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In this study, extrusion experiments were carried out on Al-Mg-Si-Cu-Mn alloys with different extrusion ratios (ERs), extrusion temperatures (ETs), and extrusion speeds (ESs). By using electron backscatter diffraction (EBSD) analysis, tensile testing, and other analytical means, the evolution of microstructure, texture, and properties of the extruded alloys was systematically investigated, and the strengthening-toughening mechanism induced by the extrusion parameters was revealed. It was found that the strength of the extruded alloy shows a tendency to first increase and then decrease with the increase of the ER and ES, and the 'critical ER' and 'critical ES' are 29.5 and 2.5 mm/s, respectively; the strength of the extruded alloy gradually increases with the increase of the ET. The alloy achieved excellent strength-toughness matching at the ER of 29.5, ET of 480 °C, and ES of 2.5 mm/s. The yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) of the extruded alloy at this condition were ∼169.58 MPa, ∼314.36 MPa, and ∼16.57 %, respectively. This excellent strength-toughness matching is mainly related to the following aspects: 1) grain refinement provides high grain boundary strengthening effect and appropriate work hardening ability; 2) <111>//ED texture has a strong preferential orientation; 3) the variation trend of dislocation density is importantly related to <111>//ED and EX a {011}<111> textures; 4) Cube{001}<100> and Goss{011}<100> textures have a softening effect. The above findings provide new insights into the potential mechanisms of hot extrusion forming of aluminum alloys, which are of important guiding for the design and development of aluminum alloys with excellent strength-toughness combinations. [Display omitted] • <100>//ED texture is related to Cube{001}<100> and Goss{011}<100> textures. • Cube{001}<100> and Goss{011}<100> textures have a softening effect. • <111>//ED texture has a strong preferential orientation. • Dislocation density is importantly linked to <111>//ED and EX a {011}<111> textures. • Excellent strength-toughness matching of Al-Mg-Si-Cu-Mn extrusion alloys can be realized under specific extrusion parameters. [ABSTRACT FROM AUTHOR]

The solution and aging experiments on cold-rolled 2024 Al alloy sheet were carried out. The parameters of solution temperature, solution time, aging temperature, and aging time were combined by orthogonal design, and their effects on the microstructure and overall performances of the 2024 Al sheet were studied. The results showed that aging temperature exhibited the most significant effect, followed by solution time and solution temperature, while the effect of aging time was slight. An integrated balance method was employed to optimize the solution and aging parameters, and the optimum heat treatment condition was determined as solution at 500 °C×70 min followed by artificial aging at 180 °C ×16 h. Compared with the orthogonal experimental results, it was found that the optimized solution parameters could lead to a higher dissolution degree of S (Al2CuMg) and θ (Al2Cu) phases on the premise of preventing excessive grain growth and over-burning. The optimized aging parameters could not only promote the precipitation of fine GPB zone and S phase, but also avoid the coarsening of S phase and narrow the precipitation free zone (PFZ) at grain boundary. By optimization, the ultimate tensile strength (UTS), yield strength (YS), elongation, hardness, and conductivity of 2024 Al sheet reached the excellent values of 527 MPa, 411 MPa, 12.5%, 148.9 HV, and 37.4% IACS, respectively. [ABSTRACT FROM AUTHOR]

During the cold and hot deformation of metals, the nonlinearity in unloading is mainly caused by dislocation-associated behaviors and creates challenges for the prediction of springback law and residual stress distribution after springback. In this paper, a unified physically-based model for describing the dislocation density evolution in unloading after cold and hot deformation was proposed firstly by considering the combined effects of reverse slip of reversible mobile dislocations (under back stress and the static recovery) and recrystallization (after deformation) on the dislocation density evolution in unloading. Furthermore, an anelastic strain model associated with dislocation behaviors was established for predicting the microplastic strain in unloading after cold and hot deformation by considering the effects of strain-induced dislocation multiplication and the dislocation annihilation/consumption caused by dynamic recovery and dynamic recrystallization on the reversible mobile dislocation density evolution during deformation. The established dislocation density evolution model and anelastic strain model were evaluated using the experimental results obtained from the hot compression of homogenous aluminum alloys and the cold compression of extruded aluminum alloys. The results indicated that the established models are able to accurately predict nonlinear unloading behavior and nonlinearly varying microplastic strain. Meanwhile, it was also found that, for cold deformation, the reverse slip of reversible mobile dislocations driven by back stress is the leading reason for the nonlinearity of unloading, and the strain hardening and recovery during deformation are main factors affecting the anelasticity of unloading; for hot deformation, the reverse dislocation slip, static recovery and recrystallization collectively affect the nonlinearity in unloading, and the anelasticity is affected not only by strain hardening and dynamic recovery but also by dynamic recrystallization during loading process. [Display omitted] • The cold and hot deformation-unloading mechanism and springback nature of aluminum alloys were studied. • A new unified physically-based model for describing the dislocation density evolution in unloading was proposed. • An anelastic strain model associated with dislocation behaviors for predicting microplastic strain was established. • The established models can accurately predict nonlinear unloading behavior and nonlinearly changing microplastic strain. [ABSTRACT FROM AUTHOR]

For improving production efficiency and saving energy, various manufacturing technologies for integrating solid-state joining and plastic forming processes have become hot topics in recent years. Hot deformation and solid-state bonding of materials are essences for the integration of solid-state joining and plastic forming processes. This study compared the hot deformation and solid-state bonding behavior of an Al-Mg-Si alloy at the temperatures ranging from 673 to 803 K and the strain rates ranging from 0.001 to 10 s−1 using conventional hot isothermal compression tests (CHICT) and hot isothermal compression bonding tests (HICBT). The flow stress behavior of the material during CHICT and HICBT was compared, and a constitutive equation was established based on the true stress-strain curves obtained from HICBT. The evolution of grain structure and bonding interface in the processes of hot deformation and solid-state bonding was investigated. Furthermore, the quantitative relationship between the interfacial bonding degree and the temperature and strain rate was established, and the relationship between the bonding degree and the mechanical properties of the welds was discussed. A new parameter, RSS, was proposed to evaluate the solid-state weldability of materials. [ABSTRACT FROM AUTHOR]

Abstract Aluminum alloy profiles manufactured by semi-continuous porthole die extrusion have three kinds of intrinsic features: longitudinal welds, transverse welds and back-end defects, which affect the corrosion resistance and mechanical properties of the profiles. In this work, the microstructure, corrosion resistance and mechanical properties of these intrinsic features were studied by microstructural characterization, chemical immersion and in-situ test, and the relationship between the material flow behavior and the evolution of the back-end defect and transverse weld was revealed through numerical simulation. It is found that, in terms of corrosion resistance and mechanical properties, both the transverse weld and back-end defect are poor, while the longitudinal weld is relatively good. Impurities and oxide particles are densely distributed in the aluminum alloy matrix in the back-end defect area. In the transverse weld area, the bonding interface has impurities and oxides, and grains are separated by the bonding interface; while in the longitudinal weld area, the grains across the bonding interfaces are formed. The bonding interface of the ring-shaped transverse weld which is far from the longitudinal weld has a low bonding degree. When the transverse weld becomes no longer ring-shaped and very close to the longitudinal weld, its bonding degree is greatly enhanced. The bonding degree of all the transverse welds is lower than that of all the longitudinal welds. During the tensile tests of the extruded profiles, strain concentration phenomena occur at the positions of the longitudinal welds, transverse welds and back-end defects, and there are two types of fracture modes: "uniform plastic deformation → strain concentration → fracture" and "uniform plastic deformation → strain concentration → debonding → fracture". [ABSTRACT FROM AUTHOR]

The unloading process of hot-deformed aluminum alloys exhibits obvious strain rate- and deformation temperature-dependent nonlinearity and the springback is generated by internal stress relaxation, which affects the forming accuracy of aluminum alloy components. The strain hardening and dynamic softening during deformation as well as static softening during unloading affect the springback of hot-deformed aluminum alloys. In this study, the homogeneous aluminum alloys samples were used to perform the single-pass isothermal hot compression and unloading tests with different deformation temperatures, loading strain rates and strains. The strain-, strain rate- and deformation temperature-dependent unloading and springback behavior of hot-deformed aluminum alloys were studied. The effects of strain hardening, dynamic and static softening on the springback behavior of alloys were revealed. The relationships between unloading stress, springback strain and instantaneous tangent modulus in unloading were analyzed. A polynomial-type equation was proposed according to the nonlinear unloading stress-strain curves. The microscopic mechanism of nonlinear unloading of hot-deformed aluminum alloys was also clarified based on the physical mechanism of internal stress relaxation and anelastic strain accumulation. A micro-mechanism-based model was developed to describe the springback and internal stress relaxation in unloading after hot deformation of aluminum alloys. The comparison of calculated unloading curves with experimental results indicates that the proposed polynomial-type equation and developed micro-mechanism-based model can describe accurately the nonlinear springback and stress decay in unloading of hot-deformed aluminum alloys, which provide a prerequisite for analyzing the final geometry and residual stress of precision hot-deformed alloy components. [Display omitted] • Strain-, strain rate- and temperature-dependent unloading behavior of hot-deformed aluminum alloys were studied firstly. • Springback strains in unloading, at saturated and zero-load state after hot deformation were analyzed. • A polynomial-type equation for nonlinear unloading stress-strain relationship was proposed. • A micro-mechanism-based model was established to predict springback and internal stress relaxation of hot-deformed parts. [ABSTRACT FROM AUTHOR]

Fine nanostructures of bonding interfaces of weld seams formed by porthole die extrusion in the absence/presence of a gas-pocket behind the bridge of the extrusion die were systematically studied to understand the underlying interfacial bonding mechanisms. Interfacial grain boundaries, nanoscale amorphous layers, and three kinds of new interfacial structures were found. Specifically, it was found that, in the absence of a gas-pocket behind the bridge, there are two distinctly different interfacial structures. For the first kind of bonding interface, interfacial grain boundaries exist in contact areas and micro-voids exist in non-contact areas. For the second kind of bonding interface, there are no interfacial grain boundaries in contact areas and only nanoscale micro-voids exist in non-contact areas. In the presence of a gas-pocket behind the bridge, nanoscale voids and amorphous layers exist at the bonding interface. It was also found that the formation of gas-pockets can be avoided by increasing the depth of the welding chamber, and the increase of the welding chamber's depth and extrusion speed also contributes to the volume reduction of micro-voids and the migration of grain boundaries at the bonding interface, so as to improve the welding quality of weld seams. Based on the experimental findings, two interfacial bonding mechanisms corresponding to the absence/presence of a gas-pocket are proposed. The specific behavior of micro-asperities contact, micro-voids closure, oxide films breaking and interfacial grain boundaries migration are described, and the solid-state bonding process during porthole die extrusion is revealed from the micro-nano scales. [ABSTRACT FROM AUTHOR]

Unloading-reloading behavior is of crucial importance in multi-pass forming of metal materials, the nonlinear of which creates challenges for the analysis of springback and residual stress of the precision manufacture components. Especially for the hot bulk-formed material at elevated temperature, the thermal-mechanical coupling effect makes the unloading-reloading process more complicated and thus more difficult to model and control, which remains to be solved. In this paper, the unloading-reloading behavior dependent on strain rate and deformation temperature and its model of hot compressive deformed aluminum alloys at elevated temperature were studied from the macroscopic and microscopic perspectives. The effect of deformation temperature, strain rate and strain on the unloading-reloading behavior of hot compressive deformed aluminum alloys were revealed, and corresponding micro-mechanism was elucidated and then discussed. Macroscopically, a strain-, strain rate- and temperature-dependent nonlinear macroscopic model describing unloading–reloading process was established, which can be used to describe the unloading stress relaxation and predict springback during multi-pass hot bulk forming. Microscopically, it is suggested that the relaxations of back stress and forest dislocation hardening stress collectively affect the unloading stress relaxation, due to the decrease of mobile and immobile (forest) dislocation density in unloading, while the dislocation-related behavior before yield, i.e. the dislocations' bowing-out under pinning, affects the reloading behavior. Based on the micro-mechanism, a physically-based micro-model for describing unloading–reloading was constructed which further is used to clarify the physical mechanism of internal stress relaxation and inelastic strain recovery under multi-pass hot compression deformation. The comparison of the calculation results of the models with those of experiments indicated that the established unloading–reloading macroscopic and microscopic models are able to predict the stress–strain response upon the unloading–reloading loop of multi-pass cyclic hot compression deformation. [Display omitted] [ABSTRACT FROM AUTHOR]

During continuous production of aluminum alloy profiles, the adjacent billet interface flows through die cavity and forms transverse weld in a certain length of the profile due to the unbalance flow of material. Bad transverse welding quality is one of most common effects during hollow profile extrusion. The purpose of this work is to investigate experimentally and numerically the extrusion transverse weld for a 7N01 aluminum alloy hollow profile. Numerically, the transient extrusion process were simulated based on HyperXtrude. By analyzing material flow behavior during extrusion process, the formation mechanism of the transverse weld was investigated and the influences of process parameters on transverse weld was studied. Experimentally, the porthole extrusion die was manufactured and the extrusion process was carried out, respectively. By numerical and experimental comparison and analysis, the numerical results was well verified, and the appropriate process parameters was determined to obtain good welding quality for this profile studied in this work. [ABSTRACT FROM AUTHOR]

As a typical plastic deformation process with high productivity, porthole die extrusion process has been widely used to produce a variety of aluminium alloy profiles. For the profiles extruded with porthole dies, the welding quality of longitudinal weld seams is the key factor to determine their performance. In this study, different types of welding defects from millimetre scale to nanometre scale were found during porthole die extrusion by varying extrusion die structure and process parameters. Furthermore, the formation mechanisms of these welding defects were studied from both the macro and micro levels. Finally, the factors influencing the welding quality of extruded profiles were summarized. It was found that the welding quality is determined by metal flow behaviour, solid state bonding process and microstructural evolution. The formation of the un-bonded macro-defects in the extruded profile is attributed to improper metal flow behaviour, while the formation of the micro-voids on the bonding interface is caused by the insufficient solid state bonding. In addition, the metal in the welding zone usually has the particular microstructure different from the other zones, since it experiences the special thermal and mechanical history. [ABSTRACT FROM AUTHOR]

Porthole die extrusion process of aluminum alloy profiles is a hot deformation process involving solid state welding. Microstructural evolution of welding seams is the key factor to determine mechanical properties of extruded profiles. In this work, the grain structure, bonding interface structure and precipitates of welding seams in the profiles extruded under different billet heating temperatures and extrusion speeds were characterized, and the hardness, strength and ductility of welding seams were analyzed. The influence of billet heating temperature and extrusion speed on the microstructure and mechanical properties of welding seams was studied. It was found that, in the porthole die extrusion process of aluminum alloy profiles, fine or coarse grains and micro-voids can be formed in welding seams. Although the new grains through the bonding interface have been formed, there are still many micro-voids in these new grains. Increasing billet heating temperature and extrusion speed not only contributes to the formation of the new grains through the bonding interface, but also promotes the closure of the micro-voids on the bonding interface, and thereby improves the atomic bonding degree of the material on both sides of the bonding interface. The hardness, strength and ductility of the extruded profiles can be improved by increasing billet heating temperature and extrusion speed. [ABSTRACT FROM AUTHOR]

During the extrusion process of aluminum alloy profiles, scientific and reasonable design of extrusion dies affects directly on the product qualified rate, production efficiency, and cost. In this work, for a 7N01 aluminum alloy beam profile used in high-speed train, the response surface method (RSM) and mesh deformation technique (MDT) are applied to automatically optimize the feeder chamber of the extrusion die. With implanted material physical properties and constitutive model of this alloy, the numerical simulation of the extrusion process is firstly carried out and verified experimentally. Then, RSM is used to optimize seven different geometric variables of the feeder chamber and to narrow the variables' ranges. On the basis of above optimization, MDT is finally applied to automatically optimize the feeder chamber. After optimization, the velocity distribution in the cross section of the profile tends to more uniform. The standard deviation of the velocity field decreases from 7.83 to 2.47 mm/s with the reducing rate of 68.46%. More importantly, the automatic optimization process with mesh deformation technique is explored in this work, which could provide an effective and potential means for the automatic optimization design of three-dimensional dies or products in other fields. [ABSTRACT FROM AUTHOR]

The solid state welding process during porthole die extrusion of hollow structure aluminum alloy profiles is very important since it directly determines the microstructure and mechanical properties of welding seams in extruded profiles. In this study, the grain structure, special grain boundary and micro-texture along the welding path of an aluminum alloy profile were characterized, and the relation between the microstructure and mechanical properties of the welding seam was revealed. It was found that, along the welding path, the fine equiaxed grains around the welding line are elongated along extrusion direction under the combined action of shearing and compression, then, the elongated grains grow into the strip-shaped coarse grains by means of grain boundary migration, and finally, some strip-shaped coarse grains evolve into the fine equiaxed grains by means of continuous dynamic recrystallization and geometric dynamic recrystallization. Along the welding path, the fraction of special grain boundaries firstly increases and then decreases, while the fraction of low angle grain boundaries increases continually. The strong {111} fiber is formed in the zone near the surface of bridge, and it transforms into the very strong shear-type texture consisting of A* 1 and A* 2 components at the beginning stage of extrusion welding. Then, these shear-type texture components transform into the strong goss and copper components. Finally, the goss and copper components weaken and the weak cube texture appears in the welding zone of the extruded profile. It was also found that the increase of the low angle grain boundaries and the decrease of the average grain size in welding zone contribute to the improvement of harness, strength and fracture strain, while the existence of the strip-shaped coarse grains and different types of textures in welding zone is adverse for the improvement of welding quality. [ABSTRACT FROM AUTHOR]

Aluminum profile extrusion involves complex thermal, tribological, and mechanical interactions; thus, material flow and thermal behavior during extrusion process are very complicated. In this work, the material flow and thermal behavior of a 7 × × × aluminum alloy profile during an entire extrusion cycle are investigated numerically and experimentally. Hot compression tests are firstly carried out, and inverse analysis method is used to identify the material parameters of AA7N01 in Arrhenius constitutive model. The calculated global error is only 6.2 % between the predicted and experimental force-displacement curves, which verifies that the proposed model and obtained material parameters can describe well the rheological behavior of this alloy at elevated temperatures. Then a thermo-mechanical finite element model based on DEFROM-3D is built, and the transient extrusion process of the profile is simulated. By numerically analyzing the nose-end shape of the extruded profile, the evolution curves of exit temperature and of extrusion load, material flow and thermal behavior during extrusion process are investigated, respectively. Practical extrusion experiments verify the numerical model and results. Additional microstructure examination with electron backscatter diffraction (EBSD) technique also shows fine grains with the uniform grain size of about 9 μm on different locations of the extruded profile. Therefore, the material constitutive model and numerical model of extrusion process built in this work are capable enough to provide theoretical guidance in optimizing process parameters and designing extrusion dies. [ABSTRACT FROM AUTHOR]

Material flow uniformity in a die cavity is the key to extrude sound aluminum alloy radiators. However, it is generally difficult to control material flow due to their geometry features, such as complex cross section, multiple teeth, etc. In this work, for an irregular and multitooth aluminum alloy radiator, the initial extrusion die is firstly designed. Numerical simulation and experimental observation both show that the extruded radiator could not meet the size and shape requirements due to severe twist deformation in the cross section. Then, four different die modifications (resizing the porthole structure, chamfering the mandrel support, adding baffle plates, and adjusting bearing lengths) are taken to improve material flow uniformity during the extrusion process. Through a series of die modifications, the velocity difference in the cross section of the radiator is reduced from 34.9 mm/s with the initial extrusion die to 8.3 mm/s with the modified one. The standard deviation of the velocity field in the cross section decreases from 10.7 to 3.3 mm/s, and the velocity uniformity is improved greatly. With the modified extrusion die, a sound radiator is extruded with the desired size and geometry. Finally, the extrusion die modification rules are summarized for this kind of radiators. [ABSTRACT FROM AUTHOR]

Solid-state bonding is an important problem in hot extrusion process of aluminum alloy profiles, especially for hollow section profiles. Predicting and decreasing the length of transverse weld seam (T-seam), improving the solid-state bonding degree and controlling microstructure of longitudinal weld seam (L-seam) are major concerns. In this work, a set of porthole extrusion dies with different shapes of legs (pointed and square) and depths of welding chambers were designed and manufactured. A series of extrusion experiments for different die structure parameters were performed, and microstructure observations, tensile tests and fracture feature analyses for the extruded profiles were conducted. The influences of the shapes of legs and the depths of welding chambers on the evolution and the length of T-seams and on the formation, microstructure and mechanical properties of L-seams were respectively investigated by means of experiment and numerical simulation. The distribution law of the ratio of pressure to material flow stress, p/σ , and the material flow behavior in welding plane were studied by using numerical simulation method. The results showed that the profiles extruded by the dies with pointed legs have single-convex T-seams and straight L-seams on their cross sections, and their T-seams are relatively shorter but their ductility is relatively inferior. While, the profiles extruded by the dies with square legs have double-convex T-seams and cross-shaped L-seams, their ductility is relatively superior but their T-seams are longer. With the increase of the depth of welding chamber, the ductility of the extruded profiles is increased, but the lengths of T-seams are almost invariable. In addition, it was found from numerical simulation results that, in the welding plane, the deforming material with a higher flow velocity has a lower value of p/σ , and vice versa. It was concluded that an effective welding zone should exist in the welding plane, and the deforming material only in this effective welding zone can flow into the extrusion die bearing to form an L-seam in extruded profile. [ABSTRACT FROM AUTHOR]

The isothermal hot compression tests of as-cast and homogenized 2024 aluminum alloy were carried out under wide range of deformation temperatures (623-773 K) and strain rates (0.001-10 s). The constitutive equations for both initial states were established based on Arrhenius model, and the processing maps were constructed based on the dynamic material model. The results show that the flow stress of samples is evidently affected by both the strain rate and deformation temperature, and the flow stress in homogenized state is always higher than that in as-cast state. Through calculating the correlation coefficient ( R) and average absolute relative error of the established constitutive equations, it indicates that Arrhenius model can only provide a rough estimation on the flow stress. However, a much more precise value of the flow stress was obtained by introducing the strain compensation into Arrhenius model, since the effects of strain on the material constants were well considered. Furthermore, according to the processing maps, a suggested range of deformation temperature and strain rate for hot forming process were given then: temperature range 710-773 K and strain rate range 0.001-1 s for as-cast state, and temperature range 680-773 K and strain rate range 0.003-0.22 s for homogenized state. [ABSTRACT FROM AUTHOR]

During the extrusion process of aluminum alloy, the ram velocity should be well controlled, since it is an important parameter affecting the profile quality and extrusion productivity. The effects of ram velocity on conventional porthole die extrusion have been investigated by some researchers, while its influence on pyramid die extrusion has not been fully clarified. Thus, in this study, the pyramid die extrusion process for producing a hollow rectangular aluminum tube was comprehensively investigated by performing analysis of steady state, transient state, and billet skin tracking. Importantly, the effects of ram velocity on some evaluation parameters of pyramid die extrusion, such as the material flow behavior, extrudate temperature, extrusion force, transverse weld, quality of longitudinal weld, and back end defect, were overall investigated. The results show that the flowing velocity, extrudate temperature, extrusion force, and welding pressure tend to increase as the increase of ram velocity, while the length of transverse weld is reduced at higher ram velocity. However, the effect of ram velocity on the back end defect is quite slight. Moreover, the advantages and shortcomings of pyramid die were also discussed by comparing with the conventional porthole die. [ABSTRACT FROM AUTHOR]

The isothermal hot compression tests of homogenized 6026 aluminum alloy under wide range of deformation temperatures (673–823 K) and strain rates (0.001–10 s − 1 ) were conducted using Gleeble-1500 thermo-simulation machine. According to the experimental obtained true stress–strain data, the constitutive equations were derived based on the original Johnson–Cook (JC) model, modified JC model, Arrhenius model and strain compensated Arrhenius model, respectively. Moreover, the prediction accuracy of these established models was evaluated by calculating the correlation coefficient ( R ) and average absolute relative error (AARE). The results show that the flow behavior of homogenized 6026 aluminum alloy is significantly affected by the strain rate and temperature. The original JC model is inadequate to provide good description on the flow stress at evaluated temperatures. The modified JC model and Arrhenius model greatly improve the predictability, since both of these models consider the coupled effects of deformation temperature and strain rate. However, to give more precise description, the influence of strain on the material constants should be introduced into Arrhenius model. [ABSTRACT FROM AUTHOR]

Although the extruded profiles of 7005 aluminum alloy have been widely used in the components of high speed train, automobile and aircrafts, the plastic deformation behavior of homogenized 7005 aluminum alloy at evaluated temperature has not been fully clarified. In this study, the isothermal hot compression tests of homogenized 7005 aluminum alloy at the deformation temperatures ranging from 623 K to 823 K and with the strain rates ranging from 0.001 s −1 to 10 s −1 were conducted for constitutive analysis. It was found that the flow stress increased with decreasing deformation temperatures and increasing strain rates. Two Arrhenius-typed constitutive equations without and with the compensation of strain were developed based on the true stress–strain curves. Although both constitutive equations show their excellent predictability on the flow stress, the one considering the influence of strain has higher accuracy. Furthermore, the extrusion experiment and corresponding finite element simulation using the developed constitutive equation with strain compensation were carried out. The simulated results confirmed that the material flow behavior of the 7005 aluminum alloy during extrusion process was well predicted. [ABSTRACT FROM AUTHOR]

During the warming forming process of aluminum alloys, both temperature and strain rate have significant influences on sheet formability. However, current research regarding the effects of temperature and strain rate on the forming limit curves of aluminum alloys is still lacking. Due to the difficulty in carrying out the experiments for obtaining forming limit curves under dynamic forming conditions at elevated temperature, in this work, the method is proposed to investigate these effects by combining a modified Voce constitutive model (Lin-Voce model) with the numerical simulation of Marciniak test. On the basis of experimental data obtained by the tensile tests, the material parameters of Lin-Voce model are identified by the inverse analysis technique. Then, the proposed Lin-Voce model is verified by comparing numerical and experimental results obtained by Marciniak test. Finally, the numerical simulation of Marciniak test is carried out at different temperatures (100, 200 and 300 °C) and punch speeds (10, 750 and 1000 mm/s), and the effects of temperature and strain rate on the forming limit curves of AA5086 are investigated and discussed. [ABSTRACT FROM AUTHOR]

Second-step welding chamber of porthole die plays an important role in controlling metal flow and improving the quality of the extrudate. In this article, using a condenser tube aluminum alloy extrusion profile as the example, the shape and the height of second-step welding chamber of the extrusion die are selected as the design variables. Standard Deviation of the Velocity field in bearing exit (SDV) is used as the objective function. By combining Box–Behnken experimental Design (BBD) with Response Surface Method (RSM), a prediction model for SDV is established. The model is optimized by means of genetic algorithm (GA), and the optimal extrusion die for the condenser tube profile is obtained. In comparison with the initial die design, a more uniform velocity distribution in the cross-section of the profile in the bearing exit is achieved by using the optimal die design. The SDV is reduced from 4.37 mm/s of the initial die design to 0.29 mm/s of the optimal die design. The distortion of the extrudate is controlled effectively. Thus the extrudate quality is improved significantly, and its shape and dimension are satisfactory. Finally, the metal flow pattern and die strength for the optimal scheme are analyzed. The optimization strategy proposed in this article has practical meaning in improving the die design, shortening the production development cycle, and reducing the production cost. [ABSTRACT FROM AUTHOR]

Currently, with the increasing demand of high production output, much attention is paid to the research and development of multi-hole extrusion die. However, owing to the complexity of multi-hole porthole extrusion technology, it has not been applied widely in practice for the production of aluminum profiles, especially for porthole die with an odd number of die orifices. The purpose of this study is to design a three-hole porthole die for producing an aluminum tube and to optimize the location of die orifices based on computer-aided design and engineering. First, three-hole extrusion dies for different locations of die orifices are designed. Then, extrusion processes with different multi-hole porthole dies are simulated by means of HyperXtrude. Through numerical simulation, metal flow, temperature distribution, welding pressure, extrusion load, and die stress, etc. could be obtained, and the effects of the location of die orifices on extrusion process are investigated. With the increasing distance between die orifice and extrusion center (described as eccentricity ratio), metal flow becomes nonhomogeneous, and twisting or bending deformation of profile occurs, but the welding pressure rises, which improves the welding quality of profiles. However, the required extrusion force, billet and die temperature, die displacement, and stress induce no significant changes. In comparison with the extrusion force during single-hole porthole extrusion, there is 18.5% decrease of extrusion force during three-hole porthole extrusion. Finally, design rules for this kind of multi-hole extrusion dies are summarized. [ABSTRACT FROM AUTHOR]

In this article, a subroutine that calculates die wear depth based on modified Archard's wear model was developed and then embedded into DEFORM-3D, with which the extrusion process of an aluminum alloy 7075 rod was simulated. Useful information was obtained from the numerical simulation, including interface pressure, distribution of instantaneous temperature, required extrusion force, die wear depth, etc. The numerical result shows that extrusion parameters have multiple effects on die wear behavior. The severest die wear occurs at the bearing entrance due to the greatest deformation, highest pressure, and temperature in this area. It is found that ram speed has no single tendency on die wear, while die wear depth rises with the elevated initial temperatures of billet and extrusion tooling. In addition, the required extrusion force has strong dependence on extrusion parameters. The extrusion force rises clearly with an increase of ram speed and a decrease of initial temperatures of billet and extrusion tooling, which is totally accordant to practical observation. Therefore, the study in this work could provide useful and helpful guides for selecting reasonable extrusion variables, predicting die life and reducing production cost. [ABSTRACT FROM PUBLISHER]

Purpose – The paper aims to use the finite volume method widely used in computational fluid dynamics to avoid the serious remeshing and mesh distortion during aluminium profile extrusion processes simulation when using the finite element method. Block-structured grids are used to fit the complex domain of the extrusion. A finite volume method (FVM) model for aluminium extrusion numerical simulation using non-orthogonal structured grids was established. Design/methodology/approach – The influences of the elements' nonorthogonality on the governing equations discretization of the metal flow in aluminium extrusion processes were fully considered to ensure the simulation accuracy. Volume-of-fluid (VOF) scheme was used to catch the free surface of the unsteady flow. Rigid slip boundary condition was applied on non-orthogonal grids. Findings – This paper involved a simulation of a typical aluminium extrusion process by the FVM scheme. By comparing the simulation by the FVM model established in this paper with the ones simulated by the finite element method (FEM) software Deform-3D and the corresponding experiments, the correctness and efficiency of the FVM model for aluminium alloy profile extrusion processes in this paper was proved. Originality/value – This paper uses the FVM widely used in CFD to calculate the aluminium profile extrusion processes avoiding the remeshing and mesh distortion during aluminium profile extrusion processes simulation when using the finite element method. Block-structured grids with the advantage of simple data structure, small storage and high numerical efficiency are used to fit the complex domain of the extrusion. [ABSTRACT FROM AUTHOR]

The extrusion die plays a crucial role in the quality control of aluminum alloy profile production. In practice, the extrusion die design mainly depends on the experience and intuition of the die designers. The designed and manufactured dies are usually tested and modified many times before putting into practical extrusion production, and difficult to be guaranteed as optimal ones. In this paper a method of die design based on numerical simulation was proposed in order to optimize the die structure and enhance the level of die design. Firstly, the extrusion process of a large wallboard of high-speed train was simulated by means of HyperXtrude software. It was found that a severe non-uniform velocity distribution emerged in the cross-section of the extrudate and twist deformation occurred, therefore the initial die was not an acceptable one. Then, three times of modifications to the die structure were made to optimize the die structure and improve the product quality. Finally, an optimal die structure with uniform material flow velocity in the cross-section of the die exit was obtained. A sound wallboard extrudate of high-speed train was produced. The die design methods for complex extrusion profiles were summarized and proposed, including the design methods of porthole area of multi-cavity dies, the baffle plate, and the sunken port bridge structure. [ABSTRACT FROM AUTHOR]

Abstract: The most popular numerical method used for simulating aluminum alloy extrusion process is finite element method (FEM). But aluminum alloy profile extrusion process is a metal forming process with severe and large plastic deformation. If finite element method is used to simulate aluminum profile extrusion process, mesh always distorts quickly and frequent remeshing is needed. In addition, the checks for node-separation-from or node-contact-to die surfaces are also frequently needed. The continuous remeshing and node-separation-contact checks usually decrease the accuracy of FEM-based simulation results and increase the CPU time. In this paper, finite volume method (FVM) based on Euler mesh is used to simulate three-dimensional steady or transient aluminum alloy profile hot extrusion process. Semi-implicit method for pressure-linked equations (SIMPLE) algorithm is used to calculate the velocity field and the pressure field of the extrusion process. The dynamic viscosity coefficient of the material mostly dependent on temperature and the effective strain-rate is updated in every SIMPLE inner iteration. At every exterior time step, the method of volume of fluid (VOF) is applied to catch the transient free surface of the material. “Moving grids system” is also used to deal with the moving problem of the boundaries of the calculated domain caused by the moving of the extrusion ram. To ensure the stability and efficiency of the simulation, automatic adjustment of the time increment is realized. Two typical extrusion processes are simulated by the FVM model of this paper. Some results are compared with those simulated by FEM. The material flow characteristics from transient state of extrusion process to steady state of extrusion process are also discussed. [Copyright &y& Elsevier]

Abstract: Bulk ultra-fine-grained materials can be obtained by equal channel angular pressing (ECAP) process. A new metal forming process called as continuous confined strip shearing (CCSS/C2S2) process based on ECAP and Conform process was introduced in this paper for fabricating aluminum alloy sheets with a high formability. The C2S2 process was simulated numerically by using DEFORM-3D and the deformation behavior of the pure aluminum sheets was studied. The influences of die geometric parameters such as the die channel angle and the die outer corner angle on the material deformation were given. In addition, the effect of the friction on the die–workpiece interface on the effective strain change in the C2S2 process was investigated. The obtained numerical simulation results provide valuable guidelines for C2S2''s die design, determination of process parameters and process planning. [Copyright &y& Elsevier]

Abstract Al/Mg/Al sheet was fabricated by the proposed porthole die co-extrusion and subsequent hot rolling (PCE-R) method. The intermetallic compounds of β-Al 3 Mg 2 and γ-Mg 17 Al 12 were formed in transition layer after PCE-R process, and the thicknesses of β and γ layers became larger at higher rolling temperature or higher reduction ratio. Partial dynamic recrystallization (DRX) occurred in Al layer, and Al layer mainly consisted of shear-typed {111} fiber textures. However, if the rolling reduction is as high as 75%, Al layer exhibited quite different texture components. Mg layer consisted of fine equiaxed grains and several elongated grains, implying the occurrence of near complete DRX. With the increase of rolling temperature or reduction ratio, the number of Mg 17 Al 12 particles in Mg layer was reduced, resulting into larger grain size. Mg layer had strong basal plane texture with c -axis parallel to transverse direction. Al/Mg/Al sheet rolled at 300 °C with 65% reduction exhibited two stress-drop fracture mechanism during tensile test, and it showed excellent tensile strength of 149 MPa, and elongation of 0.13. However, Al/Mg/Al sheet rolled with 75% reduction had inferior tensile properties due to the existence of some cracks after rolling. Graphical abstract Image 1 Highlights • Porthole die co-extrusion and hot rolling was proposed for fabricating Al/Mg/Al sheet. • Thickness of intermetallic compounds increased with increasing rolling temperature and reduction ratio. • Rolling temperature and reduction ratio affected the microstructure of both Al and Mg layers. • Al/Mg/Al sheet rolled at 300 °C with 65% reduction exhibited best tensile properties. [ABSTRACT FROM AUTHOR]

Abstract A reasonable constitutive model is the key for accurate numerical simulation of extrusion process of aluminum alloy profiles. In this work, 20 material parameters in a fourth-order strain-compensated constitutive model of an Al-Zn-Mg alloy were determined by the inverse analysis method. Firstly, taking the minimization of shape error of specimens under different compression extents (10–60%) at the temperature of 475 °C and the strain rate of 1 s−1 as the optimization objective, the friction coefficient in hot compression test was determined by inverse analysis. Results showed that the friction coefficient was 0.031 and the global error was merely 1.001%, which demonstrated the practical lubrication condition between specimen and tool head could be reflected by the acquired friction coefficient. Then, based on the obtained friction coefficient, the inverse analysis was also used to identify 20 unknown material parameters in the fourth-order strain-compensated constitutive model at once by minimizing the difference between predicted and experimental force-displacement data. The predicted force-displacement curves matched the experimental ones well with the global error of only 6.07%. Finally, the developed constitutive model was applied in simulating the porthole and piercing extrusion for a hollow thin-walled profile and corresponding verified experiments were also carried out. Graphical abstract fx1 Highlights • 20 material parameters were identified at once for AA7N01 by inverse analysis. • The friction coefficient in hot compression was obtained as 0.031 by inverse analysis. • The constitutive model was successfully applied and verified in the profile extrusion. [ABSTRACT FROM AUTHOR]

In this study, the dynamic recrystallization (DRX) behavior of an Al-Zn-Mg alloy during porthole die extrusion process was studied. Firstly, the hot compression tests were conducted at varied temperatures and strain rates. The constitutive equation was established based on modified Arrhenius and Johnson-Cook models, respectively, and DRX kinetic equation was established based on modified Avrami model. Secondly, transient simulation using the established constitutive and DRX kinetic equations was performed for porthole die extrusion process. Finally, in order to verify the accuracy of simulated results, the extrusion experiment was conducted and the microstructure was analyzed. The results show that both the strain compensated Arrhenius model and modified Johnson-Cook model can accurately describe the flow stress of Al-Zn-Mg alloy at elevated temperature. Higher deformation temperature and lower strain rate are favorable for the occurrence of DRX. The volume fraction of DRX at the zones close to bridge and porthole wall is much higher than that in the other zones, and this kind of inhomogeneous DRX behavior is mainly attributed to varying distribution of stain. According to the experimental results, several subzones with different microstructures were identified. Importantly, the simulated DRX volume fraction shows good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Self-pierce riveting (SPR) has been widely applied to join carbon fiber-reinforced polymer (CFRP) composites and high-strength metallic plates in the automotive and aerospace fields. However, the CFRP is often damaged by rivet piercing owing to its brittleness as well as the relatively small interlocking that forms between the rivet leg and high-strength plate owing to the hard deformation characteristics. Therefore, in this study, a novel low-frequency vibration-assisted self-pierce riveting (LV-SPR) technology is proposed, which utilizes the vibration effect in softening the metal and reducing interfacial friction at room temperature. In riveting experiments involving CFRP and 5052 aluminum alloy utilizing 37Cr4 semi-hollow rivets, LV-SPR exhibited a significant reduction of 68.2% in the riveting force compared to the traditional SPR process. The decreased riveting pressure in LV-SPR effectively mitigated the CFRP damage by 36.2%, which was caused by a reduction in the interfacial friction force between the rivet and CFRP laminate. Moreover, owing to the improved deformation capacity of the rivet and alloy plate by the vibration softening effect, the lateral expansion of the rivet leg in the aluminum alloy was enlarged by 36.4% compared to that using the traditional self-piercing riveting (T-SPR) process. Microscopic characterization revealed that vibrations notably promoted grain refinement and enlarged the subgrain structures of the rivets and alloy plates. Finally, by superposing oscillations, the shear strength of the connection joint increased by 13.5% compared to the T-SPR joint. The proposed LV-SPR was validated as an effective technique to increase the connection strength of high-performance plates, which can efficiently improve the structural safety and promote the widespread application of CFRP/alloys in automobiles and aircrafts. [Display omitted] • LV-SPR process is proposed for joining CFRP and high-strength Al alloy plates. • Interlock and joint strength are greatly improved by vibration softening effect. • LV-SPR reduces the interfacial friction resulting in diminished CFRP damage. • Grain refinement brought by vibration enhances joint hardness and strength. [ABSTRACT FROM AUTHOR]

The solution experiments on cold rolled 2024 Al sheet with a 1070 Al coating were carried out at various temperatures and holding time. The effects of solution parameters on the microstructure evolution and mechanical properties were studied. The results showed that the alloying elements diffused from the 2024 Al matrix to the 1070 Al coating, following the peak-valley pattern. The cold rolled 2024 Al sheet mainly have the second phases of Al 2 Cu, S (Al 2 CuMg), Si, Mg 2 Si, and the impurities of AlFeMnSi, AlCuFeMnSi, AlCuFeMn, and the amount of them was reduced with increasing solution temperature or holding time. T (Al 20 Cu 2 Mn 3) had precipitated before aging, and only the Cu–Mg clusters were formed during the natural aging, which should be the main strengthening mechanism. The grain structure was elongated during cold rolling, while the static recrystallization and grain growth occurred during the solution treatment. The ultimate tensile strength, yield strength and elongation were gradually enhanced with increasing the solution temperature to 510 °C. When the solution temperature is further increased to 530 °C, the elongation was obviously decreased due to the over-burning. Moreover, it was found that the solution temperature had much stronger effects on the mechanical properties than that of the holding time. Image 1 • Effects of solution parameters on naturally aged EN AW 2024 Al sheet were studied. • Most of the second phases dissolved during solution, while the Fe containing phases were remained. • High solution degree facilitated the formation of Cu–Mg clusters during natural aging. • UTS, YS and elongation of naturally aged 2024 Al reached the peak values after solution treated at 510 °C. [ABSTRACT FROM AUTHOR]

Lattice defects significantly affect the mechanical performance of metallic materials. In this study, lattice defects of a carbon nanotube reinforced 2024 aluminum alloy (CNT/2024Al) composite were systematically investigated and the contribution of carbon nanotubes was illustrated. The results showed that dislocations and grain boundaries were closely related to the deformation behavior and lead to discontinuous yielding phenomena. Moreover, the carbon nanotubes reduced the stacking fault energy, which was conducive to forming stacking faults and a small number of twins in the composite. The stacking faults, twin boundaries, and intragranular Al 4 C 3 phases hindered dislocation motion, thus enhancing the mechanical properties of the composite. In addition, the novel formation mechanism of the 9R structure was revealed: the Σ 3 (1 1 ‾ 1) / (151) incoherent twin boundary may dissociate into two tilt walls bounding a 9R structure (zone axis: [ 1 ‾ 01 ]), which enriches understanding of the relationship between Σ 3 twin boundaries and the 9R structure. [Display omitted] • The discontinuous yielding phenomenon of a CNT/2024Al composite is clarified. • Stacking faults, twins and 9R structure are observed in CNT/2024Al composite. • Deformation twins can be induced by MAP and SAP twinning. • The Σ 3 (1 1 ‾ 1) / (151) incoherent twin boundary dissociates into two tilt walls, with the intermediate 9R structure. [ABSTRACT FROM AUTHOR]

The extrusion parameters greatly influence the microstructures of aluminum alloys, and further determine the mechanical properties of the final products. In this work, using a self-designed experimental device, a series of extrusion experiments was conducted to investigate the influence of the extrusion parameters on the microstructure, crystallographic texture, and second-phase particles in the Al-Mg-Si aluminum alloy (AA6N01), which is widely applied in the bodies of high-speed trains. Firstly, the billet discard in the press container was taken out for analyzing the material flow and microstructural evolution during the extrusion process. The results showed that continuous dynamic recrystallization occurred, and the initially coarse equiaxed grains in the as-homogenized billet evolved gradually into fine equiaxed grains at the die exit due to their dynamic recovery and dynamic recrystallization. More importantly, coarse grain layers were observed on the surface of the extruded profiles under specific extrusion conditions (460 °C/48 mm/min and 520 °C/48 mm/min). Then, the textures on the surface and at the center of the profiles were analyzed under different extrusion conditions by electron backscatter diffraction. The results showed that the textures of all the extruded profiles were mainly along <100> and <111 > , but the texture intensity was higher at the profile's center than that on the surface under the same extrusion condition. Finally, the second-phase particles in the as-homogenized billet and as-extruded profiles were compared and analyzed. The Fe-rich particles were broken under deformation conditions and their sizes decreased during the extrusion process. However, they were all still distributed on the grain boundaries after deformation, and the composition and content remained unchanged. The Mg 2 Si particles served as the main strengthening phase in AA6N01, and they were greatly aggregated as the extrusion temperature increased and the extrusion speed decreased. [ABSTRACT FROM AUTHOR]

Abstract The dynamic recrystallization (DRX) behavior and microstructure evolution of an Al-Mg-Si aluminum alloy (AA6N01) during hot deformation are investigated by experiments and mathematical modeling. Based on hot compression tests under different strain rates and temperatures, the type of dynamic recrystallization are firstly investigated by EBSD analysis. It is observed that DRX occurs under all examined conditions, however, the type of DRX is associated with the deformation temperature at the strain level of about 1.5. Then considering the deformed and recrystallized behaviors, a grain size evolution model is established to predict the microstructure evolution during hot deformation. (1) According to the dislocation work hardening theory, the DRX kinetic model is built to predict the distribution of DRX. (2) Taking the effects of deformation temperature and strain rate into account, the DRX grain size model is built to predict the equiaxed recrystallized grain size. (3) By combining the experimental observations with numerical simulation, the deformed grain size model is established to predict the elongated grain size evolution. Finally, by integrating above three models, the grain size evolution model is established to predict the microstructure evolution of AA6N01 during high-temperature deformation and is validated by comparing the predicted grain size with experimental observations during hot compression and hot extrusion, respectively. Graphical abstract Image 1 Highlights • Eight material parameters of a physical constitutive model are identified for AA6N01. • The type of DRX of AA6N01 depends highly on the deformation temperatures. • A grain size evolution model is established to predict the microstructure evolution. • The bulit grain evolution model is well validated by hot compression and extrusion. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of 1060/6063 Al alloys joint fabricated by porthole die extrusion were investigated. A sound welding interface of 1060/6063 Al alloys was obtained, and the welding quality can be further improved using higher welding chamber. Complete dynamic recrystallization (DRX) occurred during porthole die extrusion, while the DRXed grain size of 6063 Al matrix was always much smaller than that of 1060 Al matrix. The height of welding chamber had an significant effects on the microtexture of the extruded profiles. The profiles extruded using welding chamber with a height of 10 mm exhibited highest tensile strength and elongation. On the contrary, the joining of 1060/6063 Al alloys using flat die is not acceptable, where many cracks appeared at the welding interface and only partial DRX occurred. [ABSTRACT FROM AUTHOR]

This work investigates the transverse weld in 7N01 aluminum alloy hollow profile used in high-speed train by experimental analysis coupled with finite element simulation. The macroscopic morphology and the evolution of transverse weld were obtained by extrusion experiments and the corresponding microstructure and texture were analyzed with EBSD. Significant differences in grain size, grain orientation and texture content on both sides of transverse weld were found. The content of recrystallization texture in the old billet was larger than that in the new billet, and the grain sizes in the old billet were smaller than those in the new billet. In order to analysis the evolution of transverse weld and reduce the length of transverse weld, the numerical model of transverse weld was then built with HyperXtrude and was verified by comparing with experimental observations. The influences of extrusion process parameters and die structure on the length of transverse weld were studied systematically by using the established transverse weld model. The transverse weld length was reduced effectively by adjusting the extrusion ratio, ram speed, height of baffle plate, corner radius of welding chamber and sinking depth of port bridge. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Al/Ti composite bar obtained by a novel continuously-extruded technique exhibits a superior strength-ductility balance. • A nanocrystalline Al layer is generated at the interface, accompanying with the precipitation of Mg-/Si-enriched clusters. • Nanoscale TiAl 3 grains are nucleated on the Ti/TiAl 3 interface, inducing the formation of misfit dislocations. • The dislocation-interface interaction and constraint effect are triggered on the 3D interface during deformation. In this work, a novel extrusion die for embedding the continuous Ti wire into the aluminum alloy is developed, and the extruded composite bar is obtained. The multi-scale interface structure, elemental diffusion, and mechanical characteristics are investigated by different material characterization methods. The three-dimensional (3D) amorphous regions are produced on the well-bonded Al/Ti interface. The formation of a nanocrystalline Al layer is accompanied by the precipitation of Mg-/Si-enriched clusters. With an increase in the annealing time, the average grain size of TiAl 3 increases, while the dislocation density of the TiAl 3 layer decreases. A nanoscale TiAl 3 monolayer is exhibited between the Al/TiAl 3 and Kirkendall interfaces, whereas two types of nanoscale TiAl 3 grains are detected on the Ti/TiAl 3 interface. The Si-enriched clusters are aggregated at the Ti/TiAl 3 interface, generating a nanoscale layer. Local inhibition behaviors of large-sized Mg-enriched clusters on the growth of TiAl 3 are observed at the Al/TiAl 3 interface after annealing for 48 h. Not only are massive misfit dislocations and distorted lattices detected on the 3D interface, but also locally ordered transition zones are noticed. The extruded composite bar exhibits a superior strength-ductility balance, which provides a new strategy for the development of aluminum profiles. [ABSTRACT FROM AUTHOR]

In this work, a two-stage inverse analysis technique is proposed to identify the friction coefficients during hot compression test of aluminum alloy 6N01 (AA6N01) and its material parameters in the strain-compensated Arrhenius-type constitutive model. Firstly, the minimal shape error between the measured and simulated specimen is set as the optimization objective. Based on the material parameters obtained by a traditional linear fitting method, the friction coefficient under each forming condition is obtained by the first-stage inverse analysis method. Secondly, on the basis of the obtained friction coefficients and taking the minimal error between the experimental and predicted forces as the optimization objective, 16 unified material parameters in the constitutive model are identified by the second-stage inverse analysis method. Then above two stages are combined together to realize loop calculation: the first-stage inverse analysis provides friction coefficients for the identification of material parameters while the second-stage updates new material parameters for identifying better friction coefficients. When the average error ( E r (friction)) between friction coefficients obtained at the current and last loop is less than 5%, the whole identification process comes to the end and the optimized friction coefficients and material parameters are obtained. Results show that the maximum shape error is only 2.48%, which indicates that the obtained friction coefficients can reflect the practical lubrication conditions between the tooling head and specimens. Additionally, at low strain rates (0.01, 0.1 and 1 s −1 ), the predicted forces have a good agreement with experimental ones. While at high strain rate (10 s −1 ), some discrepancy exists between the predicted and experimental results and the maximum error arrives at 8.58%. But the global predicted error is only 4.2%, which verifies that the proposed model and obtained material parameters can describe well the rheological behavior of AA6N01 at elevated temperatures. By comparing the predicted forces obtained by the inverse analysis and traditional linear fitting method, it is found that the predicted forces by the inverse analysis are more close to experimental data. Therefore, it can be concluded that more accurate material parameters can be obtained and provided for the numerical simulation of the extrusion process of AA6N01 using the two-stage inverse analysis technique proposed in this paper. [ABSTRACT FROM AUTHOR]

This paper proposes a method to investigate the effects of temperature and strain rate on the forming limit curves (FLCs) by combining a modified Voce constitutive model (Lin-Voce model) with the numerical simulation of Marciniak test. The tensile tests are firstly carried out at different forming temperatures (20, 230 and 290 °C) and strain rates (2.5, 120 and 150 s −1 ) for AA5086 sheet. A modified Voce constitutive model (named Lin-Voce model) is proposed to describe the deformation behavior of AA5086 and its material parameters are identified by inverse analysis technique. Then, the proposed constitutive model is verified by comparing numerical and experimental results obtained by tensile tests and Marciniak test, respectively. Finally, the numerical simulation of Marciniak test is carried out at different temperatures (100, 200 and 300 °C) and strain rates (2.5, 120 and 150 s −1 ), and the effects of temperature and strain rate on the FLCs of AA5086 are investigated and discussed. [ABSTRACT FROM AUTHOR]