Mechanics of single pass equal channel angular extrusion of powder in tubes (original) (raw)
Related papers
2009
The process of powder compaction through Equal Channel Angular Extrusion (ECAE) at room temperature was modeled using the finite element analysis package ABAQUS. Two powder compaction models, the Gurson model and the Duva and Crow model, were used to test their efficacy in modeling this process. Modeling parameters like friction coefficients, interaction conditions were determined by comparing the simulations for solid billet and an empty can with actual experimental runs for loads, shear angle and workpiece geometry. The simulations using the two models showed no significant difference in the stress in the powder during the extrusion. 2-D simulations were used to show the efficacy of two passes of ECAE in achieving full densification in the extruded workpiece. The results obtained from the simulations were also compared to experiments conducted to compact copper powder with a size distribution of 10μm to 45μm. It was found through experiments that the powder does not fully consolidate near the outer corner of the workpiece after the first ECAE pass and the results from the simulations were used to rationalize this phenomenon. Modifications made to the process by applying a back pressure during the simulations resulted in a uniformly compacted powder region. It was also found that the loads required to consolidate a powder through ECAE are much lower than conventional pressing or compression to achieve the same amount of compaction.
Lecture Notes in Mechanical Engineering, 2019
Semi-solid extrusion of Al-Cu-Mg Powder Metallurgy (P/M) alloys had simulated under three different temperatures and extrusion angles in the present investigation. Al, Cu, and Mg powders were taken in different ratios in order to produce strong and light weight P/M alloys. Billets were prepared with an aspect ratio of one (u 15 Â 15 mm) to get good deformation results. Al-4Cu-0.5Mg alloy composition was optimized to do semi-solid extrusion after considering density, hardness, and strength as best parameters to optimize. Alloys were sintered at 550 °C and prepared samples with Initial Relative Density (IRD) of 90% for densification and deformation studies. The working temperature range for semi-solid extrusion test was derived from TG/DTA analysis. Extrusion tests were performed on a hydraulic press under different deformation temperatures (550, 575 and 600 °C) and different solid fractions (0.93, 0.76, and 0.56) respectively. All the extrusion tests were performed with a low extrusion ratio of 1.44, die approach angles of 30°, 45°, and 60° and strain rate of 0.1 s −1. High density (>95%) and high hardness (>1000 MPa) extruded Al alloys were produced with good microstruc-tures. Microstructural analyses were done for all Al alloys and found uniform distribution of grains at different temperatures. Dynamic recrystallization of grains was found with increasing liquid fraction during extrusion experiments. For an accurate prediction of microstructure evolution the strain rate, strain and temperature have to be considered and these can be calculated by FEM simulation. Simulation studies had been performed at three selected temperatures using Deform-2D software. Simulation and experimental results have been shown good agreement between them.
Structural Properties Evaluation of Semisolid Extruded Al-Cu- Mg Powder Metallurgy Alloys
Transaction of Indian Institute of Metals, 2019
Structural properties evaluation of semisolid extruded Al-4Cu-xMg alloy preforms have been performed in the present investigation. Pressureless sintering of Al-4 wt% Cu with varying Mg (0, 0.25, 0.5, 0.75 and 1 wt%) powder mixture was performed in an inert atmosphere. The sintering behavior and mechanical properties of all alloys were investigated at different temperatures and compositions, respectively. The maximum density and hardness (647 MPa) were found in the Al-4Cu-0.5 Mg composition sintered at 550 °C. Semisolid extrusion was carried out on sintered Al-4Cu-0.5 Mg alloys having an Initial Relative Density of 80% and 90% to find the structure-property correlation due to deformation. Extru-sion was carried out in between solidus (542.7 °C) and liquidus (662.8 °C) temperatures with different solid fractions , which were derived from the TG/DTA analysis. All experiments were performed with low extrusion ratio of 1.44, strain rate of 0.1 s-1 and die approach angle of 30°. Structure-property correlation study of extruded rod was performed at front end, middle part and rear end to understand the temperature and metal flow profiles during deformation process. There were no visible defects found in the demarcated samples. The presence of Al 2 Cu precipitate in the extruded alloy was identified by X-Ray diffractometer and scanning electron microscope with energy dispersive spectroscopy analysis. The microstruc-tural evolution was observed in all the extruded bars by optical microscope. Micro-hardness of extruded samples was found to be 1001 MPa, which was almost two times of sintered sample.
The Efficiency of Twist Extrusion for Compaction of Powder Materials
Powder Metallurgy and Metal Ceramics, 2019
Within the theory of plasticity for porous bodies, the compaction of titanium powders by twist extrusion and uniaxial pressing in rigid dies was qualitatively analyzed. It was shown that the strain dependence of porosity with twist extrusion reached the level that was inversely proportional to backpressure. Much lower pressure was found to be needed to achieve the same residual porosity of powder titanium billets with twist extrusion than with uniaxial pressing. Numerical estimates gave the following result for powdered titanium: when a residual porosity was 5%, the twist extrusion backpressure was one twentieth the pressure required with uniaxial pressing. The experimental studies for PT5 titanium powder confirmed the conclusions of the qualitative analysis carried out within the theory of plasticity for porous bodies. With increase in backpressure and in the number of twist extrusion strain cycles, the hardness of powdered titanium increased up to 140 HB, being quite close to 160 HB of cast commercially pure titanium. The experiment demonstrated that the hardness and density of the powder titanium billets after twist extrusion with a backpressure of 200 MPa practically reached their maximum. Therefore, a further increase in backpressure was unreasonable.
Key Engineering Materials, 2016
The paper is devoted to the development of a process of tubes extrusion from MgCa08 magnesium alloy. For optimization of extrusion process the Qform software was used. The numerical model of flow stress and fracture criterion for MgCa08 were obtained based on tension/compression measurements performed in a universal testing machine Zwick Z250. Predictions of the flow stress and deformations were modeled as well as the ductility of material. The process was optimized according to the plasticity and temperature criterions. In the optimization process, temperature of the billet and the speed of extrusion were determined. Based on the optimal parameters the extrusion of tubes with external diameter of 5 mm was performed in the laboratory press. On top of the macroscopic testing and calculations, investigations of the material microstructure and the micromechanical behavior of the material after the extrusion were performed by a combination of SEM and nanoindentation analyses. Micromecha...
Extrusion of the magnesium-nickel alloys
AIP Conference Proceedings, 2019
Gravity cast billets in AZ91 alloy and two experimental alloys containing Nickel (AZ91+Ni), were directly extruded. Chemical composition of the Nickel containing alloys was designed such that it corresponded to a potential recycling quality of the AZ91 alloy. Extrusion trials were performed at 370⁰C, applying extrusion speed of 2.6 mmin-1 and reduction ratios 4:1 and 6:1. Effective strain distribution in the extruded rod as a function of the distance from the rod center was in the range 1.6 to 7, depending on the applied reduction ratio. These values were determined by FEM-analyze. Extrusion of the experimental alloys was not challenged by rather large, cubic shaped Nickel-based particles present in the microstructure of the experimental alloys. The extrusion process of these led to extruded rods with smooth surface without extruded failures of type hot cracks. No effect of Nickel on mechanical properties of AZ91 alloy was noticed either. Tensile test showed that mechanical properties, Yield strength, Tensile strength and Elongation, were mainly driven by strain hardening and volume fraction of the brittle, precipitated -phase.
Effect of equal channel angular extrusion process on deformation behaviors of Mg-3Al-Zn alloy
Influence of different grain sizes on deformation behavior of Mg-3Al-Zn magnesium alloy was investigated by in-situ observation with scanning electron microscopic under uniaxial tensile loadings. The results indicate that there are the different deformation behaviors between coarse grains and finedgrains magnesium alloy by the two-step equal channel angular extruded (ECAE) technology. Why the elongation to be well improved and simultaneously why the yield stress to be slightly decreased are explained based on the different surface plastic deformed types and cavity evolution processes.
Production of Dense Compact Billet From Ti-Alloy Powder Using Equal Channel Angular Extrusion
The project was aimed at an investigation of the potential for cost-effective, efficient consolidation of pre-alloyed "PA" Ti-6Al-4V (HDH) powder at temperatures of 400?C and below using Equal Channel Angular Extrusion (ECAE), with applied back pressure. The limit on processing temperature was imposed to minimize the contamination of powder and compact with gaseous constituents known to be harmful to resultant properties. An analysis of existing published investigations of current processing techniques, most notably those involving hot isostatic pressing (HIP), reveals that relative densities of 98-100% can only be obtained at processing temperatures in excess of 800?C. For such methods, and temperatures below 400?C, the relative densities achievable are typically of the order of 77%, when starting with an initial ?tape? density of 63%. In this context, the project goals, of reducing the processing temperature of PA powder compaction below 400?C while achieving a relative ...
Effect of materials and temperature on the forward extrusion of magnesium alloys
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004
Magnesium alloys are being extensively used in weight-saving applications and as a potential replacement for plastics in electronic and computer applications. However, processing of magnesium has always been a challenge for manufacturing industries owing to their high brittleness despite their good EMI shielding property and high specific strength. Despite these advantages, they are limited by their processability. The present work aims to evaluate lower temperature formability of magnesium alloys. Three different materials were selected for axisymmetric extrusion tests, namely AZ31, AZ61 and the forging alloy, ZK 60. To establish the size and capacity of the press required to perform these forming trials and to know the formability, simulation using finite element analysis was carried on a representative material AZ31 using the properties established based on earlier work. A die set with a die shoe was designed to perform the forward extrusion trials. The area reduction ratio for forward extrusion was fixed at 41% for the die design and simulation. The maximum strain is given as ln(A o /A f ) ∼ 0.88 in the case of forward extrusion. The temperature was varied with a temperature controller built in-house from room temperature (RT) to 300 • C. However, the results provided below only include the tests carried out at RT, 100, 150, 175 and 200 • C. Although the forming trials were successful above 200 • C, there was difficulty in removing the specimens from the die cavity. Secondly, the process of removing the samples in the case of AZ31 and ZK 60 resulted in cracking, so it was difficult to evaluate the samples and the process. However, AZ61 samples did not show any evidence of crack formation during ejection of the formed sample. Simulation results and experimental trials showed that magnesium (AZ31) could be easily formed at elevated temperatures of 300 • C. Though there was a good correlation on the yield point prediction between simulation and experimental results, the extrusion loads were higher.
In-Depth Comparison of an Industrially Extruded Powder and Ingot Al Alloys
Metals, 2020
An industrial press was used to consolidate compacted aluminum powder with a nominal diameter in the range of 1 µm. Direct and indirect hot-extrusion processes were used, and suitable process parameters were determined from heating conditions, ram speeds and billet temperatures. For comparison, a direct-extrusion press for hot extrusion of a conventional aluminum alloy AA 1050 was used. The extruded Al powder showed better mechanical properties and showed a thermal stability of the mechanical properties after annealing treatments. To increase the theoretical density of the directly extruded Al powder, single-hit hot-compression tests were carried out. Activation energies for hot forming were calculated from hot-compression tests carried out in the temperature range 300–580 °C, at different strain rates. Processing maps were used to demonstrate safe hot-working conditions, to obtain an optimal microstructure after hot forming of extruded Al powder.