Papers by Keyword: Forward Extrusion

Abstract: Forward rod-backward can combined extrusion test was used to investigate the tribological properties of Ti-6Al-4V titanium alloy with oxide film at cold and warm forging conditions. 0.08 and 0.10 µm-thick oxide films were formed on the test piece by atmospheric oxidation treatment. A friction test was performed without using lubricants. As a result, the oxide film was effective to prevent seizure at cold forging condition, where the friction coefficient was estimated as about 0.15. However, at warm forging condition, a decohesion of the oxide film and seizure occurred, where the estimated friction coefficient was larger than that at cold forging condition. Furthermore, thickening the oxide film was effective against the decohesion and to reduce the friction coefficient.

Abstract: Selected ductile fracture criteria are introduced and applied to prediction of chevron crack initiation and development during forward extrusion of long shafts. We present the calibration of selected criteria for carbon steel, simulate the process of forward extrusion and compare the simulation results with real experiments realized in a cooperating industrial company.

Abstract: This paper presents the results of an investigation of the effects of homogenizing heat treatment and extrusion on plasticity of the as-cast AZ80 magnesium alloy. Both the homogenized and non-homogenized billets of AZ80 alloy were forward extruded at several different temperatures and different extrusion ratios. The effects of homogenization and extrusion on plasticity were evaluated by conducting tensile tests on these billets at room temperature and comparing their elongations. The experimental results showed that the elongation of the as-cast AZ80 alloy was increased by 67% after the homogenization treatment. After extrusion, the elongation of both the homogenized and non-homogenized AZ80 alloy increased significantly. The elongation of the homogenized billets decreased gradually with increasing temperature. For the non-homogenized billets, however, the elongation decreased sharply with temperature from 300 to 350 °C and then increased gradually with increasing temperature. There was not clear correlation between the elongations of both the homogenized and non-homogenized billets and the extrusion ratio.

Abstract: Material flow pattern in extrusion is an important part of the forming process. Understanding and formulating the material flow helps to determine the optimum shape of the die and important details of the process. In this paper, physical modelling of forward extrusion of non-symmetric L-shape section has been carried out to obtain an experimental understanding of the material flow pattern. A theoretical formulation using the conformal mapping theory has also been presented to predict the material flow pattern. The conformal mapping function was set up to translate the non-circular cross-section region of special-shaped products into unit dish. The results for the material flow pattern for the forward extrusion of L shaped profile from circular billets are presented here. In the physical modelling tests plasticine was used as the model material and different coloured layers of plasticine were used to build up the billet. Experimental and theoretical results were compared and good agreements were observed.

Abstract: Finite Element Method (FEM) has becoming more influences in analyzing and solving metal forming problems from the beginning of punch and die designed up to setting the appropriated surrounding constrains in the deformation processes. This research was concerning about the study of simulation in cold forward bar extrusion of some aluminum alloys reinforced with ceramic particles using a commercial FE program; MSC. Marc to enhance the analysis. Two most important parameters in extrusion were investigated, which included area reduction ratio, εA, and die angle, 2∂, that affected to the forming force in the workpiece. In this research, the matrix part of composites studied was varied as follow: AA6061, AA6082 and AA230A reinforced by particles of SiC and Al₂O₃. Also, the volume fraction of reinforcement was another material parameter needed for the study. The dimension of initial billet in the simulation had 24.7 mm of diameter and 30 mm of length. The punch and die were assumed to be rigid which neglected the deformation. In case of heat dissipation, they were not considered in this simulation; therefore, the process assumed to be done isothermally at room temperature of 20°C. From the modeling results, the suitable conditions for different parameters were obtained, which assisted to the consideration of appropriated forward bar extrusion processes of such particulate reinforced Metal Matrix Composites (MMCs).

Abstract: The forward extrusion experiments of homogenized AZ80 magnesium alloy were conducted in the extrusion temperature range of 300°C to 420°C and extrusion ratios between 15 and 75 to study the effect of plastic deformation on the mechanical properties and microstructure. The microstructure and mechanical properties of extrudate were measured by tensile tests and optical microscopy. The results demonstrated that the alloy grains were small, and small amounts of black hard and brittle second-phase precipitated at 330°C. When the extrusion temperature was up to 390°C, the grain size increased significantly, but the second phase precipitation became continuous. And then, in the case of the extrusion ratio of 60, the tensile strength of the alloy reached the peak value of 390 MPa. Inhomogeneous precipitation of the second-phase increased with the increasing of extrusion temperature. At the same temperature, the tensile strength increased firstly and then decreased with increasing extrusion ratio. With the gradual increase of the grain refinement, the dispersed precipitates increased and the tensile strength and plasticity reached their peaks when the extrusion temperature was 390°C. As the grain grew, the second phase distribution became inhomogeneous, and the strength and plasticity gradually decreased.

Abstract: In this work severe plastic deformation (SPD) technique was applied to produce bulk nanostructure material. The ECAP has been used on 6082 type low alloyed aluminium material. Some special compression tests and the forward extrusion technology were used to investigate the further workability of the nanostructured aluminium alloy. This work also includes also the design and manufacture of the forward extrusion die set.

Abstract: Samples of AZ31 wrought magnesium alloy are hot extruded into forward direction with various initial billet temperatures and extrusion ratios (ERs). Usually the insufficient room temperature formability of magnesium wrought alloys makes processing steps like rolling, extrusion etc. difficult, thus limiting their use for rolled or wrought parts. However, in this paper experiment is preformed under the hot forward extrusion process for AZ31 wrought magnesium alloy with different important parameters. Major process parameters such as punch speed, billet temperatures and ERs are considered and applied to the hot extrusion process with a constant value of the die land. The influence of different billet temperatures and ERs on the hot forward extrusion process is investigated and analyzed in terms of the grain flow, microstructure, grain size and hardness distribution of formed part for magnesium and Mg alloy. Maximum forming loads for various main parameters is tackled and checked to know the optimum forming load for hot forward extrusion process. Also finest grain sizes and an inhomogeneous microstructure of extruded parts seem to occur near the die land of tool-set due to the anisotropic plastic behavior during the hot extrusion process. Extrusion properties such as extrusion load, grain size, micro hardness and surface quality are compared between the main parameters during the hot forward extrusion process. In addition it is easily disclosed from the experiment results that the die land designed for safe tool-set plays a key role in improving the mechanical properties of formed product during hot forward extrusion process for AZ31 magnesium alloy.