The Twist Multi Channel Angular Pressing (TMCAP) process is presented for the first time to investigate the mechanical properties of AL1050 numerically and experimentally. TMCAP that can be ...categorized as a SPD method is a process based on combining the Equal Channel Angular Pressing and Twist Extrusion processes. The process was simulated entirely using dynamic explicit solution of ABAQUS/software. Based on the simulation results as well as considering the hydrostatic pressure effect on die filling and strain distribution, the TMCAP die was designed in which the horizontal channel creates a required hydrostatic pressure during the process. This process can effectively impose large strains to a bulk material to enhance the mechanical properties. Upon on a single pass of routes, a value of nearly 2.4 total strain was obtained without having significant changes in the billet cross section. In addition, the load obtained from simulation of TMCAP process at the first pass was about 22 tons which has a good conformity with the value obtained from experimental study. The process was also repeated up to four passes to evaluate the subsequent mechanical properties such as the flow stress and the Vickers micro-hardness as well as microstructure after each pass.
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In this research, conventional extrusion and twist extrusion are combined to propose a new design for single-pass severe plastic deformation technique, which is called Rectangular Vortex Extrusion ...(RVE). The effects of different parameters like RVE die twist angle as well as friction condition at the die-sample interface were studied using finite element analysis. It was shown that RVE can be successfully performed as a single-pass severe plastic-deformation technique to impose high strain values within the sample. It was revealed that the die geometry has the primary role in imposing torsion on the sample, while friction does not significantly increase the process potential for imposing additional torsion. Meanwhile, friction at the interfaces was found to be effective for increasing the intensity of the velocity gradient within the deformation zone. The results show that increasing the die twist angle and friction condition have a synergetic effect on increasing the accumulated strain values.
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Ultrafine-grained (UFG) materials have been of great attention due to their considerable behavior compared to coarse-grained counterparts. Also, the machinability of these UFG materials is of great ...importance because of the machining significance in manufacturing the final shape of industrial components. Hence, this study dealt with machinability in relation to the microstructure and mechanical properties of the UFG pure copper processed by the twist extrusion. The remarkable microstructure evolution through the dynamic recrystallization mechanisms improved the tensile strengths and hardness of the twist extrusion processed pure copper. Also, the reduction of ductility in the UFG copper compared to the initial state was related to the change of tensile fractography mechanism in which the large and deep dimples transformed into the combined small and shallow dimples with some cleavage planes in the UFG copper. Furthermore, the enhanced machinability of the processed sample was related to its lower thermal conductivity and the development of strain localization within the narrow shear bands which lead to the production of discontinuous short chips. Hence, the formation of the UFG structure is a suitable option to attain the enhanced machinability behavior of copper as one of the most used metals.
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In the current study, aluminium 6063 alloy (AA6063) was successfully gain refined by twist extrusion (TE) technique. TE is a representative severe plastic deformation process to fabricate ...ultrafine-grained in bulk materials by repetitive passes. In order to investigate the influence of back pressure, a direct extrusion (DE) channel was embedded after the twist zone and the behavior of AA6063 was investigated and compared with and without this channel. Analyzing microstructural evolutions by scanning electron microscope and Vickers microhardness evaluations showed that, adding the DE channel increased the hardness distribution and a more homogenous structure was obtained. Finite element analysis was utilized to study the distribution of the equivalent plastic strain (PEEQ) numerically. According to the obtained results, with applying the TE process, strain increase was observed all over the sample surface, whereas modeling the DE channel after the twist zone caused a better homogeneity in the PEEQ distribution of the transverse cross-section. The PEEQ distribution during TE process can be correlated to the extent of grain refinement and the uniformity of ultrafine grains. This method seems to be very interesting and very promising for the future industrial application.
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Hot extruded (EX) AZ61 magnesium alloy was processed by the twist channel angular pressing (TCAP) method, which combines equal channel angular pressing (ECAP) and twist extrusion (TE) processes and ...significantly improves the efficiency of the grain refinement process. Both the initial hot extruded AZ61 alloy and the alloy after completion of TCAP processing were examined by using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) and their corresponding micro-tensile testing (M-TT) and hardness testing at room temperature. The results showed that the microstructure of hot extruded alloy was refined well by TCAP due to dynamic recrystallization (DRX) caused by TCAP. The tensile properties, investigated by micro-tensile testing (M-TT), of the AZ61 alloy were significantly improved due to refined microstructure. The highest tensile properties including YS of 240.8 MPa, UTS of 343.6 MPa and elongation of 21.4% of the fine-grained alloy with average grain size below 1.5 µm was obtained after the third TCAP pass at 200 °C using the processing route Bc.
Twist Extrusion is kind of severe plastic deformation process which enhances the strength of materials by applying a shear plastic strain and consequently grain refinement. The strain distribution is ...minimum at the center of the die and is maximum at outer surfaces. In this article, the plastic strain distribution will be studied within a hollow section. The billet is solid in previous experimental and numerical studies in the literature, but by adding a new die (mandrel) for extruding the hollow billet, it is possible to twist extrude hollow sections. A finite element model is developed in the ABAQUS finite element software and the effects of process parameters (slope line angle, thickness and friction coefficient) on equivalent plastic strain distribution are investigated. The numerical results show that the equivalent plastic strain will be increased by increasing the slope line angle and decreasing the thickness and more homogeneity in the strain field will be obtained. In addition, increasing the friction coefficient higher than 0.2 can lead to an increase in induced plastic strain. The required force for twist extrusion will be increased by increasing the friction coefficient.
Graphical Abstract
•MA and PM routes were applied to fabricate a new composite.•Composites have binary matrix of Al–4Cu and reinforcement of 2wt% TiO2 nano-particles.•Composites were deformed severely through twist ...extrusion for 1, 2 and 4 passes.•With increasing the number of passes a homogeneous distribution particles occurred.•An ultrafine-grained nano-structure was obtained.
Mechanical properties of new composites having a binary matrix of Al–4Cu reinforced with TiO2 nano particles were investigated. The composites which consisted of 2wt% and 8wt% of TiO2 reinforcement particles, were fabricated using mechanical alloying and a powder metallurgy route. Morphology, phases and compounds formed during ball milling and densification of samples were studied. With increasing percentages of the reinforcement particles, mechanical properties of the composites were enhanced. Microstructural evolution and mechanical properties changes of the composites after application of twist extrusion (TE), as a severe plastic deformation (SPD) process, were also investigated. It was revealed that the more TE passes the higher hardness and yield strength obtained. In addition, increasing TE passes, led to occurrence of a more homogeneous distribution of the reinforcement particles within the structure, and development of an ultrafine-grained nano-structure. The maximum allowable number of TE passes was found to be four, above which the materials failed.
Twist extrusion process which is based on the extrusion of a prism work piece through a die with a twist channel, is one of the severe plastic deformation (SPD) methods. In this investigation, the ...twist extrusion process under high pressure is simulated using the finite element method. The ABAQUS code is used for the FEM. The Johnson–Cook constitutive equation is used to describe the behavior of the Ti–6Al–4V alloy during the twist deformation. Since the deformations of Ti–6Al–4V alloy are performed at high temperature, therefore the effects of the temperature and strain rates under high pressure on the flow behavior are discussed. Furthermore, the magnitude of accumulative strain distributions which determines the sizes of final ultra fine grain (UFG) across the cross-section is presented. In this study, the modes of deformation during the twist extrusion process are also considered. It is found that both the pure shear and simple shear modes are present in the twist extrusion process across the sample. This procedure could be extended to other materials behavior, as well.
The severe plastic deformation (SPD) processes used for applying an extensive shear plastic strain in the material and consequently grain refinement and increase in the strength of materials. The ...strain distribution is very important and more homogenous plastic strain is desired in SPD process modifications. In this article, four different die configurations will be investigated during the hollow twist extrusion (HTE) process and the plastic strain distribution will be compared within a hollow section. The die configurations are similar slope line angle of inner and outer dies (SD), opposite slope line angle between the inner and outer dies (OD), outer die with twist zone and flat inner die (FI) and inner die with twist zone and flat outer die (FO). The Von-Mises stress, plastic strain, and material deformation are studied by using a finite element model which was developed in the ABAQUS finite element software. The results show that the FI and FO die configuration produce higher plastic strains than SD die configuration, but the strain homogeneity is not satisfactory. The plastic strain is higher and more homogenous for OD die configuration in comparison to the other die configurations. The required force for twist extrusion of the billet is almost equal for FI and FO die configuration (~ 216 kN) and increases to about 256 kN for SD die configuration (16% increase). The required force for OD die configuration increased once more to 370 kN (44.5% increase). The element distortion along the two defined paths determined the material flow during the HTE process. The flat die retards the material flow for FI and FO die configurations. A significantly material flow will happen for OD die configuration. The element distortion leads to better material mixing in OD die configuration and consequently higher magnitude and more homogenous plastic strain distribution and higher grain refinement will be obtained.
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