The results of the calculation of thermodynamic properties in liquid state for ternary Al-Ni-Zn alloys using the newest version of the general solution model for thermodynamic prediction are presented. Nine sections with different molar ratios of Ni to Zn, Zn to Al and Al to Ni were investigated in a temperature interval of 1800-2000 K. Partial and integral molar thermodynamic properties in liquid phase for the Al-Ni-Zn ternary system are determined and discussed.

In order to explore the influence of welding parameters and to investigate the Al alloy (AA) nugget formation process, a comprehensive model involving electrical-thermal-mechanical and metallurgical analysis was established to numerically display the resistance spot welding (RSW) process within multiple fields and understand the AA-RSW physics. A multi-disciplinary finite element method (FEM) framework and a empirical sub-model were built to analyze the affecting factors on weld nugget and the underlying nature of welding physics with dynamic simulation procedure. Specifically, a counter-intuitive phenomenon of the resistance time-variation caused by the transient inverse virtual variation (TIVV) effect was highlighted and analyzed on the basis of welding current and temperature distribution simulation. The empirical model describing the TIVV phenomenon was used for modifying the dynamic resistance simulation during the AA spot welding process. The numerical and experimental results show that the proposed multi-field FEM model agrees with the measured AA welding feature, and the modified dynamic resistance model captures the physics of nugget growth and the electrical-thermal behavior under varying welding current and fluctuating heat input.

The effect of flow passage length in the die cavity and extrusion wheel velocity on the shape of aluminum sheath during the continuous extrusion sheathing process was analyzed by using finite element methods based on software DEFORM 3D and experimentally validated. The results show that by increasing the flow passage length, the velocity of metal at the cross-section of sheath tends toward uniformity, the values of the bending angles of sheath gradually approach the ideal value of zero and the cross-section exhibits a better shape. The extrusion wheel velocity has negligible effects on the bending shape and cross-section of the sheath product when a long flow passage is used.

Updated version of local non-equilibrium diffusion model (LNDM) for rapid solidification of binary alloys was considered. The LNDM takes into account deviation from local equilibrium of solute concentration and solute flux fields in bulk liquid. The exact solutions for solute concentration and flux in bulk liquid were obtained using hyperbolic diffusion equations. The results show the transition from diffusion-limited to purely thermally controlled solidification with effective diffusion coefficient →0 and complete solute trapping K^LNDM(v)→1 at v→v_Db for any kind of solid-liquid interface kinetics. Critical parameter for diffusionless solidification and complete solute trapping is the diffusion speed in bulk liquid v_Db. Different models for solute trapping at the interface with different interface kinetic approaches were considered.

A three-dimensional (3-D) modified cellular automaton (MCA) method was developed for simulating the dendrite morphology of cubic system alloys. Two-dimensional (2-D) equations of growth velocities of the dendrite tip, interface curvature and anisotropy of the surface energy were extended to 3-D system in the model. Therefore, the model was able to describe the morphology evolution of 3-D dendrites. Then, the model was applied to simulate the mechanism of spacing adjustment for 3-D columnar dendrite growth, and the competitive growth of columnar dendrites with different preferred growth orientations under constant temperature gradient and pulling velocity. Directional solidification experiments of NH₄Cl-H₂O transparent alloy were performed. It was found that the simulated results compared well with the experimental results. Therefore, the model was reliable for simulating the 3-D dendrite growth of cubic system alloys.

Molecular dynamics (MD) simulations of monocrystalline copper (100) surface during nanomachining process were performed based on a new 3D simulation model. The material removal mechanism and system temperature distribution were discussed. The simulation results indicate that the system temperature distribution presents a roughly concentric shape, a steep temperature gradient is observed in diamond cutting tool, and the highest temperature is located in chip. Centrosymmetry parameter method was used to monitor defect structures. Dislocations and vacancies are the two principal types of defect structures. Residual defect structures impose a major change on the workpiece physical properties and machined surface quality. The defect structures in workpiece are temperature dependent. As the temperature increases, the dislocations are mainly mediated from the workpiece surface, while the others are dissociated into point defects. The relatively high cutting speed used in nanomachining results in less defect structures, beneficial to obtain highly machined surface quality.

The capability of the torsion extrusion (TE) process as a severe plastic deformation (SPD) method was compared with the conventional forward extrusion (FE) process. The TE and FE processes were successfully performed on AA1050 alloy samples at room temperature. To simulate the above mentioned processes, finite element analysis was carried out using the commercial elasto-plastic finite element analysis ABAQUS/Explicit Simulation. It is shown that load requirement for the TE process is lower than that for the FE process. The equivalent plastic strain calculated by the FEA proved that higher values of strain are imposed to the sample in the TE process. The strain distribution for the TE sample at the final stage of extrusion shows smoother strain gradient in comparison with the one produced by the FE process.

A non-linear continuum damage model was presented based on the irreversible thermodynamics framework developed by LEMAITRE and CHABOCHE. The proposed model was formulated by taking into account the influence of loading frequency on fatigue life. The parameters H and c are constants for frequency-independent materials, but functions of cyclic frequency for frequency-dependent materials. In addition, the expression of the model was discussed in detail at different stress ratios (R). Fatigue test data of AlZnMgCu1.5 aluminium alloy and AMg6N alloy were used to verify the proposed model. The results showed that the model possesses a good ability of predicting fatigue life at different loading frequencies and stress ratios.

The mass of high-speed trains can be reduced using the brake disk prepared with SiC network ceramic frame reinforced 6061 aluminum alloy composite (SiC_n/Al). The thermal and stress analyses of SiC_n/Al brake disk during emergency braking at a speed of 300 km/h considering airflow cooling were investigated using finite element (FE) and computational fluid dynamics (CFD) methods. All three modes of heat transfer (conduction, convection and radiation) were analyzed along with the design features of the brake assembly and their interfaces. The results suggested that the higher convection coefficients achieved with airflow cooling will not only reduce the maximum temperature in the braking but also reduce the thermal gradients, since heat will be removed faster from hotter parts of the disk. Airflow cooling should be effective to reduce the risk of hot spot formation and disc thermal distortion. The highest temperature after emergency braking was 461 °C and 359 °C without and with considering airflow cooling, respectively. The equivalent stress could reach 269 MPa and 164 MPa without and with considering airflow cooling, respectively. However, the maximum surface stress may exceed the material yield strength during an emergency braking, which may cause a plastic damage accumulation in a brake disk without cooling. The simulation results are consistent with the experimental results well.

The thermodynamics of interactions between various oxides (CaO, MgO, Al₂O₃ and Y₂O₃) and molten Ti and Ti alloys was investigated. The dissolution mechanism of oxides in molten Ti alloys was provided and the stability of oxides in molten Ti alloys was investigated and predicted by thermodynamic analysis. Interactions between oxides and Ti−Al melts were studied by oxide crucible melting experiments. By quantitative analysis, it is indicated that impurity contents in alloys are proportionally decreased with increasing the Al content in alloys and decreasing the melt temperature, which is in agreement with the results of the predicting thermodynamic stability.

Based on the statistical analysis of blocking effect arising from anisotropic growth, the anisotropic effect on the kinetics of solid-state transformation was investigated. The result shows that the blocking effect leads to the retardation of transformation and then a regular behavior of varying Avrami exponent. Following previous analytical model, the formulations of Avrami exponent and effective activation energy accounting for blocking effect were obtained. The anisotropic effect on the transformation depends on two factors, non-blocking factor γ and blocking scale k, which directly acts on the dimensionality of growth. The effective activation energy is not affected by the anisotropic effect. The evolution of anisotropic effect with the fraction transformed is taken into account, showing that the anisotropic effect is more severe at the middle stage of transformation.

The hot forging of large-scale P/M TiAl alloy billet deformation was investigated based on a joint application of Deform-3D-based numerical simulation and physical simulation techniques. The temperature dependence on the thermal and mechanical properties of the billet was considered and the optimum hot working temperature of packed TiAl alloy was 1150−   1200 °C. Based on the simulation, the material flow and thermo mechanical field variables, such as stress, strain, and temperature distribution were obtained and the relationships of load-displacement and load-time were figured out. To verify the validity of the simulation results, the experiments were also carried out in a forging plant, and a pancake with diameter of 150 mm was obtained exhibiting a regular shape.

The constitutive model was developed to describe the relationship among flow stress, strain, strain rate, and deformation temperature completely, based on the characteristics of flow stress curves for a new kind of metastable β Ti2448 titanium alloy from isothermal hot compression tests, in a wide range of temperatures (1023−1123 K) and strain rates (63−0.001 s⁻¹). During this process, the adopted hyperbolic sine function based on the unified viscoplasticity theory was used to model the flow behavior of alloy undergoing flow softening caused by dynamic recovery (DRV) at high strain rates (≥1 s⁻¹). The standard Avrami equation was adopted to represent the softening mechanism attributed to dynamic recrystallization (DRX) at low strain rates (<1 s⁻¹). Additionally, the material constants were determined by optimization strategy, which is a new method to solve the nonlinear constitutive equation. The stress-strain curves predicted by the developed constitutive model agree well with the experimental results, which confirms that the developed constitutive model can give an accurate estimate of the flow stress of Ti2448 titanium alloy and provide an effective method to model the flow behavior of metastable β titanium alloys during hot deformation.

Departing from the volume-averaging method, an overall solidification kinetic model for undercooled single-phase solid-solution alloys was developed to study the effect of back diffusion on the solidification kinetics. Application to rapid solidification of undercooled Ni−15%Cu (mole fraction) alloy shows that back diffusion effect has significant influence on the solidification ending temperature but possesses almost no effect on the volume fraction solidified during recalescence. Inconsistent with the widely accepted viewpoint of Herlach, solidification ends at a temperature between the predictions of Lever rule and Scheil’s equation, and the exact value is determined by the effect of back diffusion, the initial undercooling and the cooling rate.

In order to optimize technological parameters and realize directional solidification, temperature fields of cold crucible continuous melting and directional solidifying Ti50Al (mole fraction, %) at different parameters were calculated. Continuous casting of the model is achieved by distinguishing the moving unit at different positions. The calculation results show that the feeding rod is entirely melted at 200 s, the melt of feeding rod has some superheat degree at 300 s under the conditions of 52 kW and 3.0 mm/min. Both the superheat degree and the molten zone of the feeding rod reduce, the solid−liquid interface becomes concave with increasing velocity from 1.2 mm/min to 6.0 mm/min when the power is 52 kW, and the outside layer of the rod cannot be melted at the velocity of 6.0 mm/min. Both superheat degree and the molten zone of the feeding rod increase, the solid−liquid interface descends and becomes concave with increasing power from 48 to 58 kW at velocity of 3.0 mm/min, and the rod cannot be melted entirely when the power is 48 kW. Cold crucible continuous melting and directional solidification of TiAl alloys will be achieved successfully when the pulling velocity and the power are matched appropriately.

The first-principle calculations were performed to investigate the structural, mechanical, electronic and thermal properties of the binary ductile intermetallic compound CeAg with B2 (CsCl) structure. The calculated value of lattice constant a₀ for CeAg with generalized gradient approximation is 3.713 Å, which is in better agreement with experimental data than local spin density approximation. The negative energy of formation implies that CeAg with B2 structure is thermodynamically stable phase. The greater separation between the d bands of Ce and Ag results in weaker bond hybridization of Ce d-Ag d, which prevents formation of directional covalent bonding. The three independent elastic constants (C₁₁, C₁₂ and C₄₄) are derived and the bulk modulus, shear modulus, elastic modulus, anisotropy factor, and Poisson ratio are determined to be 57.6 GPa, 15.8 GPa, 43.4 GPa, 3.15 and 0.374, respectively. The elastic constants meet all the mechanical stability criteria. The value of Pugh’s criterion is 3.65. The ductility of CeAg is predicted if Pugh’s criterion is greater than 1.75. Furthermore, the variations of volume, bulk modulus, heat capacity, and thermal expansion coefficient with temperature and/or pressure were calculated and discussed.

The first-principles method based on the projector augmented wave method within the generalized gradient approximation was employed to calculate the superlattice intrinsic stacking fault (SISF) and complex stacking fault (CSF) energies of the binary Ni₃Al alloys with different Al contents and the ternary Ni₃Al intermetallic alloys with addition of alloying elements, such as Pd, Pt, Ti, Mo, Ta, W and Re. The results show that the energies of SISF and CSF increase significantly with increase of Al contents in Ni₃Al. Addition of Pd and Pt occupying the Ni sublattices does not change the SISF and CSF energies of Ni₃Al markedly in comparison with the Ni-23.75Al alloy. While addition of alloying elements, such as Ti, Mo, Ta, W and Re, occupying the Al sublattices dramatically increases the SISF and CSF energies of Ni₃Al. The results suggest that the energies of SISF and CSF are dependent both on the Al contents and on the site occupancy of the ternary alloying element in Ni₃Al intermetallic alloys.

A binary continuum model for dendritic solidification transport phenomena and corresponding numerical algorithm for the strong nonlinear coupling of T−f_S−C_L were extended to multicomponent alloys solidified under condition of Biot£0.1. Based on the extended model/algorithm, a method considering heat transfer was proposed to predict the solidification paths and microsegregation of alloys solidified under the same condition. The new algorithm and method were closely coupled with the commercial Thermo-Calc package via its TQ6-interface codes for instantaneous determination of the related thermodynamic data at each calculation time step. The sample simulation performed on an Al−2Si−3Mg alloy system indicates the availability and reliability of the model/algorithm and the proposed method for predicting solidification paths and microsegregation. Computional and experimental investigations on an Al−5.17Cu−2.63Si ternary alloy were conducted, and a reasonable agreement between the computation and experiment was obtained.

Thin-walled aluminum alloy tube numerical control (NC) bending with small bending radius is a complex process with multi-factor coupling effects and multi-die constraints. A significance-based optimization method of the parameters was proposed based on the finite element (FE) simulation, and the significance analysis of the processing parameters on the forming quality in terms of the maximum wall thinning ratio and the maximum cross section distortion degree was implemented using the fractional factorial design. The optimum value of the significant parameter, the clearance between the tube and the wiper die, was obtained, and the values of the other parameters, including the friction coefficients and the clearances between the tube and the dies, the mandrel extension length and the boost velocity were estimated. The results are applied to aluminum alloy tube NC bending d50 mm×      1 mm×75 mm and d70 mm×1.5 mm×105 mm (initial tube outside diameter D₀ × initial tube wall thickness t₀ × bending radius R), and qualified tubes are produced.

Numerical investigations on the flow field in Ti−Al melt during rectangular cold crucible directional solidification were carried out. Combined with the experimental results, 3-D finite element models for calculating flow field inside melting pool were established, the characteristics of the flow under different power parameters were further studied. Numerical calculation results show that there is a complex circular flow in the melt, a rapid horizontal flow exists on the solid/liquid interface and those flows confluence in the center of the melting pool. The flow velocity v increases with the increase of current intensity, but the flow patterns remain unchanged. When the current is 1000 A, the v_max reaches 4 mm/s and the flow on the interface achieves 3 mm/s. Flow patterns are quite different when the frequency changes from 10 kHz to 100 kHz, the mechanism of the frequency influence on the flow pattern is analyzed, and there is an optimum frequency for cold crucible directional solidification.

Electromagnetic forming (EMF) is a high-speed forming method which can be quite effective in increasing the forming limits of metal sheet. However, the EMF process is complicated due to magnetic-structure coupling analysis. Numerical simulation offers an opportunity to overcome the problem. Nevertheless, most present models for EMF process are limited to 2D axisymmetric model. So, a three-dimensional (3D) finite element model was established to analyze the electromagnetic sheet bulging. The contact between the sheet and the die and the effect of sheet deformation on the magnetic field analysis were both taken into consideration during the forming process. The simulation results of deflection at the sheet center and 20 mm away from the center were in agreement with the experimental ones. The plastic strain energy and plastic strain were analyzed.

The structural and electronic properties of TiC(110) surfaces are calculated using the first-principles total-energy plane-wave pseudopotential method based on density functional theory. The calculated results of structural relaxation and surface energy for TiC(110) slab indicate that slab with 7 layers shows bulk-like characteristic interiors, and the changes of slab occur on the outmost three layers, which shows that the relaxation only influences the top three layers. Meanwhile, the strong Ti—C covalent bonding can be found in the distribution of charge density on the (100) plane. The interlayer Ti—C chemical bonds are reinforced and the outermost interlayer distance is reduced as a result of the charge depletion in the vacuum and the charge accumulations in the interlayer region between the first and second layers. The surface energy of TiC(110) is calculated to be 3.53 J/m².

First-principle calculation was used to investigate the magnetic properties, electronic structure and bonding mechanism of FeF₂. By calculating the lattice parameters and magnetic moment as a function of effective interaction parameter (U_eff), it is found that the optimum value of U_eff is equal to 4 eV, the magnetic moment is 3.752 μB and the value of c/a is 0.704, which are in good agreement with the experiment results. Simultaneously, on the basis of GGA+U method, the electronic structure and bonding mechanism of FeF₂ were investigated by the analysis of electron localization function, Bader charge and total charge density. The results show that the bonding behavior between Fe and F atoms is a combination of ionic and covalent bond.

The influence of supercooled melt forced lamina flow on microsegregation was investigated. The concentration distribution at solid−liquid boundary of binary alloy Ni−Cu was simulated using phase field model coupled with flow field. The microsegregation, concentration maximum value, boundary thickness of concentration near upstream dendrite and normal to flow dendrite, and downstream dendrite were studied quantitatively in the case of forced lamia flow. The simulation results show that solute field and flow field interact complexly. Compared with melt without flow, in front of upstream dendrite tip, the concentration boundary thickness is the lowest and the concentration maximum value is the smallest for melt with flow. However, in front of downstream dendrite tip, the results are just the opposite. The zone of poor Cu in upstream dendrite where is the most severely microsegregation and shrinkage cavity is wider and the concentration is lower for melt with flow than that without flow.

Electron beam welding of Ti-15-3 alloy to 304 stainless steel (STS) using a copper filler metal was carried out. The temperature fields and stress distributions in the Ti/Fe and Ti/Cu/Fe joint during the welding process were numerically simulated and experimentally measured. The results show that the rotated parabola body heat source is fit for the simulation of the electron beam welding. The temperature distribution is asymmetric along the weld center and the temperature in the titanium alloy plate is higher than that in the 304 STS plate. The thermal stress also appears to be in asymmetric distribution. The residual tensile stress mainly exists in the weld at the 304 STS side. The copper filler metal decreases the peak temperature and temperature grade in the joint as well as the residual stress. The longitudinal and lateral residual tensile strengths reduce by 66 MPa and 31 MPa, respectively. From the temperature and residual stress, it is concluded that copper is a good filler metal candidate for the electron beam welding of Ti-15-3 titanium alloy to 304 stainless steel.

To improve the power efficiency and optimize the configuration of cold crucible using for continuous melting and directional solidification (DS), based on experimental verification, 3D finite element (FE) models with various configuration-elements were developed to investigate the magnetic field in cold crucible. Magnetic flux density (B) was measured and calculated under different configuration parameters. These parameters include the inner diameter (D₂), the slit width (d), the thickness of crucible wall, the section shape of the slit and the shield ring. The results show that the magnetic flux density in z direction (B_z) both at the slit and at the midpoint of segment will increase with the decrease of D₂ or with the increase of the width of the slit and the section area of wedge slit or removing the shield ring. In addition, there is a worst wall thickness that can induce the minimum B_z for a cold crucible with a certain outer diameter.

The squeeze cast process parameters of AZ80 magnesium alloy were optimized by morphological matrix. Experiments were conducted by varying squeeze pressure, die pre-heat temperature and pressure duration using L₉(3³) orthogonal array of Taguchi method. In Taguchi method, a 3-level orthogonal array was used to determine the signal/noise ratio. Analysis of variance was used to determine the most significant process parameters affecting the mechanical properties. Mechanical properties such as ultimate tensile strength, elongation and hardness of the components were ascertained using multi variable linear regression analysis. Optimal squeeze cast process parameters were obtained.

The Ce−La−O system was investigated via experiments and thermodynamic modeling. A series of CeO₂−LaO_1.5 mixtures were prepared by co-precipitation technique and examined by X-ray diffraction. Mutual solubilities between LaO_1.5 and CeO₂ at    1273 K were determined. Using the new experimental data together with literature information, a set of self-consistent thermodynamic parameters for the CeO₂−LaO_1.5 system were optimized. Combined with thermodynamic descriptions of Ce−O and La−O systems from literature, several property diagrams of Ce−La−O system were calculated and used to explain oxidation process of the Ce−La alloys. The fluorite phase is the unique oxidation products for most of the Ce−La alloys.

The electronic structures and mechanical properties of Al₄Sr, Mg₂Sr and Mg₂₃Sr₆ phases were determined by the use of first-principles calculations. The calculated heat of formation and cohesive energy indicate that Al₄Sr has the strongest alloying ability as well as the highest structural stability. The elastic parameters were calculated, and then the bulk modulus, shear modulus, elastic modulus and Poisson ratio were derived. The ductility and plasticity were discussed. The results show that Al₄Sr and Mg₂Sr phases both are ductile, on the contrary, Mg₂₃Sr₆ is brittle, and among the three phases, Mg₂Sr is a phase with the best plasticity.
附件:19-p2677-23027

The implementation of high pressure die casting (HPDC) filling process modeling based on smoothed particle hydrodynamics (SPH) was discussed. A new treatment of inlet boundary was established by discriminating fluid particles from inlet particles. The roles of artificial viscosity and moving least squares method in the present model were compared in the handling pressure oscillation. The final model was substantiated by simulating filling process in HPDC in both two and three dimensions. The simulated results from SPH and finite difference method (FDM) were compared with the experiments. The results show the former is in a better agreement with experiments. It demonstrates the efficiency and precision of this SPH model in describing flow pattern in filling process.

In order to study influences of geometric parameters on the T-shaped components local loading process, a new mathematical model considering the fillet radius and draft angle was established by using the slab method. The results obtained by the mathematical model agree with the data form experiment and numerical simulation, and the results are closer to the experimental and simulation results. The influence of draft angle may be neglected under the forming conditions used. The influence of fillet radius is notable, especially in the case that the ratio of fillet radius to rib width is less than 0.75.

The theoretical analysis of springback in rotary stretch bending process of L-section extrusion was studied. The models for characterizing the springback angle after unloading were established based on the stress and strain distributions in the cross-section of the part. With the proposed model, analysis of the effect of pre-stretch force and post-stretch force on springback angle shows that springback decreases as the pre-stretch force or post-stretch force increases. Comparative study with experiments clearly demonstrates that the prediction of springback can resort to the current model without the loss of accuracy.

In order to predict the buckling of stiffeners in the press bend forming of the integral panel, a method for solving the critical buckling load of the stiffeners in press bend forming process was proposed based on energy method, elastic-plastic mechanics and numerical analysis. Bend to buckle experiments were carried out on the designed press bend dies. It is found that the predicted results based on the proposed method agree well with the experimental results. With the proposed method, the buckling of the stiffeners in press bend forming of the aluminum alloy integral panels with high-stiffener can be predicted reasonably.

Based on the hexagonal crystallite model of graphite, the electrochemical characteristics of carbon atoms on the edge and basal plane were proposed by analyzing graphite crystal structure and bonds of carbon atoms in different sites. A spherical close-packed model for graphite particle was developed. The fractions of surface carbon atoms (SCA) and edge carbon atoms (ECA) were derived in the expression of crystallographic parameters and particle size, and the effects of ECA on the initial irreversible capacity and the mechanisms of action were analyzed and verified. The results show that the atoms on the edge are more active for electrochemical reactions, such as electrolyte decomposition and tendency to form stable bond with other atoms and groups. For the practical graphite particle, corresponding modifying factors were introduced to revise the difference in calculating results. The revised expression is suitable for the calculation of the fractions of SCA and ECA for carbon materials such as graphite, disordered carbon and modified graphite.

Ultrasound with different intensities was applied to treating AZ80 alloy melt to improve its solidification structure. The average grain size of the alloy could be decreased from 303 to 148 μm after the ultrasound with intensity of 30.48 W/cm² was applied. To gain insight into the mechanism of ultrasonic treatment which affected the microstructure of the alloy, numerical simulations were carried out and the effects of different ultrasonic pressures on the behaviors of cavitation bubble in the melt were studied. The ultrasonic field propagation in the melt was also characterized. The results show that samples from different positions are subjected to different acoustic pressures and the effect of grain refinement by ultrasonic treatment for these samples is different. With the increase of ultrasonic intensity, the acoustic pressure is increased and the grain size is decreased generally.

The distribution of magnetic forces and current on sheet and coil was analyzed in detail according to the structural parameter of the coil which was invalid. The result shows that the current direction based on simulation result agrees with the principles of uniform pressure electromagnetic actuator. The reason for coil failure was proposed. Then the magnetic forces on the sheet were input into an explicit finite element software ANSYS/LS-DYNA to analyze the deformation law of the sheet.

First-principles calculations were carried out to investigate the structural stabilities and electronic properties of RhZr. The plane wave based pseudopotential method was used, in which both the local density approximation (LDA) and the generalized gradient approximation (GGA) implanted in the CASTEP code were employed. The internal positions of atoms in the unit cell were optimized and the ground state properties such as lattice parameter, density of state, cohesive energies and enthalpies of formation of ortho-RhZr and cubic-RhZr were calculated. The calculation results indicate that ortho-RhZr can form more easily than cubic-RhZr and the ortho-RhZr is more stable than cubic-RhZr. The density of states (DOS) reveals that the strong bonding in the Rh−Zr and Rh−Rh or Zr−Zr interaction chains accounts for the structural stability of ortho-RhZr and the hybridization between Rh-4d states and Zr-4d states is strong.

The Co−Cr−W ternary system was critically assessed using the CALPHAD technique. The solution phases including the liquid, g-Co, e-Co and a-Cr were described by a substitutional solution model. The σ, μ and R phases were described by three-sublattice models of (Co,W)₈(Cr,W)₄(Co,Cr,W)₁₈, (Co,Cr,W)₇W₂(Co,Cr,W)₄ and (Co,W)₂₇(Cr,W)₁₄(Co,Cr,W)₁₂, respectively, in order to reproduce their homogeneity ranges. A self-consistent set of thermodynamic parameters for each phase was derived. The calculated isothermal sections at 1 000, 1 200 and 1 350 °C are in good agreement with the experimental data. A eutectoid reaction of R m+g-Co+s in this ternary system was predicted to occur at 1 022 °C.

The analytical model for springback in arc bending of sheet metal can serve as an excellent design support. The amount of springback is considerably influenced by the geometrical and the material parameters associated with the sheet metal. In addition, the applied load during the bending also has a significant influence. Although a number of numerical techniques have been used for this purpose, only few analytical models that can provide insight into the phenomenon are available. A phenomenological model for predicting the springback in arc bending was proposed based on strain as well as deformation energy based approaches. The results of the analytical model were compared with the published experimental as well as FE results of the authors, and the agreement was found to be satisfactory.

The inhomogeneity of density and mechanical properties of A357 aluminum alloy in the semi-solid state were investigated. Numerical simulation and backward extrusion were adopted to study the preparation of cup shells. The results show that the relative density of the wall is the lowest in samples, and that of the base is the highest. With increasing the billet height, more time is needed for relative density of the corner to reach the maximum value, and the relative densities in every region improve evidently with increasing the pressure. The tensile stress was simulated to be the largest at the corner, and the hot tearings were forecasted to mainly appear at the corner too. By employing proper billet height and pressure, the extruded samples consisted of fine and uniform microstructures, and can obtain excellent mechanical properties and Brinell hardness.