According to modified Miedema’s theory, mixing enthalpies (ΔH), excess entropies (SE), excess Gibbs free energy (GE), and component activities (a) of Cu–La binary alloy were estimated using the basic thermodynamic principles and some simple physical parameters of Cu and La, such as electronegativity, atomic volume and electron density. Based on the Cu–La binary alloy phase diagram, the Gibbs free energy of the phase precipitation reactions of Cu6La and Cu5La was deduced. The results showed that the values of ΔH, SE, and GE of Cu–La binary alloy were all negative. Compared to the ideal solution, the activities of the components presented a large negative deviation from Raoult’s law, which indicated that there was a strong interaction between Cu and La. The calculated data are well consistent with the experimental data. The Gibbs free energies of the phase precipitation reactions of Cu6La are lower than those for Cu5La, which means that Cu6La is thermodynamically more stable than Cu5La. Furthermore, the experimental results show that rareearth rich Cu6La phase particles in copper matrix are formed after La microalloying.

Twinning and detwinning are the important deformation modes in magnesium alloys during cyclic loading at room temperature. To analyze these two deformation mechanism, cyclic compression–tension experiments were performed on Mg–3Al–1Zn rolled sheet along the rolling direction. In these tests, the microstructure evolutions of a series of grains during deformation were traced by using quasi in situ electron backscatter diffraction (EBSD). Important quantities like the Schmid factors of twinning system, the fraction of twinning during compression, and the fraction of twinning after reverse loading were calculated on the basis of measured quantities. The influence of Schmid factor of twinning variants on detwinning upon reverse loading was analyzed. Detwinning would prefer to proceed during reverse loading if the Schmid factor of twinning in the twinning area before reverse loading is sufficiently large.

Deformation and texture evolution of AZ31B magnesium (Mg) alloy sheet under uniaxial tension, compression, and reverse loading after different pre-strain (compression and tension) were investigated experimentally. The results indicate that the pre-compressive strain remarkably affects the reverse tensile yield stress and the width of the detwinning-dominant stage during inverse tension process. Similar to stress–strain curve of the uniaxial compression, the curve of reverse tensile yield value also has ‘S’ shape, and its minimum value is only 38 MPa. The relationship between pre-compressive strain and the width of detwinning-dominant stage presents a linear growth, and the greater the pre-compressive strain is, the smaller the strain hardening rate of the detwinning-slip-dominant stage is. Compared with the reverse tension under pre-compression, the influence of the pre-tension deformation on the deformation mechanism of subsequent compression is relatively simple. With the increase in pre-tension strain, the yield stress of the reverse loading is rising.

Developments of new sheet metal forming technology and theory in China are reviewed in detail in this paper. Advances of crystal plasticity on the deformation mechanism of Mg alloy are firstly described, especially its applications on the prediction of sheet forming process. Then, a new macroscopic constitutive model is introduced, which possesses an enhanced description capacity of tension/compression anisotropy and anisotropic hardening. In order to take into account the twinning process of hexagonal close-packed material, a modified hierarchical multi-scale model is also established with adequate accuracy in a shorter computational time. The advanced forming limit of sheet metal, mainly about aluminum alloy, is also investigated. Besides the above theory developments, some new sheet metal forming technologies are reviewed simultaneously. The warm forming technology of Mg alloy is discussed. New processes to form sheet parts and to bend tubes are proposed by using hard granules. On the other hand, a new kind of ultra-high-strength steel based on typical 22MnB5 by introducing more residual austenite and Cu-rich phase to increase the elongation and strength and its novel forming method that integrates hot stamping and quenching participation are proposed. Progresses in sheet hydroforming, press forging and electromagnetic forming of sheet metal parts are also summarized.

The effects of small amount addition of the rare-earth Ce on the microstructure, mechanical properties, and corrosion resistance behavior of cast pure copper were investigated using optical microscopy, scanning electron microscopy, energy-dispersive x-ray spectrometry (EDS), transmission electron microscopy (TEM), tensile testing, and potentiodynamic polarization measurements. It was indicated that Ce addition significantly refined the grain and enhanced the tensile strength of cast pure copper. Copper alloy with 0.12 wt.% Ce addition had the smallest equiaxed grains of 358. ± 23.53 μm and the ultimate tensile strength of 181.7 ± 3.7 MPa. Ce formed spherical second phase particles with copper, which were revealed as Cu6Ce by EDS and TEM results. Solid solution strengthening, fine-grain strengthening, and second-phase precipitation strengthening played important roles in the tensile strength improvement. However, the elongation decreased due to the second phase particles’ inhomogeneous distribution. The corrosion resistance properties of micro-alloyed copper alloys in 0.5 mol/L HCl solution were improved when Ce addition was limited to less than 0.069 wt.% owing to a purification effect and the formation of a compact corrosion product film on the copper matrix. The influencing mechanisms of Ce on the microstructure, mechanical property, and corrosion property were also discussed in detail.

•In-situ tracking on the evolution of grains orientation of magnesium alloy was carried out by EBSD.•Distributions of twin bands were closely related to the activation of extension twin variants.•Activation of extension twin significantly changes the order of Schmid factor of slips.•Pyramidal slips become the dominant deformation mode at the late stage of compression.In-situ tracking on the evolution of grains orientation of rolled magnesium alloy sheets compressed uniaxially at room temperature was carried out by the method of electron backscatter diffraction (EBSD), and meanwhile, distributions of twin bands, activations of twin and slips were also analyzed. The results show that the distributions of twin bands were closely related to the activation of extension twin variants. The activation of extension twin significantly changes the order of Schmid factor of different slips, and accordingly affects the activation of slips during the subsequent deformation.

As-cast Cu-La alloys with La contents in the range of 0–0.32 wt.% were fabricated by vacuum melting method. The effects of La on microstructure and mechanical properties of as-cast pure copper were investigated using optical microscopy (OM), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and tensile test. The results showed that La had obvious effects on the solidification microstructure and the grain refinement of as-cast pure copper. With the increase of La content, the ultimate tensile strength, the yield strength and the microhardness increased gradually, but the elongation increased first and then decreased while La content exceeded 0.089 wt.%. The improvement of mechanical properties was attributed to the effect of grain refinement strengthening, solid solution strengthening, second phase strengthening and purifying. However, excessive adding La would deteriorate the elongation owing to the excessive Cu6La phases.The addition of trace La can lead to the formation of the columnar grain, while the addition of much La can provoke a transition from columnar grain structure to equiaxed grain structure

•A hierarchical multi-scale model is proposed to account for texture evolution.•It is achieved by the coupling of a phenomenal model and a polycrystal model.•The texture evaluation is performed at discrete steps when a criterion is met.•The model is supposed to be efficient for real-life process simulation.•The predicted results by the developed model agree well with the experiments.Due to the absence of sufficient number of slip systems in hexagonal close packed (hcp) metals to accommodate arbitrary plastic deformation, mechanical twinning occupies an important role in the mechanical behavior of these metals. Twinning causes a significant and abrupt change in the orientation of crystals, whilst simultaneously affecting the hardening and plastic flow behavior of the material considerably. Modeling of forming processes of hexagonal close packed metals thus requires accounting for the evolution of texture and texture induced anisotropy, especially due to twinning. Additionally, the computational framework for the simulation of forming processes must be reliable and efficient in order to guarantee results in realistic time frames. In the present work, a phenomenological constitutive model consisting of an anisotropic yield function, associate flow rule and isotropic hardening, is coupled with the viscoplastic self-consistent polycrystal model in order to capture the slip and twinning activity, texture evolution and the evolving anisotropy during plastic deformation of hcp materials, similar to a hierarchical multi-scale modeling framework proposed by Van Houtte et al. [41] for cubic metals. To account for texture evolution during plastic deformation, the parameters involved in the anisotropic yield function are regularly updated based on mechanical test data obtained from the polycrystal model at the micro-scale. The parameter update is performed at discrete steps instead of every increment. The developed model is applied to describe the behaviors of pure zirconium at liquid nitrogen temperature. The results of the numerical simulations were found to be good agreement with experimental results, and at acceptable computation time.

In order to investigate the micro-mechanism of warm forming of Mg alloys, three specimens cut from a rolled AZ31 sheet were chosen to be compressed along the Rolling Direction (RD) at 100 °C, 170 °C and 230 °C, separately. During compression, an in situ measurement of grain orientation in the plane of RD × TD (Transverse Direction) was carried out with EBSD method. Experimental and analytical results show that temperature has remarkable impact on activation of twinning and variation of texture. As the temperature was raised from 100 °C to 230 °C, the number of grains with twins activated decreased substantially during deformation, and rolling texture varied from quick vanishing at 100 °C to always existing at 230 °C. Tracing for orientation of individual grains during deformation shows that there are obvious different orientation changes between grains with twins activated and those without twins activated. Twinning plays a significant effect on texture variation during compression. The extension twin variant really activated during deformation is the one with maximal Schmid factor.Highlights► An in situ tracing of grain orientations during compression was carried out. ► Changes of basal texture of rolled sheets during compression at different temperatures were compared. ► The extension twin variants were decided by some ways. ► The relationship of extension twin variant activation and Schmid factor was obtained.

The effect of loading modes of tensile deformation on the mechanical properties of a metastable austenite stainless steel has been investigated. The stress–strain curves, microstructures and fraction of the martensite are measured and analyzed separately. The results of tensile test indicate that a special loading mode referred as cyclic tensile loading and unloading can improve the strength and the formability of the specimens effectively. It is noted that the elongation and the ultimate strength are increased by 24.3% and 9.2% respectively at room temperature. Such enhancement of the transformation induced plasticity effect is mainly related to remarkable increase of the fraction of strain-induced martensite by the cyclic tensile loading and unloading.

The effects of feeding ratio on flange bending of shear spinning are investigated with analytical method. Firstly, influence of feeding ratio on total energy is analyzed utilizing the formula of shear spinning force and power derived by energy method. Subsequently, the connection between the deviation ratio and the thinning ratio, and the influence of feeding ratio on the thinning ratio are researched. Finally, the conclusions about the deviation ratio and flange bending are adopted to reveal the influential tendency of feeding ratio on flange bending. The results show that the flange bending towards headstock weakens with the increase of feeding ratio, which is verified by the experimental results very well. It indicates that the calculation method in this paper is reasonable.

The hot working characteristics of δ phase in the delta-processed Inconel 718 alloy during isothermal compression deformation at temperature of 950 °C and strain rate of 0.005 s− 1, were studied by using optical microscope, scanning electron microscope and quantitative X-ray diffraction technique. The results showed that the dissolution of plate-like δ phase and the precipitation of spherical δ phase particles coexisted during the deformation, and the content of δ phase decreased from 7.05 wt.% to 5.14 wt.%. As a result of deformation breakage and dissolution breakage, the plate-like δ phase was spheroidized and transferred to spherical δ phase particles. In the center with largest strain, the plate-like δ phase disappeared and spherical δ phase appeared in the interior of grains and grain boundaries.

Although the rigid plastic finite element method (RPFEM) is extremely efficient and particularly suitable for analyzing the strip rolling, it is unavailable for online application due to the large computational time. During iterative solution of RPFEM, the convergence speed is greatly determined by the initial guess. In this paper, three different initial guesses are constructed through Engineering Method, G Functional and Neural Network, respectively. Especially, the back propagation neural network model for predicting the relative velocity field (nodal velocities/roll speed) is trained from huge amounts of RPFEM results. Whereafter, the initial guess is calculated by multiplying the predicted relative velocity field by the roll speed. The numerical examples of seven passes hot strip rolling are provided to show the solution efficiency and the accuracy of RPFEM code in the cases of different initial guess. Compared with other two methods, the Neural Network has the remarkable advantages to reduce the CPU time and the iterations of RPFEM code. From the numerical results, it is found that the CPU time, stability and the accuracy of RPFEM code in the initial guess by the Neural Network can meet the requirements of online control completely in hot strip rolling.

The calculation method and three-dimensional thermo-mechanical coupling model were established for the planetary rolling process of TP2 copper tubes. The distribution rules of temperature field of TP2 copper tubes were obtained by simulation analysis. The temperature of the TP2 copper tubes increases from room temperature to about 700 °C in three-roll planetary rolling, which would reduce the rolling force, and improve the performance of the rolled copper tubes. The temperature of TP2 copper tubes during rolling was in good agreement with the measured results, which indicates that the finite-element method would supply important reference merit for 3-D thermo-mechanical simulation of TP2 copper tubes in the three-roll planetary rolling process.

During three-roll planetary rolling, the microstructure of copper tube with initial columnar grains develops into an equiaxed grain structure due to the large rolling deformation and high rolling temperature. The microstructure of copper tubes significantly influences formability and properties due to the three-roll planetary rolling operation. It is very important to understand the microstructural evolution for such special processing. It was found that dynamic recrystallization occurred at the concentrating deformation zone, followed by rapid grain expansion that gradually stabilized. Corresponding with the transformation of microstructure, the hardness of the tube billet reduced gradually away from the roller’s concentrating deformation zone. The changing of roller velocity is responsible for the extreme evolution of the microstructure in the concentrating deformation zone. Therefore, the properties of copper tubes can be controlled by concentrating the deformation zone. This research can facilitate the application of planetary rolling to the manufacture of tubes for low formability materials.

The present work has been focused on the warm deep drawing process by superimposing a thermal gradient between the blank centre in contact with the punch and the blank flange (which is going to be drawn). Using such a technique the limit drawing ratio of Mg alloys can be dramatically improved. As a case of study, the forming of cylindrical AZ31 cups was investigated. In particular, the attention was focused on the forming temperature (in both the flange region and in the blank centre). Finite element simulations were run in order to investigate the stress and strain distribution in the material determined by the temperature gradient and to validate experimental results. Tests highlighted that a LDR equal to 3.375 is possible when setting the temperature of the blank holder at 230 °C and the punch speed at 6 mm/min.

Ball spinning, a special process to manufacture wall-thinned tubes with small diameter, has been used widely in recent years, although it was invented decades years ago. Many researchers are trying to develop various equipment to meet their requirements, such as to produce conical wall tubes, stepped wall tubes, etc., but the machine introduced in this article is very different from the setups mentioned above. The rolling balls in this machine can be forced to move in the radical directions to shape tubes according to CNC programs. In this paper, the working system, the special working female die and other characteristics of the CNC ball-spinning machine are introduced in detail.

The state-of-the-art of metal forming technology is summarized. It is suggested that metal forming technology be based on mechanics of solids and materials physics to become a full science. Materials science of macro- and micro-structure should be considered jointly. The theory of metal forming can then be fully developed and a tremendous breakthrough made. Computational mechanics and software technology are used to visualize virtual metal forming processes. Metal forming processes and equipment are computer-controlled by using computer technology and automatic control theories. New metal forming technologies may be developed using new energy resources, new forming mediums and new loading methods. New metal forming technologies are required to be developed for new materials and new products according to the needs of the automotive, electrical, electronic and aerospace industries.

In this paper, recent developments in sheet hydroforming technology are summarized, several key technical problems to be solved for the development of sheet hydroforming technology are analyzed, and varied sheet hydroforming technologies are discussed. Compound deformation by drawing and bulging is the main direction for the development of sheet hydroforming technology, in which it is advantageous to increase the feeding of materials, and the ratio of drawing deformation (drawing in of the blank flange) to bulging, enabling the forming limit of a sheet blank to be increased. It is also advantageous to increase the local deformation capacity for sheet hydroforming, to increase the range of application of the process. Press capacity is one of the important factors restraining the range of applications. As one of the flexible forming technologies that is still under development, it has much potential for innovative applications. Its applications have been increasing remarkably, recently in automotive companies. A breakthrough in the technology will be obtained by the development of novel equipment. A new sheet hydroforming technology using a movable die is proposed in this paper, which has been developed recently by the authors.

The hydromechanical deep drawing processes of mild steel cups have been investigated experimentally and numerically. Experiments were carried out with the fixed gap method (with spacers) and the conventional method (without spacers) under different prebulging pressures. The shape variations and the thickness distributions of the workpieces were measured and discussed. The effects of anisotropy and prebulging pressure on the final product quality are discussed. The processes were analyzed by the explicit finite element code DYNA3D with the Barlat–Lian’s three-parameter material model. The numerical results are compared with those obtained in the experiments.

The hydromechanical deep drawing process of aluminum cups and mild steel cups is analyzed experimentally and numerically. The effects of the process parameters on the final product quality are discussed. A working zone with a suitable maximum chamber pressure is obtained from the experimental results. The explicit finite element method is used with Hill’s transversely anisotropic material model for the numerical analysis. The numerical results are compared with those obtained in the experiments, process defects of local thinning are predicted and the thickness variations are discussed.

Tapered rectangular boxes of aluminum and mild steel were formed using the hydromechanical deep drawing process. The experiments are described and discussed, and the process is analyzed numerically using the explicit finite element method. The numerical results are discussed and compared with the experimental results. Blanks of octagonal shape and circular shape and of various dimensions are simulated and compared, suggestions being made on this basis. The failure modes of local thinning and body wrinkling occurring in the experiments are predicted.

The flow behavior and dynamic globularization of TC11 titanium alloy during subtransus deformation are investigated through hot compression tests. A constitutive model is established based on physical-based hardening model and phenomenological softening model. And based on the recrystallization mechanisms of globularization, the Avrami type kinetics model is established for prediction of globularization fraction and globularized grain size under large strain subtransus deformation of TC11 alloy. As the preliminary application of the previous results, the cogging process of large size TC11 alloy billet is simulated. Based on subroutine development of the DEFORM software, the coupled simulation of one fire cogging process is developed. It shows that the predicted results are in good agreement with the experimental results in forging load and microstructure characteristic, which validates the reliability of the developed FEM subroutine models.

In this paper, a fast rigid plastic finite element method (FEM) is developed for online application in strip rolling. Firstly, a refined neural network model is established to generate an initial guess for the start of the Newton-Raphson iteration. Secondly, the Hessian matrix is divided into sub-domains for parallel computing. Thirdly, the Brent’s method is adopted to speed up the line search for the relaxation factor. Fourthly, the energy functional is partitioned according to the numbering of elements for parallel computing. Fifthly, an energy method with high numerical stability is proposed for predicting the rolling force. Finally, the numerical examples for the strip rolling show that the fast rigid-plastic FEM can meet the requirements both on the computational time and the accuracy.

The pure copper ingots with different microalloying lanthanum (La) addition were cold rolled to a cumulative area reduction of 80% at room temperature and then subjected to various annealing treatments. The results show that the recrystallization of alloys was retarded at first and then promoted with increasing La concentration. It is noted that the recrystallization of alloys with a small amount of La was retarded. But, the recrystallization of alloys with a large amount of La was accelerated. In addition, the models of recrytallization kinetics of alloys were established to predict the recrystallisation degree of the deformed pure copper with different lanthanum addition during an isothermal annealing.

The orientation evolution of Mg alloy grains was in-situ tracked during compression at 100 °C by the method of electron backscatter diffraction, and meanwhile, quantitative analysis was also conducted on activations of slips and twinning. Effects of extension twinning activation on slips activations were analyzed during deformation based on calculation of variations of Schmid factor for different slips before and after twinning. It is predicted that there are not distinct changes for Schmid factor of basal slips before and after twinning for Mg alloy grains with basal textured orientation, while the Schmid factor of prismatic slips decreases distinctly after twinning and accordingly they are hard to be activated during the subsequent deformation. Simultaneously, the Schmid factor of pyramidal slips increases distinctly after twinning and it is relatively easy for them to be activated during the subsequent deformation.