvoltage which is caused by the formation of perovskite in a short time. Amount of chlorine is depended on the mass of TiO₂ and generation of different titanium suboxides during electrolysis process. The mass ratio of TiO₂ and chlorine is from 9:2 to 46:2 when titanium suboxides are between Ti₃O₅ and TiO at the first deoxygenantion stage. The anode is no obvious consumption during chlorine releases. Formation of the perovskite and deoxygenation of Ti₂O are the main limited step to prepare titanium by electrolysis process in molten CaCl₂. The total current efficency from TiO₂ to Ti is 24.07%. The current efficiency of the first stage is between 22.37% and 44.74% and the second stage is between 30.18% and 37.72%.

Abstract:The cold-rolled Cu/Al laminated composite was annealed at 475-525℃ for 1-8min, the temperature field of Cu/Al composite during annealing was simulated using finite element software, and the microstructures and properties of Cu/Al composite were investigated by scanning electron microscopy(SEM), energy dispersive X-ray spectrometry(EDS), X-ray diffractometer(XRD), electron back-scattered diffraction(EBSD) and microhardness tester. The results indicated that three intermetallic compounds (IMCs), CuAl<sub>2</sub> ,Cu<sub>9</sub>Al<sub>4</sub> and CuAl phases formed successively at the Cu/Al interface, complete recrystallization of both the Cu and Al matrix took place to form equixed grain, within the annealing process scope in which the thickness of IMCs layer is smaller than 4μm, the microhardness of Cu and Al matrix drops fast to approach that of annealing at 350℃ for 1h.Therefore, the high-temperature short-time annealing process could substitute for low-temperature long-time annealing process. Furthermore,the nucleation mechanism of primary phase was proposed and the kinetics of IMCs during high-temperature short-time was analytized and calculated, and an empirical numerical method was proposed to calculate the thickness of IMCs during the non-isothermal annealing process.

Abstract:Al_0.7Sb₂Te₃ternary target was prepared by vacuum synthesis and sintering-HIP method by mixed powder with atom ratios of 0.7:2:3 as raw material. Target properties was characterized by means of XRD, FESEM, EDS and XPS, and the state of Al in the ternary target was researched primarily by XPS. The results show that with Aluminum doped, main phase Sb₂Te₃’s lattice constant decreases, and the Aluminum dispersoids can coexist together with Al_0.1Sb₂Te₃ matrix, which mean the existence of effect on target organization structure with Aluminum doped; with etching depth increases from 0 to 405.9nm, the main content of Aluminum’s valence is gradually transferred from the compound state of Al₂O₃ to simple substance state, and the area depth of Aluminum’s form dominated by Al₂O₃ is about 90nm; with etched by 405.9nm, the Aluminum’s valence from non-oxide and Antimony’s valence from AlSb can certify the Aluminum of Al_0.1Sb₂Te₃ matrix influences target organization structure by forming effectively AlSb.

Abstract:In this paper, the electronic structures and optical properties of two-dimensional carbonaceous graphene, graphdiyne are studied based on density functional theory (DFT). The results reveal that the graphene is more stable than the graphdiyne. In the vicinity of Fermi level, the electronic states of grapheme and graphdiyne are mainly contributed by the C-2p state. The graphene exhibited better non-linear optical absorption properties and electrical conductivity under the visible light conditions. However, graphdiyne has excellent optical absorption and electrical conductivity in the range of partial infrared light. In addition to the transition from valence-band to conduction-band, there is also the inner-band transition near the Fermi level. The conclusion can provide theoretical basis for the application of two-dimensional carbon material grapheme and graphdiyne in optoelectronic devices and photocatalysi.

Abstract:Based on the experimental results and analysis of grain size and content of soft magnetic phase in Nd₂Fe₁₄B/α-Fe permanent magnetic material,simple models were established to give a further evidence and relatively accurate result of grain size and content of soft magnetic phase in two-phase nanometer composite permanent magnetic materials. The comprehensive analysis shows, when obtain the optimal magnetic of Nd₂Fe₁₄B/α-Fe permanent magnetic material, the size of soft magnetic phase ~ 8 nm, and the content ~ 40%. The data lay a foundation in theory for the requirement of grain size and phase content to obtain the optimal magnetic of two-phase nanometer composite permanent magnetic materials, FePt / Fe₃O₄ and Sm₂Fe₁₇N₃/α-Fe for example.

Abstract:Near-equiaxed fine grains with the average grain size of 1.21 μm of pure tungsten has been fabricated via high pressure torsion (HPT) at the temperature of 550 ℃, under a pressure of 1.5 GPa. The influence of HPT processing at various turning numbers on microstructure and micro-mechanical properties of sintered commercial pure tungsten has been investigated by means of EBSD and nano-indentation experiments. It was found that the pores in material were closed effectively, the grains were refined significantly and the ratio of high angle boundary increased rapidly after HPT processing. Moreover, when the strain was relatively low (at the turning number of 1), there was a preferred grain orientation along <101>, which weakened to disappearing with the strain increasing; when the strain was high (at the turning number of 5), some small dynamic recrystallites generated at grain boundary. In addition, the nanohardness and yield strength increase obviously as the strain increasing, which is due to pores closure, grain refinement, lattice distortion, dislocation density increase and high angle grain boundary formation; the combination of relative density, residual stress and high density dislocation, make the elastic modulus of HPT-processed samples higher than sintered commercial pure tungsten, but decrease slightly as the strain increasing during the processing.

Abstract:This work studied the effect of oxygen vacancies in the Bi2O22+ and CO32- layers on the crystal structures, electronic and optical properties of Bi2O2CO3 with density functional theory (DFT) methods. The cell parameters and Bi-O bond lengths of Bi2O2CO3 before and after the introduction of oxygen vacancies were similar, so the effect of oxygen vacancies on crystal structures could be ignored. However, oxygen vacancies as electron doner provided electrons for the surrounding atoms, resulting in the change of charge distributions after the introduction of oxygen vacancies. Moreover, oxygen vacancies could reduce the band gap of Bi2O2CO3 and enhance the adsorption of visible light. This effect of oxygen vacancies became more obvious with the increasing of oxygen vacancy concentration. It was notable that the effects of oxygen vacancies in the Bi2O22+ and CO32- layers were different. Once a oxygen vacancy was introduced in the CO32- layer, a defect level appeared within the band gap of Bi2O2CO3. The oxygen vacancies in the Bi2O22+ layer were more easily formed in Bi2O2CO3 than that in the CO32- layer. Further more, the functions of oxygen vacancies in the Bi2O22+ layer for the reduction of band gap and the enhancement of visible light adsorption were more effective than that the oxygen vacancies in the CO32- layer, which was more obvious with the increasing of oxygen vacancy concentration. When the concentration of oxygen vacancies in the Bi2O22+ layer reached to 6.25%, the photoelectric properties of Bi2O2CO3 were the best. The DFT calculation results are consistent with the previous experimental results, and could provide insights into the mechanism for promoting the photoelectric properties of Bi2O2CO3 and other bismuth-based materials.

Abstract:For metal droplet deposition increases material manufacture metal flow in the intermittent random change, intermittent morphology parameters, such as difficult to control and forecast of the existing problems, the method of combining the theoretical analysis and experimental study of metal flow discontinuous intermittent morphology and its influencing factors in the process of pulse pressure, pulse frequency are studied, reveals the discontinuous morphology length distribution. Results show that by adjusting the pulse pressure and pulse frequency, and can improve the metal flow of fracture shape accuracy and dimensional accuracy, can provide stability for the subsequent manufacturing process of uniform micro drip.

Abstract:In this paper, activated carbon, mesoporous carbon, carbon nanotubes and graphene were used as catalyst carriers, CeO2 was added as cocatalyst, and five groups of catalysts were prepared by microwave-assisted glycol reduction of chloroplatinic acid. X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron energy spectrum (EDAX), specific surface area and pore size analyzer (BET), and X-ray photoelectron spectroscopy (XPS) were used to characterize the microstructure of CeO2 and catalysts. The electrochemical performance of the catalysts was tested by electrochemical workstation. The results showed that the catalyst synthesized with graphene as the carrier and CeO2 as the co-catalyst have the best activity, stability and resistance to poisoning for the catalytic oxidation of ethanol. The electrochemical active area is 86.83 m2/g, the peak current density value is 751.03 A/g, the activation energy for the catalytic oxidation of ethanol is the lowest and the steady state current density at 1100s is 67.33 A/g.

Abstract:_:_{Silver nanowires have garnered a significant amount of research attention due to their excellent electrical, transmittance, flexible properties as well as the source of raw materials is wide and cheap, which are now regarded as the next generation of flexible transparent materials} _{and have been used in the fields of solar cells, organic light-emitting diodes (OLEDs) and flexible liquid crystal displays (LCDs). The length and yield of silver nanowires synthesisd with traditional polyol process is lower, which is the major method for the synthesis of silver nanowires. For above background, to improve the length and yiled of silver nanowires, CuCl}₂_{was used as the etching agent, which can prevent the oxidative etching, besides, temperature, polymer to AgNO}₃_{ratio and CuCl}₂_{amount were all considerable factors. The result show that the length of silver nanowires could grow to 60 μm when temperature was 160}_℃_{, PVP to AgNO}₃_{molar ratio was 1.5, AgNO}₃_{to CuCl}₂_{molar ratio was 200, the yield of silver nanowires could over 80%.}

Abstract:The microstructure evolution and mechanical properties of powder metallurgy FGH96 alloy under different solution heat treatment conditions were analyzed by means of electronic probes, field emission scanning electron microscopy and other advanced detection methods. Results showed that the edge part of the powder metallurgy FGH96 alloy turbine disk was analyzed by electron probe. It was found that the bright white granular boride phase was observed, and the surface of the control element was scanned. It can be determined that the boride phase is mainly rich in elements W and Mo. As the solution temperature increased from 1080 °C to 1160 °C, both tensile strength and yield strength increased slightly, while tensile strength and yield strength increased with increasing cooling rate; FGH96 alloy after treatment with different solution temperature The creep performance is comparable, and as the cooling rate increases, the creep resistance is greatly increased. Through the research on the microstructure and mechanical properties of FGH96 alloy.

Abstract:Al-Li alloy is widely used in the aerospace field, due to its high specific strength and high specific modulus. The processing of 2198 alloy is investigated. 2198 alloy sheet with excellent mechanical properties is successfully manufactured. It will help the industrial production of 2198 Al-Li alloy. The ingot is melted and cast in vacuum induction melting (VIM) furnace. During the followed homogenization the as-cast microstructure can be completely vanished. The ingot is rolled to sheet with 2mm thickness, via multi-pass hot-rolling. Then, the solution, water quenching, pre-deformation, naturally aging and artificial aging are respectively carried out. The tensile strength of final 2198 Al-Li alloy sheet in the rolling direction is 486MPa. The precipitate T1 generated in the artificial aging can not only increase the strength obviously, but also decrease the anisotropy of 2198 Al-Li alloy sheet.

Abstract:The La3+/ZnO photocatalytic film catalyst was prepared by sol-gel method with zinc acetate as zinc source. The samples were characterized by XRD, SEM, XPS and UV-vis. The photocatalytic properties of thin film catalyst under UV light were investigated with sulfamethazine as the target decomposition. The results showed that lanthanum as trivalent positive ions exists in the film, and lanthanum was successfully mixed into ZnO crystal lattice; lanthanum doping reduced the gap width of the catalyst, the crystal particles decreased, and the specific surface area increased; The surface of thin film catalyst was uniform; Lanthanum doped ZnO films had a higher catalytic efficiency for antibiotics. This work will bring about potential application in treatment of antibiotic pollutant

Abstract:In order to improve the working performance of the gas deflector of aircraft carrier, the ablation test intended for simulating the takeoff condition is conducted by placing the test specimens of C/C-SiC composite in the wake flow of carrier-based aircraft so as to measure the ablative rate of the test specimens. The ablation mechanism and thermal shock damage of the test specimens are analyzed by adopting a scanning electron microscope (SEM) and micro-CT to observe the micro structure of the test specimens after ablated. By using energy dispersive spectrometry (EDS), the components of combustion products are measured to analyze the ablation mechanism and thermal shock damage of the test specimens. According to the result, the linear ablative rate of the test specimen is about 0.0405mm/s and its mass and its mass ablative rate is about 0.0349g/s. The heat affected zone experiences matrix crack and unapparent oxidation reaction. In the transition zone, the SiO2 produced by the reaction is precipitated around the carbon fibers and forms a sheathing structure, thus effectively retarding oxidation reaction from transferring inward and reducing the ablative rate of the test specimen. In the center of ablation, the retardation of SiC on oxidation reaction is small and the test specimen forms a concave pit, with carbon fibers being distributed in the shape of pointed bamboo shoots. On the whole, the material gives its outstanding anti-ablative performance.

Abstract:Alumina matrix composites reinforced by carbon fiber cloth preform with a lamination and stitching structure (C/Al₂O₃) and fabricated by sol infiltration and heat treatment route were selected as raw materials in this paper. The solid particle erosion behavior of C/Al₂O₃ composites was investigated using corundum powders as medium, and the friction and wear properties were studied according to national standard GB5763-2008. At room temperature, erosion rate is augmented with increasing impact angle and feeding rate of corundum powders. The remarkably enhanced erosion rates are observed at high temperatures due to the combination of mechanical impact and thermal shock. C/Al₂O₃ composites exhibit stable friction factor and very low wear rate under the conditions regulated by national standard GB5763-2008. The erosion and wear mechanisms are discussed based on the evolution of microstructure. Profiting from the reinforcing and toughening mechanism of continuous carbon fiber, C/Al2O3 composites present non-catastrophic fracture behavior and better security in service than monolithic Al2O3 ceramics even if the matrix density of C/Al2O3 composites was inferior to monolithic Al2O3 ceramics.

Abstract:Abstract: In order to prevent the luminescence quenching of rare earth phosphor in composite coatings, the sol-gel method was used to preparate SiO2-SrAl2O4:Eu2+,Dy3+ coated powders. The Cu-14Al-X/SrAl2O4 composite coatings were preparated on the 45 steel substrate by cold spray technology, and the friction and wear condition of the coatings were monitored by luminescence.The SiO2-SrAl2O4 powder was characterized by SEM and laser particle size analysis, combined with EDS and F97 Pro fluorescence spectrophotometer ,to study and detect coating’s microstructure, microcomponent and luminescence properties. The luminescence quenching mechanism of phosphor powder and SiO2 coating process effect of anti quenching in cold spray process were explored. The results show that contacting between rare earth phosphor and Fe, Mn, Ni elements and high speed impact of spray particles on each other are the main causes of the luminescence quenching of the cold spray coating. The preparation of SiO2-SrAl2O4 coating powder can be realized by sol-gel method, which can form the SiO2 shell structure that could optimize the surface morphology of the powder，make the powder smoothly and roundly, improve the powder’s hardness, have a good microstracture transition, get a better light-emitting property.

Abstract:Effect of binary basicity and La2O3 content on the behavior of lanthanum-rich aluminum-containing CaO-SiO2-Al2O3-MgO slag briquets self-reduction have been researched. The blast furnace slags and aluminite powder were pressed into Φ15mm cylindrical pieces after mixing. The lanthanum-rich aluminum-containing slag briquets self-reduction experiments were proceed in the medium-frequency induction furnace. The specimens were collected online at different time and soluted the specimens by nitrohydrochloric acid. The non-metallic secondary phases were separated from iron matix by non-aqueous electrolytic process and soluted by nitrohydrochloric acid. The quantitative analysis of lanthanum which was in the iron and non-metallic secondary phases by inductively coupled plasma source mass spectrometer (ICP-MS). The content of La alloying in the iron was acquired by amount of lanthanum in the iron subtracting lanthanum in the non-metallic secondary phases. The slag activity model has been established according to the theory of moleculars-ions coexistence and the activities of La2O3 in different slags have been calculated. The results indicated that, increasing the binary basicity from 1.05 to 3 led to decreas-ing the activity of the La2O3 of the slag and lower La2O3 reduction amounts in the slag briques from 2.15ppm to 0.42ppm. The recovery radio of lanthanum was decreasing from 13.72% to 2.93%. The activity of the La2O3 of the slag and the La2O3 reduction amounts was increased from 2.15ppm to 10.94ppm with the increase of the La2O3 content from 0.15% to 1% in the slags. The recovery radio of lanthanum was decreasing from 13.72% to 6.68%.

Abstract:In this paper, ordered porous strontium ferrite (SrFe12O19) thin films were prepared by dip-drawing method using polystyrene (PS) spheres template. The PS template was orderly assembled on clean silicon substrate through PS sphere emulsion, which was synthesized by microemulsion polymerization. The porous SrFe12O19 thin films were fabricated by filling the SrFe12O19 precursor sol prepared by sol-gel method on the interspaces among adjacent PS spheres in the PS template, and then removing the PS spheres by heating at 900 °C for 2 h. The effects of PVP content on the microstructure of PS spheres and the drawing time on the microstructure of PS template and the porous SrFe12O19 thin films were investigated. Then the formation mechanism of porous SrFe12O19 thin films was discussed, and the corresponding model was established. The results show that PS spheres with uniform particle size could be obtained by adding 0.2 g PVP, and the interspaces between the microspheres were obvious; the single layer ordered PS template could be obtained by immersing the silicon substrate in the PS sphere emulsion for 10 s. The pure SrFe12O19 porous thin film with honeycomb structure and a pore diameter of about 200 nm can be prepared by immersing PS template in the SrFe12O19 precursor sol for 10 s, and it shows the excellent hard magnetic properties: saturation magnetization of 27.9 emu/g, remanence of 15.5 emu/g and coercivity of 2613.4 Oe.

Abstract:In order to improve the bioactivity of tantalum, NaOH solution was applied to tantalum, and the optimal concentration of alkali treatment was explored by simulating somatic fluid (SBF) soaking experiment. Alkali-treated tantalum was pre-calcified in CaCl2 solution and K2HPO4 solution, respectively. Tantalum after 0.7mol/L alkali treatment, soaked in SBF for 2 weeks, the surface can be covered with hydroxyapatite. After pre-calcification, tantalum soaked in SBF for 4 days, the surface can be covered with a layer of hydroxyapatite, indicating that pre-calcification substantially increase the bioactivity of tantalum. The mechanism is pre-calcification can make the sample surface quickly complete the nucleation of calcium and phosphorus compounds, immersed in SBF hydroxyapatite can grow rapidly.

Abstract:Low-resistivity ITO nanocubes were successfully prepared in one step by the solvothermal method. The microstructure and electrical properties of ITO nanoparticles can be adjusted by changing solvents, reaction temperature and reaction time. The results show that the lowest electrical resistivity and the average size of ITO nanoparticles was 0.2 Ω×cm and 45.95 nm respectively when the reaction temperature and time were 250 ℃ and 24 h respectively with ethylene acohol as solvent. As reaction time was prolonged, the rod-like indium hydroxides were transformed to cubic In2O3 nanoparticles gradually through the dissolution-recrystallisation mechanism. During the formation of In2O3 nanocrystals, the growth rate perpendicular to (200) plane reduced, caused by the adsorption of glycol and tetramethyl ammonium ion on the surface of particles, which induced the formation of cubic-shaped ITO nanoparticles.

Abstract:Using surface-modified cast tungsten carbide particles (CTC_P) as reinforcement, NiCrBSi alloy as binder phase and refractory steel as substrate, refractory steel matrix composite reinforced by zoning CTC_P/NiCrBSi was prepared by vacuum fusion sintering. Composite interface was observed and formation mechanism of composite interface was analyzed. Wear behaviors of the composite in the range of 25~800℃ were studied. Wear mechanisms of the composite were also discussed. The results showed that, theSstructure is compact and the CTC_P are evenly distributed in CTC_P/NiCrBSi area of composite; the interface between CTC_P/NiCrBSi area and refractory steel substrate is composed of three parts: CTC_P dissolution zone, γ-Ni isothermal-solidification zone and element spread influence zone rich in (Fe,Cr)-B; within the test temperature range, the wear rate of composite is less than that of refractory steel and both the wear rate and the relative wear resistance of the composite show the trend of decreasing and then increasing with the increase of the test temperature; the relative wear resistance of composite at 800℃ is the highest, reaching 1.8 times that of refractory steel; in the range of 25~600℃, the wear mechanisms of the composite are mainly micro-plowing, fatigue fracture induced by undergoing plastic deformation, CTC_P surface fatigue fracture caused by abrasive rolling and scratching, CTC_P broken or shedding due to insufficient NiCrBSi support; in the range of 600~800℃, the wear mechanism of composite are mainly micro-plowing and mutual promotion of oxidation and wear.

Abstract:The effect of W content on the tribological properties of CrWN coatings under dry friction and PAO lubrication conditions was investigated by scanning electron microscope, X-ray diffractometer, nano-indentation tester, 3D profile-meter, and reciprocating tribometer. It was shown that the microstructure of CrWN coatings prepared by ion beam assisted deposition is changed from dense columnar crystals to coarse columnar crystals and then fibrous crystals. The hardness is first increased and then decreased with the increase of W content, and the maximum hardness is obtained when the W content is 9.96 at.%. Under dry friction condition, the friction coefficients of CrWN coatings are decreased first and then almost unchanged with the increase of W content; however, under PAO oil lubrication condition, the friction coefficients of CrWN coatings are gradually decreased with the increase of W content. Under dry friction, the introduction of W into CrN coatings at a low content will aggravate the wear of CrN-coated samples and their counterpart balls; but the wear resistance of CrN-coated samples and their counterpart balls is obviously improved by doping W.

Abstract:The paper first teases out the pore design requirements of porous tungsten matrix materials (PTMM). Secondly, the preparation of PTMM as the main line is introduced, including the process of tungsten powder pretreatment and forming, tungsten compact sintering, copper infiltration and removal, porous tungsten HIP and cryogenic machining. Finally, the test methods of properties of PTMM are summarized. Tungsten powders plasma spheroidization, tungsten compact extrusion and injection moulding are the future for the dispenser cathodes matrix. Porous tungsten capsule-free HIP contributes to high-reliability and long-life of dispenser cathodes. Porous tungsten cryogenic machining, an advanced sustainable process, is capable of short process manufacturing for porous tungsten matrix of dispenser cathodes.