Asymmetric Extrusion Research Articles

A novel strategy to achieve uniform ultrafine grains in Mg-Al-Sn-Ca alloy via pre-twinning combined with differential-thermal asymmetric extrusion

Obtaining fine grains with weak textures is an efficacious way of simultaneously improving the strength and ductility of magnesium (Mg) alloys. In this paper, an Mg-Al-Sn-Ca alloy with uniformly ultrafine grains and a weak texture has been prepared via pre-twinning followed by differential-thermal asymmetric extrusion (DAE). The alloy exhibits good strength and ductility (ultimate tensile strength: ∼381 MPa; elongation: ∼22 %). The results show that {102} tensile twins significantly promote dynamic recrystallization (DRX) during DAE, which beneficial for the formation of uniform fine grain structure and weak bimodal texture. This research provides valuable insights and methods for tailoring excellent mechanical properties of Mg alloys, facilitating their practical application in various engineering scenarios.

Enhanced Strength–Ductility Synergy of Mg-Al-Sn-Ca Alloy via Composite Asymmetric Extrusion

Fine-grain and weak-texture magnesium alloys are the long-term development targets of lightweight structural materials. In this study, a new composite asymmetric extrusion (CAE) is developed, which, coupling with an asymmetric die and an asymmetric billet, is proposed to improve the strength–ductility of the Mg-3.8Al-1.1Sn-0.4Ca alloy. The influence of the asymmetric billet on the microstructure and mechanical properties was investigated. The findings revealed that the asymmetric billet can induce greater plastic deformation, resulting in an increase in the cumulative strain and an improved nucleation rate. The CAE sheets exhibit fine grains (4.4 μm) and a weak tilted texture (7.57 mrd). Furthermore, the asymmetric billet results in the microstructure not forming a gradient microstructure under gradient strain along the transverse direction (TD) direction. The CAE sheets exhibited good mechanical properties, with a yield strength (YS) of 253 MPa, ultimate tensile strength (UTS) of 331 MPa, and elongation (EL) of 20%. This development shows promise in achieving high-efficiency, low-cost production of magnesium alloys.

Microstructural regulation and mechanical behavior of asymmetrically extruded high-content TC4p reinforced AZ31 composite

Asymmetric extrusion (AE) is frequently used to weaken the texture of magnesium (Mg) alloys to improve their mechanical properties. In this paper, to explore the influence of asymmetric extrusion on the microstructure and mechanical properties of Mg matrix composites (MMCs), we synthesized TC4/AZ31 composite sheets via ball milling coupled with sintering and then various extrusions (including conventional extrusion (CE), transverse-directional AE (TDE), and normal-directional AE (NDE)). The differences in microstructure and performance among the three processed samples were compared and analyzed using SEM, XRD, EBSD characterization and tensile testing. The results showed that the asymmetrically extruded samples achieved better mechanical properties compared to their CE counterparts. It found that the grain refinement was relatively significant and texture evolution was dispersed in AE samples compared to the CE ones, which was attributed to the TC4 particle (TC4p) disturbance and extra asymmetric shear of matrix flow. Three different macro-textures were obtained in various extruded processes, and the micro-texture of each sample changed in diverse regions. Based on grain orientation spread (GOS) analysis, the introduction of TC4p resulted in dynamic recrystallization (DRX) and particle-stimulated nucleation (PSN) effects during the AE process at 350 °C. The mechanisms of the combination of ductility and strength in the AE-processed sheets were related to the finer grains, high Schmid factor (SF), evenly distributed dislocations and scattered texture. This work can also provide the feasibility and prospects of applying asymmetric extrusion to MMCs.

Asymmetric Extrusion Technology of Mg Alloy: A Review.

Magnesium (Mg) alloy is a widely used lightweight metal structural material due to its high specific strength and stiffness, excellent damping performance, and recyclability. Wrought Mg alloys are particularly favored in fields such as aerospace, transportation, and biomedical stents. However, most wrought Mg alloys with a hexagonal close-packed (HCP) crystal structure lack sufficient independent slip systems to meet the von Mises criterion for uniform plastic deformation at room temperature. This can result in the formation of a strong basal texture during plastic deformation and poor room temperature plastic formability. Enhancing the room temperature forming performance is therefore a crucial challenge that needs to be addressed in order to expand the application of Mg alloy sheets. Our research group has comprehensively summarized significant work and the latest research progress in improving the room temperature forming of Mg alloy sheets via extrusion technology in recent years. Specifically, we have developed a new type of asymmetric extrusion technology that combines material structure evolution, mechanical properties, and forming behavior analysis. We have elucidated the extrusion process characteristics, texture control mechanism, and forming properties of Mg alloy sheets through plastic deformation mechanisms, mold design, and finite element numerical simulation. The findings of our study present an innovative extrusion technology for the fabrication of highly formable Mg alloy sheets, which can be utilized in various applications.

METHOD FOR CALCULATING TECHNOLOGICAL PARAMETERS FOR CONSTRAINED EXTRUSION OF RECTANGULAR BRACKETS. Part 2

The continuation of the methodology for calculating the technological parameters of the process of constrained extrusion of rectangular brackets under conditions of plane deformation in the general case of misalignment of the punch and die is outlined. The calculation of limiting cases of asymmetric extrusion, which, on the one hand, is reduced to a symmetrical extrusion, and, on the other hand, to a complete overlap of a small outflow gap, is considered. The above formulas make it possible to determine such important parameters of the stamping process as the total and specific deforming forces, as well as the heights of the walls formed as a result of extrusion.

METHOD FOR CALCULATING TECHNOLOGICAL PARAMETERS FOR CONSTRAINED EXTRUSION OF RECTANGULAR BRACKETS. Part 1

The beginning of the methodology for calculating the technological parameters of the process of constrained extrusion of rectangular brackets under conditions of plane deformation in the general case of misalignment of the punch and matrix is outlined. Described the definition of sections of the working stroke, which were free extrusion, partially constrained extrusion and completely constrained extrusion. The calculation of limiting cases of asymmetric extrusion, which, on the one hand, is reduced to a symmetrical extrusion, and, on the other hand, to a complete overlap of a small outflow gap, is considered. In the developed technique, extrusion of both non-hardening and hardening material is considered. In the latter case, the consideration of the hardening of the extruded material is described in detail. The above formulas make it possible to determine such important parameters of the stamping process as the total and specific deforming forces, as well as the heights of the walls formed as a result of extrusion.

Influence of different extrusion methods on the microstructure, texture evolution and mechanical property of Tip/AZ31 composite

Asymmetric extrusion (AE) deformation has been proved to be an effective way to weak the basal texture of Magnesium (Mg) alloys, improving their mechanical properties. However, the influence of AE process on particle reinforced Mg-matrix composites (MMCs) remains unclear. Thus, in this paper, the effect of different deformation modes (conventional extrusion (CE) and AE) on the microstructure, texture and mechanical properties of 6 wt% Tip/AZ31 composite were comparatively investigated. The results showed that the two extrusion methods induced disparate particle deformation zones (PDZs) effects, which mainly related to the deformation accumulation and the distribution of Ti particle (Tip). The microstructure characterization and finite element analysis (FEA) indicated that the Tip distribution was uneven in the AE process compared with the CE process. In addition, the grain orientation of CE- and AE-processed samples showed a pronounced difference. The discrepancy in texture components was mainly related to the difference in the stress states of matrix and Ti particle status. The current research provides insights into the development of Ti particle reinforced Mg-based composites with great properties and structures.

Microstructure and mechanical properties of AZ31 alloy prepared by cyclic expansion extrusion with asymmetrical extrusion cavity

The microstructure, texture evolution and mechanical properties of AZ31 magnesium alloy were investigated during the cyclic expansion extrusion with the asymmetrical extrusion cavity (CEE-AEC) process. The results show that continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) occur during the CEE-AEC process. After 3 passes, the microstructures of the deformed samples are refined, and the average grain size of the alloys in asymmetrical cavity region is 6.9 μm. The maximum intensities of the basal textures increase with the increase in the number of passes, and the basal textures are deflected during the deformation process. The basal texture of the alloys in asymmetrical cavity region is tilted by approximately ±45° from the normal direction (ND) to the extrusion direction (ED). Grain refinement strengthening and texture deflection significantly improve the comprehensive mechanical properties of the deformed alloys. After 3 passes, tensile yield strength (TYS), ultimate tensile strength (UTS) and elongation-to-failure of the alloy in the asymmetric cavity region are 146 MPa, 230 MPa and 29.7%, respectively.

Microstructure and mechanical properties of pure magnesium prepared by CEE-AEC at different temperatures

Cyclic expansion extrusion with an asymmetrical extrusion cavity (CEE-AEC) was carried out on pure magnesium up to 3 passes at different deformation temperatures of 250 °C and 350 °C. The microstructure and texture evolution of its edge and center regions are studied respectively, and their mechanical properties are correlated. The results show that there is an incomplete dynamic recrystallization (DRX) region in pure magnesium deformed at 250 °C. Therefore, pure magnesium processing at 250 °C has a larger grain size and higher texture strength than that processing at 350 °C. According to the tensile test, the ultimate tensile strength (UTS) of different positions of different temperatures is very close because the DRXed grains grow at 350 °C. But the value of tensile yield strength (TYS) is nearly doubled, the main reasons are that the effect of (0001) basal slip and texture softening is greater than that of grain refinement.

Reinforcing effects of cyclic expansion extrusion with an asymmetrical extrusion cavity (CEE-AEC) on pure magnesium

In this paper, a relatively novel severe plastic deformation method cyclic expansion extrusionwith an asymmetrical extrusioncavity (CEE-AEC) was carried out to prepare large-sized pure magnesium (Mg) with high comprehensive performance. Finite element analysis (FEM) was used to study the plastic deformation process and Electron Back-Scattered Diffraction (EBSD) was aimed to research the microstructural evolution. Three passes and isothermal deformation at 250 °C were chosen to satisfy the research. The central part of the billet was cut as the research area, and the resultant microstructure and mechanical properties were analyzed systematically. The results showed that the grain size was remarkably refined due to continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX). Twins participated in the progress of deformation. The shear strain introduced by the asymmetrical extrusion cavity determined the formation of inclined basal texture, leading to the increasing value of basal 〈a〉 slip system Schmid factor. The best comprehensive tensile properties were obtained after three passes of deformation, and the contributions came from grain refinement strengthening and texture modification, respectively.

The improvement of grain refinement, texture modification and mechanical properties of pure Mg prepared by cyclic expansion extrusion with an asymmetric extrusion cavity

In this article, a new type of severe plastic deformation process named cyclic expansion extrusion with an asymmetric extrusion cavity (CEE-AEC), was used to prepare pure magnesium with three passes repetitive deformation at 250 °C. This article mainly studies the microstructure evolution, texture analysis and mechanical properties of pure magnesium. The results display that the grain size is refined, from 74 um to 19 um, which is attributed to continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX). With the increasing CEE-AEC passes, the texture is weakened, and the (0001) plane of a large number of grins are inclined from the ED direction. The Schmid factor that activates the basal slip system gradually increases from 0.29 to 0.3 after three passes. After three passes of CEE-AEC, from the tensile tests of the deformed samples at room temperature, it can be seen the samples have excellent comprehensive mechanical properties, the tensile yield strength (TYS) is 54 MPa, ultimate tensile strength (UTS) is 110 MPa, and fracture elongation is 19%.

Microstructure evolution, texture and mechanical properties of a Mg–Gd–Y–Zn–Zr alloy fabricated by cyclic expansion extrusion with an asymmetrical extrusion cavity: The influence of passes and processing route

In the present work, two processing routes (A and B) with 3 CEE-AEC passes are performed on Mg–13Gd–4Y–2Zn–0.4Zr alloys, and the resultant microstructure evolution, texture analysis and mechanical properties are investigated systematically. The core difference between the two processing routes is the orientation between the expansion and extrusion steps, i.e., they are parallel to each other for on route A and perpendicular to each other for route B. The results show that a remarkable grain refinement is achieved via both processing routes due to dynamic recrystallization (DRX). Fine equiaxed grains are observed in the samples processed with route B with a final size of 3.6 ± 0.4 µm compared to the grain size of 4.5 ± 0.5 µm with route A. With an increasing number of CEE-AEC passes, the overall texture intensity decreases, and the basal texture gradually changes to the mixed texture components. The shear deformation introduced by the asymmetrical extrusion cavity promotes a broad angular distribution of the basal planes on routes A and B, leading to an obvious increase in the Schmid factor for the activation of the basal 〈a〉 slip system. The tensile test at ambient temperature reveals that the comprehensive mechanical properties are improved, and the conventional mechanical anisotropy of as-received alloys is alleviated by successive CEE-AEC processing, which is mainly derived from the competitive balance relation between the grain refinement and texture modification.

Macroscopic Model of Two-Phase Compressible Flow in Double Porosity Media

A macroscopic model of two-phase flow of compressible liquids in a compressible double porosity medium is developed and used to analyse various qualitative mechanisms of the occurrence of memory (delay). The two main mechanisms are non-instantaneous capillary redistribution of liquids, and non-instantaneous relaxation of pressure. In addition, cross effects of memory arise, caused by asymmetric extrusion of liquids from pores due to phase expansion and pore compaction, as well as nonlinear overlap of compressibility and capillarity (non-linear extrusion). To construct the model, the asymptotic method of two-scale averaging in the variational formulation is applied. Complete averaging has been achieved due to the separation of nonlocality and nonlinearity at different levels of the asymptotic expansion. All delay times are explicitly defined as functions of saturation and pressure.

Microstructure and Texture Evolution of AZ31 Alloy Prepared by Cyclic Expansion Extrusion with Asymmetrical Extrusion Cavity at Different Temperatures.

This work is to study the microstructure and texture evolution of AZ31 alloy prepared by cyclic expansion extrusion with an asymmetrical extrusion cavity (CEE-AEC) at different deformation temperatures. The result shows AZ31 alloy undergoes continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) during CEE-AEC processing. At the initial stage of deformation, AZ31 alloys exhibit similar bimodal microstructure of coarse deformed grains surrounded by fine DRXed grains. As the passes increase, the cumulative strain increases, and the coarse grains of all samples are almost replaced by fine equiaxed grains. The average grain sizes and the basal texture intensities of the deformed samples increase as the deformation temperature increases. In addition, due to the existence of an asymmetrical cavity, as the passes increase, the basal textures of all samples are deflected with maximum intensities increase, and even an unusual bimodal texture is formed, resulting in a soft orientation that is easy to basal slip.

High Ductility with a Homogeneous Microstructure of a Mg–Al–Zn Alloy Prepared by Cyclic Expansion Extrusion with an Asymmetrical Extrusion Cavity

In the current work, cyclic expansion extrusion with an asymmetrical extrusion cavity (CEE-AEC), as a relatively novel severe plastic deformation method, was applied to fabricate an AZ31B magnesium alloy plate with a size of 50 × 100 × 220 mm, and the resultant microstructure, texture development, and mechanical properties were systematically investigated. A refined and homogeneous grain structure was achieved after three passes of deformation due to dynamic recrystallization. The grain refinement degree in comparison to as-cast alloys was more than ~96%. With the increasing number of CEE-AEC passes, a basal inclination texture was gradually formed, with the basal planes inclined ~45° from the transverse direction to the extrusion direction, which could be attributed to the introduction of an asymmetrical extrusion cavity that led to an increasing Schmid factor for the activation of basal <a> slip systems. The comprehensive mechanical properties were improved by successive multi-passes of CEE-AEC processing, especially due to the ductility reaching to 30.0 ± 1.3% after three passes of deformation. The competition between the grain refinement and texture modification were the main strengthening mechanisms.

Vpliv postopka ciklične ekspanzijske ekstruzije z asimetrično ekstruzijsko votlino na mikrostrukturo in razvoj teksture Mg-13Gd-4Y-2Zn-0,5Zr zlitine

Vpliv postopka ciklične ekspanzijske ekstruzije z asimetrično ekstruzijsko votlino na mikrostrukturo in razvoj teksture Mg-13Gd-4Y-2Zn-0,5Zr zlitine

Design and Implementation of Asymmetric Extrusion Die Using Bezier Technique

Extrusion is a process that used to create objects of a fixed cross-sectional profile. A material is pushed through a die of the desired cross-section. The main advantage of this process with respect to other manufacturing processes is its ability to create very complex cross-sections, while the limitation of extrusion process is used to produced just a symmetric profile so this paper proposed an adopted algorithm that used to design and implementation the Asymmetric extrusion die that used to prevent the twisting that caused in metal when used to produce the Asymmetric product, and in other wise reduce the total extrusion power and die pressure distribution on metal during extrusion process. This adopted design was implemented in this work using Teflon material in both symmetric and asymmetric profile using CNC milling machine to demonstration the success of this algorithm.

A novel severe plastic deformation method and its effect on microstructure, texture and mechanical properties of Mg-Gd-Y-Zn-Zr alloy

In this paper, cyclic expansion extrusion with an asymmetrical extrusion cavity (CEE-AEC) was proposed as a novel severe plastic deformation process for fabricating bulk ultrafine-grained (UFG) metals. Increasing the size of the processed sample and introducing the shear strain by attaching an asymmetrical extrusion cavity are the core advantages of this technology. The CEE-AEC process was applied to Mg-13Gd-4Y–2Zn-0.4Zr alloys for four passes deformation with the decreasing temperature, and then the microstructure evolution, texture analysis, and mechanical properties were investigated. Microstructure results show that a dramatical grain refinement is achieved from initial value of 24 ± 0.3 μm to 1.4 ± 0.3 μm which is mainly led by continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) as well as the particle-stimulated nucleation (PSN) induced by interdendritic long-period stacking ordered (LPSO) phases. With increasing CEE-AEC passes, the intensities of basal texture are gradually weakened, and the basal plane tends to incline to transverse and normal directions with different degrees of different passes, leading to a remarkable increase in Schmid factor for the activation of basal slip system. Tensile tests at room temperature (RT) indicate that the samples after three-passes of CEE-AEC exhibit the best comprehensive mechanical properties with tensile yield strength (TYS) of 302 MPa, ultimate tensile strength (UTS) of 330 MPa, and fracture elongation of 6.1%, which are mainly ascribed to the grain refinement, broken of interdendritic block-shaped LPSO phases, and texture modification.

Effects of deformation processes on morphology, microstructure and corrosion resistance of LDHs films on magnesium alloy AZ31

Highly oriented Mg-Al layered double hydroxide (LDHs) films were deposited on magnesium alloy AZ31 with different deformation processes by an easy in-situ growth method. The characteristics of the films were investigated by optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical, immersion and hydrogen evolution tests. The corrosion protection performance ranked the LDHs films as the increasing series: CS-LDHs (as-cast sample with LDHs) < AE-LDHs (asymmetric extrusion sample with LDHs) < SE-LDHs (symmetric extrusion sample with LDHs) < RS-LDHs (rolled sample with LDHs). A thicker and more compact LDH conversion coating was formed on the RS sample, and had the best corrosion protection performance.

Microstructure and mechanical properties of Mg-Gd-Y-Zn-Zr alloy by cyclic expansion-extrusion with an asymmetrical extrusion cavity (CEE-AEC)

The effect of cyclic expansion-extrusion with an asymmetrical extrusion cavity (CEE-AEC) passes on microstructure and mechanical properties of Mg-13Gd-4Y-2Zn-0.5Zr (wt%) alloy were investigated in this research. The alloy was subjected to 1, 2 and 3 passes at 480 °C, 460 °C and 440 °C, respectively. Optical microscope (OM), scanning electron microscope (SEM) and electron back-scattered diffraction (EBSD) was used to study microstructure evolution with different passes. The fraction of coarse grains decline and fine dynamic recrystallization (DRX) grains increase with the CEE-AEC process pass increase. The average grain size is refined from 20 μm to 13.6 μm after 2 passes CEE-AEC. In addition, the average grain size drops rapidly to 1.8 μm after 3 passes. The as-received alloy and CEE-AEC processed alloys were subjected to the tensile test at room temperature (RT). The superior mechanical properties at RT with tensile yield strength (TYS) of 348 MPa after 1 pass and fracture elongation of 8.1% can be obtained after 3 passes.