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Predicted temperature evolution during the extrusion at a ram speed of 6 mm/ s and at various ram displacements "S… in both the transient state and the steady state
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At present, a fundamental knowledge of the thermal and mechanical interactions occurring during the extrusion of magnesium is lacking. This acts as a serious technological barrier to the cost-effective manufacturing of lightweight magnesium alloy profiles. In the present research, a three-dimensional finite element (FE) simulation of extrusion to p...
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Experimental measurements are used to characterize the anisotropy of flow stress in extruded magnesium alloy AZ31 sheet during uniaxial tension tests at temperatures between 350°C and 450°C, and strain rates ranging from 10-5 to 10-2 s-1. The sheet exhibits lower flow stress and higher tensile ductility when loaded with the tensile axis perpendicul...
Citations
... The finite element simulation results revealed that the most crucial process parameter is the number of holes and their locations on the extrusion die. Liu et al. [7,8] used finite element simulation to investigate the effects of ram speeds and billet temperatures on the extrusion load in magnesium alloy AZ31 extrusion with an X-shaped cross-section. The correlations between the process variables and the response of the extrusion temperature and the peak extrusion pressure were established from the finite element simulations and verified by experiments. ...
Hollow tubes are generally manufactured using porthole die extrusion. A finite element software QForm is used to analyze the material flow of aluminum alloy A6061 tubes inside a specially designed porthole die during tube extrusion. High welding pressure and shorter transverse seam length are required for a sound product. Various extrusion conditions and die geometries and dimensions affect the bonding strength of the products. In this paper, the effects of die geometries on the welding pressure are discussed using the Taguchi method. The simulation results show that a higher welding pressure is obtained with a larger porthole radius, a larger welding chamber height, and a larger bearing length, while a larger bridge width increases the welding pressure slightly. For transverse seam lengths, a shorter transverse seam length can be obtained with a smaller porthole radius and a smaller welding chamber height, and a shorter bridge width and bearing length decrease the transverse seam length slightly. The transverse seam region and flow patterns are observed. Tube expanding tests were also conducted. From the expanding test results, it is known that the fracture position did not occur at the welding line and the bonding strength could reach up to 160 MPa.
... For example, it is assumed that the Mg-Zn-Zr alloy is thermoplastic and the temperature limit is defined by the FE for precision reverse extrusion. A two-dimensional finite element method is used to determine the size and capability of a press for extruding a magnesium-aluminum-zinc alloy in a temperature range [7]. In addition, the behavior of the AZ31 alloy in the extrusion forming process is predicted by the real-rigid plastic material model, and the heat exchange between the workpiece and the extrusion die is included [2].The variation of the grain size of the cross-section of the extruded sheet is explained by the stress and strain distribution. ...
This paper presents a new forming technology for manufacturing the AZ31 magnesium alloy thin-wall tube. The direct extrusion process and continuous shearing-bending process are combined to produce thin-wall magnesium tube, abbreviated as “TESB” (tube extrusion-shearing-bending). The process has been studied based on the combination of experiments and numerical simulations, and the influences of temperatures, extrusion stresses, and friction factors on the forming process have been studied by Deform-3D simulation. And the mechanical properties and the grain size of the formed product have been tested. TESB technology has been proved to refine the grains of magnesium alloy tube effectively, and the mechanical property of the product can be improved. The better experimental extrusion conditions were also obtained by simulation, and the properties of the products under the condition of lubrication were better when the temperature was 400°C. Three-dimensional finite element modeling is used to investigate the plastic deformation behaviors of wrought magnesium alloy during TESB process. Numerical results indicate TES could increase the cumulative strains effectively by direct extrusion and additional shearings. Experiments show that microstructures of magnesium alloy fabricated by TESB process can be refined to 50% of the original grain size with more uniform distribution. TES process could improve hardness of magnesium alloy obviously by comparing with which fabricated by direct extrusion.
... The optimal choice of the parameters can result in a good end product. Among these parameters, the most important parameter is the extrusion temperature since the initial billet temperature is different from the actual extrusion temperature during the cycle process [2]. It is reported that temperature variation depends on initial billet temperature, flow stress vs. strain at specific temperature and strain rate, plastic deformation, friction, and heat conduction between billet with die and mandrel as well as heat convection between ambient surrounding with die and mandrel [3]. ...
... Figure 9a shows when the billet moves to the deformation zone, it starts rising with increasing friction between the billet and the die and the billet and the mandrel. Because of the severe shear, the maximum temperature appears at the junction of the die bearing and the face of die [2]. The temperatures of the billet near the die face always increase at along the die bearing surface during the subsequent steadystate extrusion. ...
The control of hot extrusion process is a highly complicated task due to high deformation and high billet temperature during the process. A high-quality product can be produced by controlling the process temperature. In this present study, hot extrusion process of hollow tube is modeled by finite element method. Effects of process parameters, initial billet temperature, ram displacements, reduction of area, semi-die angle, and friction coefficients are studied. Finite element results are compared with the experimental results from previous studies. The results reveal that there is a good agreement between simulations and experiments. It is determined that reduction of area and friction coefficient have strong effects on surface temperature and extrusion force. The surface temperature is increased with increasing ram displacement and decreased gradually at the exit of the die due to heat transfer with the environment. Extrusion forces are increased up to friction coefficient of 0.35 for 13 and 25% reduction of areas. However, extrusion forces are not changed significantly after 0.2 coefficient of friction for 37 and 48% reduction of areas.
... λ is the extrusion ratio, R1 is the billet radius 14 . The parameters were substituted into Equation 3 the Equation 4 is obtained [15,16] . ...
To explore the deformation mechanisms of a new composite extrusion including extrusion and successive shear subsequently which is shorten "ES", Three dimensional finite element modeling of grain refinements for magnesium alloys by ES process has been researched. The ES die have been designed and manufactured and installed to the horizontal extruder. Finite element software DEFORMTM-3D to investigate the plastic deformation behaviors of magnesium alloy during extrusion-shear has been employed. The extrusion loads and temperatures distribution of billets and maximum extrusion forces have been obtained from simulation results. From the simulation results it is clear that evolutions of extrusion loads curve and effective stresses and temperatures can be divided into three stages. ES process has been applied to fabricate AZ31 magnesium alloy rod at preheat temperature of 420ºC with extrusion speed of 20 mm/s. The results proved that the ES process is a formality method for magnesium suitablefor large scale industrial application. The microstructures of AZ31 magnesium alloy along the longitudinal section of rods have been sampled and examined and observed. Fine grained microstructures can be observed throughout longitudinal section of extruded rod. The researches results show that ES process would cause severe plastic deformation and improve the dynamic recrystallization of AZ31 magnesium alloy. The simulation results and calculated Zener-Hollomon parameters showed that the grains of magnesium would be refined gradually during ES process.
... Thermal conductivity (W/mK) [19] 25 °C (96.4), 100 °C (101), 200 °C (105), 300 °C (109), 400 °C (113), Heat capacity (N/mm 2 C) [20] 327 °C (2,09684), 527 °C (2,27484) Emissivity [20] 0.12 Hill model's coefficients [17] F , G , H , L , M , N 0.5, 0.5, 0.5, 1.5, 1.5, 1.70 where h=4,5 W/m 2 K [17] was assumed the heat transfer coefficient between work piece material and environment. T w and T 0 are the temperature of the work material and ambient temperature, respectively. ...
... Thermal conductivity (W/mK) [19] 25 °C (96.4), 100 °C (101), 200 °C (105), 300 °C (109), 400 °C (113), Heat capacity (N/mm 2 C) [20] 327 °C (2,09684), 527 °C (2,27484) Emissivity [20] 0.12 Hill model's coefficients [17] F , G , H , L , M , N 0.5, 0.5, 0.5, 1.5, 1.5, 1.70 where h=4,5 W/m 2 K [17] was assumed the heat transfer coefficient between work piece material and environment. T w and T 0 are the temperature of the work material and ambient temperature, respectively. ...
The aim of this study is to investigate the process of friction stir welding (FSW) by using finite element method (FEM). Currently, the materials that are difficult to be joined with conventional fusion methods can now be easily joined with the method of friction stir welding. In this paper, the welding capability of many different materials with this method has been investigated by using analytical and numeric methods. In this study, a finite element (FE) model was developed for welding process with friction stir welding of AZ31 magnesium alloy. This model was performed by the software of DEFORM 3D finite element in 960, 1,964, and 2,880 rpm rotational speeds and in 10 and 20 mm min−1 transverse speeds. The temperature values taken from experiments and the temperature values with FEM are compared, and according to these results, it can be stated that the FE model gives reasonable results with experimental results based on temperatures values. Hence, the FE model can be used to predict other parameters of FSW process in future studies.
The present study examines the influence of Ca or Nd on the microstructure and texture modification during indirect extrusion and after subsequent annealing of Mg-Zn based alloys. The addition of such elements influence the recrystallization processes, i.e. dynamic (DRX) and static recrystallization (SRX), and leads to distinctive texture changes of samples extruded at different extrusion speeds. In the binary Mg-Zn alloys, the resulting texture after extrusion is the classical basal type texture, where there is an alignment of basal planes along the arc between the <10-10> and <11-20> poles. This development is independent of the extrusion speed, as the resulting microstructures are almost completely recrystallized. In the case of the Mg-Zn-Ca, there is a distinctive <10-11> component together with a <11-20> pole, while in the Mg-Zn-Nd alloy the so-called <11-21> rare-earth texture component and the <20-23> pole intensity are observed as DRX dominates the microstructural development. It is found that this distinctive behavior can be changed if partially recrystallized microstructures are subsequently annealed. This leads to an increase of the importance of SRX and a different resulting texture while maintaining a similar grain structure. Both recrystallization processes lead to different mechanical properties, yielding behavior and toughness as a result of the different texture development.
A new severe plastic deformation called TES (tube extrusion shearing) process, which combines direct extrusion with two-step shearing, is developed to manufacture tubes made of wrought AZ31 magnesium alloy. To explore the deformation mechanisms of TES process, both experiment and numerical simulation are carried out. Three-dimensional finite element modeling is used to investigate the plastic deformation behaviors of wrought magnesium alloy during TES process. Experiments show that by use of TES process the microstructures can be refined to 50% of the original grain size and with more uniform grain distribution. TES process could improve hardness obviously by comparing which fabricated by direct extrusion. Numerical results indicate TES increases the cumulative strains effectively by direct extrusion and additional shearing.
A new severe plastic deformation method called extrusion-shearing shorten for “ES” has been developed to fabricate the ultra-fine grained AZ61 magnesium alloys. The correlation theories of ES process have been studied which includes cumulative strain and Zener-Hollomon parameter etc. Simulations of ES process for wrought AZ61 magnesium alloy have been performed using three-dimensional finite element method. ES dies with one step shearing and two step shearings have been designed, manufactured and installed onto thermo-mechanical simulator and industrial horizontal extruder, respectively. Microstructures evolution has been observed and analysed. The influences of the ES processes on the grain refinements of AZ61magniesium alloys during multistage processes have been investigated. Based on the experimental, simulation and theoretical results, ES process could increase the cumulative strains enormously and refine grain sizes by direct extrusion and additional shearings. ES process can produce the serve plastic deformation and improve the volume fraction of dynamic recrystallization. Continuous dynamic recrystallizaion is the main reason for grain refinements during ES process.
In order to research the dynamic recrystallization (DRX) and grain refinement mechanisms in the process of extrusion through the rotating container, hot compression experiment of AZ31 magnesium alloy was carried out. Through the combination of experimental data and Yada empirical model, the DRX model of AZ31 magnesium alloy was established. Based on this DRX model, the numerical simulation of AZ31 magnesium alloy extrusion through the rotating container process was performed. The research results indicated, with the same process parameters of conventional extrusion, the shear stress increased significantly at the same position during the process of extrusion through the rotating container. This stress change promoted the occurrence of DRX and the increased recrystallization volume fraction. The average grain size obviously decreased. The equiaxed grains increased and the distribution uniformity was improved. These characteristics provided a theoretical basis for a better understanding of the enhanced comprehensive mechanical properties during the extrusion through the rotating container.
Due to the problem that high energy consumption and low material utilization ratio in extrusion process for lower plastic alloy, this paper proposes a new forming technology, named extrusion with steadily rotating container, and a set of special container is designed. Compared to the extrusion with rotating die, which is only applicable to circular section products, the new forming technology can effectively avoid the axial "cutting" of vertical die orifice during special-shaped products extrusion forming. The results show that, compared with conventional extrusion, the plastic zone expands significantly in the extrusion with rotating container, and the peak of forming load decreases by 42.1%.
