Papers by Keyword: Hydrostatic Extrusion

Abstract: In order to obtain high performance magnesium alloy thick-walled tubes, the magnesium alloy ingot was extruded by hydrostatic shrinkage extrusion technology. Through a series of experiments, it was found that the magnesium alloy tube was not formed in the extrusion ratio that is smaller than 2.11 . Deform-3D software was used to simulate the tube forming process under different extrusion ratios. It was noting that at the condition of the extrusion ratio of 2.11, the equivalent stress and strain of the extruded tube at the fixed sizing zone were obviously unevenly distributed, which was disappeared with the increase of the extrusion ratio. Compared with the homogenized magnesium alloy , the yield strength, the tensile strength and the elongation were improved when the tensile test was carried out on the extruded magnesium alloy thick-walled tube. These results clearly showed that the mechanical properties of magnesium alloy tubes were improved after hydrostatic extrusion.

Abstract: The study is aimed at comparing the changes which occur in the microstructure and thermo-physical properties of pure copper (99.9%) and when copper alloyed with chromium and zirconium subjected to severe plastic deformation (SPD). The plastic deformation techniques employed were hydrostatic extrusion (HE), equal channel angular pressing (ECAP), and a combination of these two processes. The materials thus obtained had an ultra-fine-grained structure with the thermo-physical properties differing from those of the untreated materials. It appeared that there is a correlation between the deformation method employed and the thermo-physical properties of the materials, such as diffusivity and specific heat.

Abstract: The corrosion behavior of hydrostatic extruded tube AZ80 magnesium alloy was investigated by polarization curves and electrochemical impedance spectroscopy (EIS) in simulated atmosphere. The results indicated that, the corrosion resistance of the hydrostatic extruded AZ80 magnesium alloy with uneven deformed grains and increased sub-grains were obviously weakened, with larger corrosion current density in the polarization curves and lower corrosion resistances in the electrochemical impedance spectroscopy plots. This was mainly because of the hydrostatic extrusion which made AZ80 magnesium alloy within large numbers of dislocation tangles. So the residual stress increased the electrochemical activity of magnesium alloy which reduced the corrosion resistance of magnesium alloys.

Abstract: Magnesium wrought alloys are of special interest for structural components owing to their improved microstructures and mechanical properties by comparison with Mg cast parts. However, the market of Mg wrought alloys is still relatively small and one of the most important limitations for their application in areas such as aviation and spaceflight is that their strength is still not high enough to be widely used. Currently, more and more attention are paid to hydrostatic extrusion of Mg alloys because the extruded Mg alloys which exhibit extremely fine grains and high strength can be easily obtained by hydrostatic extrusion process. This review detailed the microstructures and mechanical properties of various wrought Mg alloys subjected to hydrostatic extrusion. Furthermore, numerical simulations and processing parameters optimization of the hydrostatic extrusion were also discussed. Finally, the current problems and development trends of hydrostatic extrusion of high-strength Mg alloys were also put forward.

Abstract: Grain size refinement is an efficient way to improve mechanical strength and thus make light metals even lighter in terms of specific strength. However, the strength improvement is at the expense of ductility. Therefore, a better understanding of microstructural factors influencing both parameters is of prime importance for further development of ultrafine grained materials. In this work, we report results obtained for 5483 aluminium alloy which was subjected to several severe plastic deformation (SPD) methods, i.e. equal channel angular pressing (ECAP), Hydrostatic Extrusion (HE) and the combination of the two. Detailed microstructural analysis revealed significant difference in the grain size and grain boundary characteristics between samples obtained following different routes. It was found that although the grain size is a prime microstructural parameter determining mechanical strength, second order factors such as grain size distribution and distribution of grain boundary misorientation angles also play a significant role.

Abstract: In this study, a Hydro Co-Extrusion Process of Al-Mn/Al-Si hybrid alloys prepared by electromagnetic duo-casting was investigated. Sleeve of the duo-casted billets is 3003 Al-Mn alloy and core is 4004 Al-Si alloy. It is expected hydrostatic stress during the HCE process enhances formability of materials and minimize any defects in extruded billets due to different material properties between two Al alloys. The duo-casted billet was extruded at temperature of 423K and with extrusion ratio of 5. Finally, the effect of the HCE on microstructure of the billet was investigated by an optical microscope.

Abstract: In this work, the superplastic behavior of AZ31, AZ61 and AZ80 magnesium alloys was investigated. The alloys were hydrostatically extruded at only 150 °C to get fine grained microstructures (−2, 10⁻³ and 10⁻⁴ s⁻¹. It was found that all alloys exhibited superplasticity at 200 °C, 175 °C and 225 °C for AZ31, AZ61 and AZ80 alloys, respectively. Low temperature dynamic recrystallisation played an important role for generating a finer and homogeneous microstructure during testing which enhances the deformation behavior of the alloys at these temperatures.

Abstract: The effect of different hydrostatic extrusion ratios on the microstructure and mechanical properties of the ZK60 magnesium alloys were investigated. The results showed that, the major deformation mechanism of the alloy is twinning at room temperature, which resulted in that the tensile strengthen and hardness of the extruded alloy improved greatly. With deformation ratio increasing, the ultimate tensile strengthen and hardness are linearly increased, with the functions of Y= 4.2X+358.3 and Y=2.3X +73.69, respectively. And the maximum tensile strength and hardness of the extruded alloy are 383 MPa and 87HB, respectively. But the elongation decreases obviously, the minimum decreasing degree is 50%. With the deformation ratio increasing, the tendency of elongation rate increased as an “M” model.

Abstract: In this study, Al/Cu composite was produced by hydrostatic extrusion process at 523 K. Mechanical and electrical properties of Al/Cu composite were investigated during isothermal aging. Microstructure observation and composition analysis of the interface was carried out scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), respectively. Three kinds of intermetallic composites are observed and they have increased in size as a function of annealing process. Their growth brings about the decrease in the hardness Al/Cu composite.

Abstract: In the present study, SPD processing was combined with annealing in order to obtain synergic effect of grain size refinement and precipitate strengthening. Samples of 7475 alloy were solution heat treated, water quenched and then subjected to hydrostatic extrusion with a total true strain of about 4. Hydrostatic extrusion resulted in a significant grain refinement from 70 mm to about 70 nm. The samples were subsequently annealed at temperatures inducing the formation of nano-precipitates. The investigations of the structure and mechanical properties of the samples subjected to SPD and annealing revealed different precipitation path in micro- and nano-grained samples. Also, it was found that the combination of HE processing and low temperature annealing results in the formation of nano-precipitates in nano-grained structures which effectively strengthen nano-aluminium alloy.