Papers by Keyword: Backward Extrusion

Abstract: The development of light-weight materials and fabricating parts/sub-assemblies of substantially large dimensions has become a major issue for the aerospace industry, which has boosted the development of more advanced materials with high specification properties. Recent aluminum and magnesium alloys developments are based on achieving superior fatigue crack growth resistance, better corrosion resistance, lower density, etc. Standard manufacturing techniques, such as extrusion, ought to be developed in order to find a beneficial solution allowing for structural weight reduction, which is a very efficient means of improving aircraft performance. It is associated with the problem of extrusion profiles with a complex cross-section shape. In this work the formability of aluminum and magnesium alloys in the extrusion process was determined by the upsetting test through specification of the flow stress in relationship to the deformation size and rate. The results of the upsetting test of Al (7075, 2024, 8090, 2099) and Mg ( AZ31, AZ61, AZ80, WE 43) alloys were used in determining the conditions of the extrusion of profiles of various cross section shape and extrusion ratio. The analysis of macro and microstructure of extruded products and their mechanical properties demonstrates strong influence of the shape of extrudate cross section on metal exit speed and extrusion force value. Macro-and microstructure of all the investigated alloys after extrusion are highly homogeneous in terms of the grain size and morphology of the phase components, compared to the macro- and microstructure in the initial state, which justifies the use of them in production of aviation profiles.

Abstract: Body shell of anti-tank rocket which is a pipe part working under extreme conditions of high pressure and temperature, is manufactured from low-alloyed high quality steel 30X3MФ. The steel 30X3MΦ made in Vietnam appropriates of standard to produce body shell anti-tank rocket. The shell ensure technical requirements of composition, with very low rate of P, S and has good mechanical properties. After casting, steel billets were backward extrusion, includes 3 steps of thinned stamp, heat treatment and drawing processes, body shell fabrication is satisfied requirment of technique for anti-tank rocket shell. Results of fire testing of the body shells are in agreement with that of Russian ammunition. The body shells of anti-tank rocket which were manufactured in Vietnam conditions, satisfied desired technical requirement.

Abstract: A numerical simulation on the deformation behavior of AZ31 magnesium alloy during backward extrusion with counter pressure was investigated by FE software DEFORM. The results show that the steady load increases nonlinearly with the increment of counter pressure. The equivalent strain gradient decreases significantly results from the counter pressure and the unevenness in the top of wall disappeared approximately when the counter pressure is 10~15MPa. Furthermore, there are obviously shear band along the inner fillet to outer fillet of workpiece. Higher hydrostatic pressure generated with counter pressure compared that of no counter pressure leads to improve the plastic deformation limit. The damage factor is reduced significantly in the backward extrusion with counter pressure, which is beneficial to the improvement of crack.

Abstract: Provided here is a mathematical model of the operation of backward extrusion in the mode of short-time creeping of thick-walled pipe blanks made out of orthotropic material with cylindrical anisotropy of the mechanical properties. Carried out was theoretical research of the operation of isothermal axisymmetric backward extrusion of thick-walled pipe blanks made out of anisotropic materials by conic point-tool in the mode of short-time creeping. Established were regularities regarding the change of material flow kinematics, regarding the stressed and strained condition of the blank, regarding force modes and limit possibilities of deformation depending on the technological parameters, on friction conditions on the contact surfaces of the operating tools and of the blank, regarding the geometrical dimensions of the blank and of the manufactured part, and of the anisotropy of the mechanical properties of the blank material, that on the basis of the developed mathematical model of isothermal non-radial flow of anisotropic material under conditions of axisymmetric stressed and strained conditions in the mode of short-time creeping. Experimental operations were carried out for isothermal backward extrusion of thick-walled pipe blanks made out of АМг6 aluminum and ВТ6С titanium alloys. Comparing the results of theoretical and experimental data for force modes of the operation of isothermal backward extrusion of thick-walled pipe blanks points to their satisfactory similarity (difference not exceeding 5% - 10%).

Abstract: Mg batteries have received increasing attention mainly because of their high volumetric capacity (3832 mAhcm⁻³). In order to form type NO.5 cell packing for Magnesium battery the finite element simulation by Deform 3D was carried out. Then backward extrusion was conducted on an AZ31 magnesium alloy at 300°C. The results show that battery cell packing with the wall of 0.35 mm can be formed through backward extrusion with an AZ31 Mg alloys. A significant grain size refining was resulted from hot BE, however, the microstructure in different positions of the Mg cell packing was inhomogeneous. At bottom of the packing, the microstructure was formed by equiaxial and relatively coarse grains. The wall of the Mg cell packing was made of much finer grains.

Abstract: A backward extrusion forged bonding using low carbon steel and pure aluminum is conducted. The bonding strength between the materials is evaluated by a micro tensile test that is cut out at the bonding boundary. The maximum bonding strength is larger than that of the aluminum. In addition, the metallurgical mechanism of the joining of the backward extrusion forged bonding is investigated by means of a scanning transmission electron microscope (STEM). An intermetallic compound (IMC) layer is produced at the boundary with a thickness of about 3 nm. The process is applied for bonding between aluminum-nickel and between aluminum-copper. The bonding strength between the materials was evaluated by using a micro tensile test and the maximum bonding strength is shown. Fractured surfaces of the tensile specimens are observed by scanning electron microscope (SEM) and relationship between bonding strength and position on the boundary is discussed.

Abstract: FE analyses of backward extrusion of multiple micro-pins have been conducted to examine the effects of pin geometry, layout and spacing. The effect of friction on material flow and accuracy of pin geometry has been investigated. FE analysis was performed for a commercial grade Al1050 as well as its ultrafine grained version produced by severe plastic deformation allowing a comparison to be made. Pin layout plays a large role in achieving uniformity of pin height. Material starvation resulted in the central pins being shorter than the surrounding pins. Simulations without the centre pin were conducted, which resulted in increased pin height uniformity. Simulations with friction resulted in a greater uniformity of pin height but required a greater load. Using stronger ultrafine grained material increased the load and reduced the pin height uniformity.

Abstract: In this study, a novel process to forge thin walled products using bulk-sheet forming concept is developed to overcome drawbacks of a conventional multistage backward extrusion. A newly developed process design is suggested based on numerical analysis, and feasibility of one-stage forging process is discussed.

Abstract: The Mg-1.0Zn-xCa (x=0.2, 0.5, 0.8, 1 wt. %) alloys were prepared by zone solidification and backward extrusion technology. The microstructure and mechanical properties of backward-extruded Mg-1.0Zn-xCa alloys were investigated. The results showed that these backward-extruded Mg-1.0Zn-xCa alloys were mainly composed of equi-axed pentagon-shaped grains and some Mg_0.9Zn_0.03 precipitates. The tensile and compressive strengths of backward-extruded Mg-1.0Zn-xCa alloys were greatly improved. The improved mechanical properties are mostly attributed to fine grain strengthening, solid solution strengthening and precipitate strengthening. The results demonstrated that the micro alloying of Ca element was one of effective method to improve the mechanical properties of Mg-1.0Zn based biomaterials.

Abstract: A coupled numerical simulation between thermal-mechanical and microstructure evolution was realized through embedding the developed user subroutines into the FEM software DEFORM-3D system. Then the dynamic recrystallization fraction and average grain size of In718 alloy in cylindrical cup backward extrusion with different parameters was solved and analyzed. The complete dynamic recrystallization occurs in the middle of cylinder wall and the grain size is the finest. However, the grain size of top of cylinder wall changes less because of the less plastic deformation. Furthermore, higher speed of punch is useful to the DRX but it is not enough time to occur dynamic recrystallization completely with much higher speed of punch. In spite of more recrystallization occurring in the bottom, the grains grow in the cylinder wall so that much higher temperature goes against improving finer and uniform of grain size. Therefore, it is better for obtaining finer and uniform grain size with 1000(°C)-1050(°C) and 5(mm/s) in In718 alloy cylindrical cup backward extrusion according to the research.