Extrusion Strain Research Articles

Design and analysis of extrusion die for T-shaped sheet materials

Abstract The study explores plastic deformation behavior of T-shaped plates using DEFORM™ 3D, a perfect plastic finite element analysis software that considers T-shaped and double T-shaped extrusion dies as rigid bodies and compares effective strain, effective stress, blank temperature, die wear and temperature conditions. Moreover, the study employed the machine learning step descent method to predict effective stress and effective strain. Furthermore, the Pearson product difference correlation was utilized to examine the relationship between effective stress, effective strain, and temperature in T-shaped extrusion. Lastly, META analysis was conducted to synthesize statistical data on effective stress and temperature from various research.

A method for predicting the yield strength of AZ31 magnesium alloy bars processed by ambient extrusion

Magnesium alloys have strong mechanical properties anisotropy due to their universal basal texture. This study develops a novel method for predicting the yield strength of AZ31 extruded bars with basal fiber texture. From series tensile and compressive tests on ambient extruded bars with different loading direction, the relationship between yield strength, loading direction and extrusion strain was summarized. With varying loading direction, tensile and compressive yield strength can be fitted by linear and nonlinear equations in a strength coordinate system where yield strength can be calculated on different loading direction. Furthermore, parameters of yield strength equations can also be fitted by different equations. Then, from the parameter equations to yield strength equations, tensile and compressive yield strength can be predicted on different loading direction for extruded bars with different extrusion strain.

Effects of extrusion die cavity on the texture components and the associated mechanical properties for ZK60 magnesium alloy

This work managed the extrusion strain path by designing various extrusion die cavities, successfully realizing the texture modification for the ZK60 magnesium alloy. The mechanisms involving the texture dependence on the extrusion die cavity as well as their effects on the mechanical properties were emphatically investigated. Results showed that dynamic recrystallization refined the grain size and improved the microstructure homogeneity in the three extrusion specimens, but did not produce too large microstructure differences. By comparison, significant texture differences developed owing to the various extrusion die cavities, which here were mainly reflected in the strong or weak texture components for the c-axes//TD and the c-axes//ND. Such texture differences started from the deformation texture instead of the recrystallization texture whose roles only consisted in dispersing the texture component and reducing the texture intensity. The results from the finite element analysis and the visco-plastic self-consistent model indicated that, in order to accommodate the different strain components induced by the extrusion die cavities, slip systems or tension twinning were activated differently, and this was the critical reason causing the above texture differences. One modified Hall-Petch relationship was adopted to analyze the conjoint effects of grain refinement and texture variation on the yield stress. Additionally, the quantitative results about deformation mechanism activation fractions demonstrated that the texture variations influenced the competition relationships between the twinning induced deformation and the slip dominant deformation, and the former generally produced the lower yield stress and the increasing stage of strain hardening rate, while the latter produced the higher yield stress and the continuous decline of strain hardening rate.

Effect of long-period stacking ordered phase on dynamic recrystallization in Mg-Y-Zn-Zr alloy processed by backward extrusion

During the backward extrusion process, the impact of the long-period stacking ordered (LPSO) phase on dynamic recrystallization (DRX) in the Mg-10Y-2Zn-0.5Zr alloy was studied. The results show that DRX at the α-Mg/18R-LPSO interface belongs to the discontinuous dynamic recrystallization (DDRX) mechanism, and the DRX at the α-Mg/14H-LPSO interface belongs to the continuous dynamic recrystallization (CDRX) mechanism. Under the action of strain force, the 18R-LPSO interface migrates locally to form a “convex” structure. It was easy to produce high-density dislocations around the structure, which promoted DDRX at the α-Mg/18R-LPSO interface. The lamellar 14H-LPSO would undergo severe kink and form a large number of kink bands, providing favorable nucleation sites for CDRX grains. With the increase of the extrusion strain force, the lamellar 14H-LPSO kink angle gradually increases, which promotes the nucleation of CDRX grains at the kink band boundary. In addition, the production of 14H-LPSO kink activates prismatic <a>slip, pyramidal <a>slip and pyramidal <c+a>slip in the α-Mg matrix.

Texture weakening effect from [formula omitted] twins induced static recrystallization in ambient extrusion AZ31 magnesium alloy

In magnesium alloys, {101̅1} twins have great effect on their recrystallization behavior due to the high strain concentration in twinning zones. In this study, isothermal annealing was conducted on ambient extrusion AZ31 magnesium bars to investigate {101̅1} twins related static recrystallization and texture weakening effect. The results show that, during annealing, static recrystallization occurs firstly in {101̅1} twinning zones. After 300 ℃ annealing, equiaxed grains are obtained in these extrusion bars. With the increasing extrusion strain, the grain size decreases gradually and the basal texture becomes weaker. Tensile and compressive yield strength show a significant decrease after annealing, meanwhile, they follow a Hall-Petch relationship. However, a negative Hall-Petch coefficient K is found in tensile tests where the tensile yield strength decreases gradually with the reduced grain size. Different contribution from grain refinement and texture weakening on yield strength are discussed and separated. The texture weakening effect from {101̅1} twins induced static recrystallization is responsible for the negative Hall-Petch coefficient K during tensile tests.

Controlling Damage Evolution in Geometrically Identical Cold Forged Parts by Counterpressure

Abstract It is investigated to what extent the evolution of ductile damage in cold forging can be controlled without changing the geometry of the produced part. Besides the effects of strain hardening and residual stresses, damage, which is the nucleation, growth and coalescence of voids on microscopic level, affects product properties of the manufactured components such as fatigue strength, impact strength, or elastic stiffness. Former investigations have shown that the load path-dependent damage evolution in forward rod extrusion, and thus, the performance of produced parts can be controlled by the process parameters extrusion strain and shoulder opening angle. As these parameters also affect the geometry of extruded parts, design requirements of components might be violated by varying these. Thus, counterpressure is used to superpose purely hydrostatic stresses to forward rod extrusion in order to decrease triaxiality in the forming zone without causing geometric variations in the produced parts. The counterpressure is either introduced by a counterpunch or by modified process routes. The achieved improvements in product performance are in agreement with results obtained by variation of extrusion strain and shoulder opening angle as described in the literature. In addition, it is observed in tensile tests that damage in cold extruded parts does not significantly affect flow stress. All advancements in product performance are realized without affecting the products’ geometries.

Determination of Force and Pressure Functions for Backward Cold Extrusion of Aluminum Alloy 1350

A key indicator for the design of cold extrusion technology and materials is the force and pressure required to perform the process under different production conditions. Hence, this work is concerned with finding force and pressure functions of Aluminum 1350 for backward cold extrusion using regression method of experimental data. In order to find force and pressure functions considered, different mathematical formulas are used to obtain the optimum relations where several variables such as cavity diameter, semi-finished sizes, and extrusion strain are taken into account. Lack of data necessary for the calculation of the functions considered, depending on the different technological and construction parameters such as extrusion process, processed material, degree of deformation, form and dimensions of the part, semi-finished product and active elements of the molds requires the continuation of studies and research in this field. Analytical formulas, obtained using regression method, are considered essential for design and optimization purposes concerning backward extrusion for Aluminum 1350. Three different mathematical formulas have been developed for both pressure and force where good agreement has been found when compared to experimental records. Furthermore, cavity diameter and extrusion strain are found to be influential factors that affect the coefficients of force and pressure functions of cold backward extrusion.

Ambient extrusion induced working hardening and their effect on mechanical properties in AZ31 hot-extrusion bar

Varying degrees of strain was imposed to AZ31 hot-extrusion bars by ambient extrusion. Mechanical properties were tested along different loading direction to reveal the effect of working hardening on deformation mechanisms and strain hardening behavior. The results showed that, with the increase of extrusion strain, yield strength increased gradually with a sacrifice in ductility. The working hardening from ambient extrusion, on the other hand, showed varying effects for different loading direction due to respective dominating deformation mechanism. Due to the complex crystal orientation, an evident elastic-plastic transition (EPT) stage was found in the 0° and 45° samples. Working hardening could enlarge the EPT stage since it had different effect on basal slip, {101‾2} twinning and prismatic slip.

Active tectonic deformation around the Tarim Basin inferred from dense GPS measurements

The surrounding area of the Tarim Basin is featured by active tectonic deformation and intense seismic activity. The study of the crustal deformation characteristics of this area will help revealing the role of the Tarim Basin in the crustal evolution. In order to accurately obtain the deformation characteristics of this area, we firstly obtained the highly detailed and accurate three-dimensional (3D) crustal deformation velocities of the Tarim Basin and its surrounding areas through high-precision processing of existing Global Positioning System (GPS) data. Thereafter, the slip rate and strain rate fields of the main faults in the region were calculated based on the updated velocity results. The strain rate of the Altyn Tagh fault is dominated by shear strain and the strike slip rate is 8–10 mm/yr. The strain rate between the Tien Shan and Tarim Basin is dominated by extrusion strain, and the extrusion rate is 4–6 mm/yr. In addition to the large shear strain, there is also a certain tensile strain in the Tibetan Plateau. Geodetic results show that the main driving force for the deformation of the Tien Shan is the northward thrust of the Tarim Basin. The relative movement mode between the Tarim Basin and Tibetan Plateau mainly comprises the strike slip movement along the strike direction of the Altyn Tagh fault, with a small extrusion deformation. Therefore, the Tarim Basin has little influence on the north–south shortening deformation of the Tibetan Plateau.

Improving the plastic homogeneity of a magnesium alloy by introducing high volume fraction of twins during ambient extrusion

Abstract Ambient extrusion was conducted to impart different strains on an AZ31 magnesium alloy. Lamellar twins were observed in the strained samples, and twin density increased with strain. Uniaxial tensile tests were conducted on the extruded samples with different strains. An abnormal raise in elongation was observed at higher strains with high volume fraction of 10 1 ¯ 1 twins. With the increase of extrusion strain, the elongation decreased initially and then got increased from a critical strain e c r without any sacrifice in strength. The basal texture was weakened due to twinning related crystal lattice rotation. Basal slip was thus easier to activate inside the twinned region to accommodate the plastic strain leading to an increase in elongation. The special twinning skeleton structure was expected to sustain a high stress to resist the necking.

Numerical analysis and experimental validation of conjunction gear via hot forging-upsetting finishing-radial extrusion

The formation of hot forging-upsetting finishing-radial extrusion (HF-UF-RE) compound into conjunction gears is an innovative process. This study describes the most existing manufacturing methods of the conjunction gear. Simulation and experimental research is conducted using this new method. First, a type of extrusion die is designed to form the back taper. The finite element models of hot forging, finishing, and radial extrusion are then established to estimate the feasibility of formation process of this compound. This study analyzes the law of metal flow in the process, the influence of the finishing parameters on the surface quality, and the distribution of stress and strain in extrusion. Metal flows from the tooth tip to the tooth bottom during the finishing process. The finishing qualities of different finishing parameters have been discussed. Local plastic deformation occurs at the tooth bottom during radial extrusion. The gears formed by each process are consistent with the designed shapes and meet the application requirements of the conjunction gear. HF-UF-RE is feasible for the formation process of conjunction gears.

Plastic Flow Analysis in Hot Aluminum Extrusion of Asymmetric Parts

In this study, a design guideline for the die cavity and die bearing length distribution is proposed during an extrusion process of an asymmetrical thin sheet, such as clips of cell-phones. The plastic flow pattern of the billet inside the die cavity is analyzed using a commercial finite element package “DEFORM 3D”. The Module of Die Stress Analysis in the finite element software “DEFORM 3D” is also used to simulate the stress, strain, and the displacement distributions of the die during extrusion of clips of cell-phones. The extrusion load, the stress and strain distributions of the die, the temperature distribution, and thickness distribution of the extruded product are investigated. Furthermore, hot extrusion experiments using A6061 as the specimen are executed. The experimental results of temperature, thickness distribution of the product, extrusion force, etc, are compared with the analytical values to verify the validity of the proposed die design guideline.

Effect of Extrusion Strain Path on Microstructure and Properties of AZ31 Magnesium Alloy Sheet

The mechanical properties of AZ31 magnesium alloy sheets processed by different extrusion strain paths were examined in correlation with concurrent microstructure and texture evolution. The conventional extrusion (CE) and asymmetric extrusion (ASE) paths were performed on Mg alloy sheets. The textures at near surface and mid-layer of ASE sheets were various throughout sheet thickness direction as a result of extra asymmetric shear strain. This can stimulate the orientation of (0002) basal planes to incline approximately 12° toward the shear direction. Moreover, the basal texture of ASE sheet was weakened compared with CE one. Enhancing the ambient formability of extruded Mg alloy sheet fabricated by ASE path was accomplished by the tilted weak basal texture.

Strain and texture in friction extrusion of aluminum wire

Friction extrusion is a solid-state process that can produce high quality, fully consolidated wire or rod directly from metal chips, powder or billet. However, little is understood regarding the variation in material flow or extrusion strain with changes in processing parameters. Extrusion strain level may be of great import in determining whether or not the charge is fully consolidated. In order to explore the material deformation behavior during this process, flow visualization experiments were conducted using AA6061 billets with AA2195 as a marker insert. Variations in material flow during a single extrusion were documented and correlated with changes in grain size, which has previously been correlated with extrusion temperature. Marker shape was used to make an approximation of imposed strain during the extrusion as a function of relative extrusion temperature. Also, tests using various extrusion forces and die rotation speeds were conducted. The influence of extrusion parameters on deformation evolution was elucidated and discussed. Grain orientation analysis conducted using electron backscatter diffraction showed a fully recrystallized microstructure with weak texture indicating that recrystallization was likely a static process occurring after passage of the wire through the die. Key findings include: (1) longitudinal strain is solely a function of overall reduction (2) in plane shear strain decreases with increasing extrusion temperature, and (3) with increasing extrusion temperature, friction extrusion becomes similar to normal extrusion.

Preseismic deformation in the seismogenic zone of the Lushan M S7.0 earthquake detected by GPS observations

A continuous GPS array across the southern segment of the Longmen Shan fault zone recorded the deformation during the process of the Lushan MS7.0 earthquake that occurred on April 20, 2013. Such data can provide meaningful information regarding the dynamic evolution of crustal deformation in the seismogenic zone. Our studies have shown that the occurrence of the Wenchuan earthquake led to the loading of compressive and sinistral shearing strain on the southern segment of the Maoxian-Wenchuan fault, whereby the extrusion strain accumulated at a greater rate than before the Wenchuan earthquake. The strain time series in the seismogenic zone revealed that the principal compression strain rates decreased from west to east in the direction of N30°–45°W. Furthermore, the area to the east of Beichuan-Yingxiu fault behaved as a zone of compressive deformation with obvious sinistral shearing deformation. The surface strain and the first shearing strain time series decreased with time, while the area to the west of the Beichuan-Yingxiu fault behaved as a zone of dextral shear deformation that increased with time. Furthermore, the regional deformation field before the Lushan earthquake showed that the rate of extrusion strain accumulation in the southern segment of the Longmen Shan fault zone was obviously larger than before the Wenchuan earthquake. Moreover, the sinistral shearing strain accumulated in the area of the southern segment of the Maoxian-Wenchuan fault. Based on the above analysis, we consider that the eastward movement of the Bayan Har block increased considerably following the Wenchuan earthquake, which enhanced the accumulation of compression strain in the southern segment of the Longmen Shan fault zone.

Microstructure evolution and strengthening mechanisms of cold-drawn commercially pure aluminum wire

The tensile strength of cold-drawn commercially pure aluminum wire shows an obvious three-stage characteristic, including the first strengthening stage, steady stage and second strengthening stage, with increasing extrusion strain. The dislocation density, intensity of 〈111〉 texture and percentage of high-angle grain boundaries are apparently increased in the second strengthening stage. Consequently, the final strengthening mechanisms may be well explained by the existence of the high-density dislocation, the 〈111〉 texture and high-angle grain boundary.

Modeling of Static and Geometric Dynamic Recrystallization during Hot Extrusion of Al-Mg-Si Alloy

Under certain conditions of extrusion temperature and strain rate Al-Mg-Si alloys produce coarse recrystallized grains at and near the surface. Current FEM models are able to analyze grain size evolution for extruded profiles, but cannot predict the coarse recrystallized grains near the surface. A new model using DEFORM 2D and local state variables such as strain, strain rate and temperature is compared with Al-Mg-Si rods extruded at 440°C and 500°C for two extremes of strain rate. The model is found to be sensitive to the processing conditions and to accurately predict the recrystallized grain size and fraction.

Grain size evolution simulation in aluminium alloys AA 6082 and AA 7020 during hot forward extrusion process

The present paper investigates the grain size evolution in aluminium alloys AA 6082 and AA 7020 during hot forward extrusion process. The aim of the present work is the definition and implementation of a predictive algorithm that is able to compute the evolution of the grain shape during the process within the finite element method code Deform. Extrusion experiments were performed at two levels: at reduced scale for investigating and identifying the predictive equations and at industrial scale for validating the developed algorithm. At small scale extrusion, a complete factorial plan was performed for two alloys at three different temperatures, three extrusion ratios and two ram speeds: the discards and extrudates from the experiments were quenched immediately in order to avoid any potential recrystallisation, hence allowing measurements of transitional processing steps. At the industrial scale, instead, the 7020 alloy was extruded with two different die designs, thus producing a 20 mm diameter round bar under different extrusion ratios and strain paths. Finite element simulations were initially validated over visioplastic investigations in order to establish an accurate computation of the material flow, then experimental and numerical results were coupled, thus allowing the definition of the grain evolution model that was successfully integrated and validated on industrial scale trials.

On the factors influencing the extrusion strain, particle size and dissolution behavior of multiparticulate systems obtained by extrusion/spheronization

Abstract The increased need for predicting the properties of granular systems has become a growing challenge for the pharmaceutical industry. Experimental design has hastened developments in the field of pharmaceuticals and helped scientists to better understand the behavior of particles in the wet granulation process. In this research, the production of pellets containing binary mixtures of high-dose paracetamol (40, 60 and 80%) and microcrystalline cellulose (Microcel® MC 101) was evaluated. Three commercial grades of the drug at three concentrations each were used. Pellets were prepared by axial and radial extrusion systems and then spheronized. The formulation and process, as input variables, were analyzed using a response surface methodology (RSM). The responses considered as output variables were energy spent on the extrusion, particle size distribution of the granules and the parameters of the Weibull function, time ( τ d ) and shape ( β ), in terms of dissolution behavior. The results indicated that less energy is spent during the radial extrusion process for commercial-grade paracetamol with 80% of drug and fine particle size. Also, these conditions resulted in a higher percentage of the pellet being in the main size fraction (0.800–1.250 mm) and a larger time required to dissolve 63.2% of the drug ( τ d). It was observed that the τ d value decreased with increasing particle size of the powder formulation. The β parameter was strongly influenced by the drug load and paracetamol grade for both extrusion procedures. The higher the content (percentage) and the smaller the particle size of the drug the higher the β parameter, indicating a parabolic shape changing to sigmoidal shape for the behavior of this parameter. These findings concerning formulations containing paracetamol can be extended to other drugs of equivalent particle size and water-solubility. The RSM tool was able to identify the manner and amplitude of the effects of the input variables on the output variables studied.

The effect of material grain structure on the surface integrity of components processed by microwire electrical discharge machining (μWEDM)

The machining response of metallurgically and mechanically modified materials when processed by employing the microwire electrical discharge machining (μWEDM) technology is reported in this paper. In particular, the effects of the material microstructure on resulting surface integrity of Al5000 series aluminium alloys after μWEDM processing is studied. The machining response of an ‘as received’ aluminium alloy was compared against the results obtained on samples processed through extrusion strain hardening and severe plastic deformation. Especially, the process–material effects on the resulting microhardness, phase content changes, heat-affected zone, surface roughness, microcracks, recast layer, material removal rate, and element spectrum after both rough and finishing μWEDM cuts were investigated. This study shows that an ultrafine grained (UFG) Al5083 exhibits not only superior mechanical properties but also the machining response to μWEDM is favourable. A reduction of the recast layer after μWEDM was observed when compared with ‘as received’ and ‘conventionally’ processed Al5083.