Papers by Keyword: Hot Extrusion

Abstract: In this study, the relationship between microstructures and mechanical properties of the extrusion processed Al-15wt.%Mg2Si composite was investigated after applying various extrusion ratios (6:1, 12:1 and 18:1) and solution treatment. Various techniques including metallography, tensile testing and SEM fractography were utilized to characterize the mechanical behavior of the MMC. Results demonstrated that extruded and heat treated composite possesses considerably higher strength and enhanced ductility in comparison with the as-cast samples. It was also found that heat treatment and extrusion processes do not change the primary Mg2Si morphology considerably, but its size increases as extrusion ratio decreased. Heat treatment and extrusion ratio effects on tensile strength, elongation of extruded specimens were also studied in this work.

Abstract: The TiB2/AZ31 magnesium matrix composite was fabricated via self-propagating hightemperature synthesis (SHS) and then hot extruded. The influence of hot extrusion on the microstructure and property of TiB2/AZ31 composites was investigated. The results show that hot extrusion and synthesized TiB2 particles could refine the grain size obviously. The synthesized TiB2 particles are micro- and nano-sized, dispersing homogenously in the matrix. The interface between the matrix and the particles are good bonding. Meanwhile, slip and twinning are the main deformation modes during the hot extrusion. The fracture surface of hot-extruded TiB2/AZ31 magnesium matrix composite has more dimples than the as-cast AZ31 magnesium alloy. The improvement of microstructure seems to be beneficial for the fracture ductility of TiB2/AZ31 magnesium matrix composite.

Abstract: A new micro-forming method, combining a metal’s super-plastic behavior with hot extrudsion technology, has been developed for manufacturing micro-gear from brass H62. The micro-gear, which modulus m = 0.125mm, pressure angle α = 20°, number of teeth z = 6, tip diameter d = 1mm, was selected and its dies were designed with a better die approach angle based on the DEFORM-3D FEA simulation results of the hot extrusion process. Finally the micro-gear was successfully hot extruded at 650°C from blank Φ3mm×3mm with extrusion ratio about 17. A good dimensional accuracy for micro-gear was obtained by using this hot extrusion technology. In the special die set, the split die structure was designed, and the special die materials were chosen, such as the pressure ram was made of tungsten carbide, and the other dies were made of mold materials 4Cr5MoSiV1.

Abstract: The rigid-visco-plastic finite element model for the hot forging process of transmission shaft flange yoke was established, and two forging schemes of different male die shapes were simulated. As for the present forming process, the forming defects were indentified and analyzed. Based on the simulating results the decision-making process was obtained, and a preforming die and a final forming die with proper structures and longer life were designed. The transmission shaft flange yoke part produced by this process is excellent in dimension tolerance and mechanical property. This process is profitable reference for producing the similar type of forks with complex shape.

Abstract: A typical parameterized model of pipe axis’ secondary necking in hot extrusion process was built，and the evaluation index of forming effect was proposed. Through using revised constitutive equation in Ansys model combining the method of numerical simulation, several mainly hot extrusion process parameters’ influence on forming effect were analyzed, such as friction, temperature and extrusion speed. The prediction equation of forming effect was worked out by numerical fitting, which provided a feasible way to get the better parameters in hot extrusion process. The experiment shows that the parameters obtained from equations can have a good guide on pipe axis and also other similar workpiece’ s hot extrusion process.

Abstract: Cu-Al2O3 composites were prepared by a new simplified internal oxidation process integrating with powder metallurgical process, and then the hot extrusion and the cold rolling processes were carried out. The microstructure, electrical conductivity, hardness, tensile strength and thermal stability of the composites were investigated. The results show that Cu-Al2O3 composites were fabricated successfully by the simplified process in which internal oxidation completed during the sintering. There are a mass of fine Al2O3 particles in size varying from 5 nm to 20nm dispersed in copper matrix after sintering 950 for 4h. After sintered at 950 for 4h and extruded at 950 followed with the cold deforming of 80%, the electrical conductivity, hardness, tensile strength and softening temperature of composite reach 81％IACS, 137HV, 561MPa and 850 respectively. It is considered that the dispersion strengthening and strain hardening have greatly contribution to the Cu-Al2O3 composites fabricated with the simplified process.

Abstract: A two-dimensional axi-symmetric finite element model for the tube hot extrusion process was developed based on Deform-2D software by consideration of the billet transfer, glass lubrication and the constitutive characteristics of IN 690 superalloy. An enhanced technique for adaptive mesh refinement (AR) is used to solve the large deformation problem. This model was then used to study the effect of boundary conditions and process parameters in tube hot extrusion. The Non-uniform deformation index as the representative parameter, which denotes the non-uniform deformation during the steady state of tube hot extrusion, is presented accordance to the feature of metal flow at deformation zone. The bigger of Non-uniform deformation index, the worse of non-uniform strain distribution. When the non-uniform deformation index getting smaller, the equivalent strain distribution along the length and cross section become more uniform and better product quality could be obtained. An increase in the billet and die preheating temperature could reduce the non-uniform deformation index individually. But the billet and die preheating temperature should not be too high. The increase of friction coefficient, the non-uniform deformation index also increased, which indicate appreciable results of metal flow. With the ram speed increase, the non-uniform deformation index decreases, but too fast speed is inadmissibility.

Abstract: The purpose of this research is the development of a high strength α-β brass (Cu-40Zn) with additions of elements of small solid solubility in brass. Cu-40Zn with 0.6 wt.% Tin (Sn), 0.73 wt.% Chromium (Cr) and 0.51 wt.% Iron (Fe) were prepared by casting (Cu-40Zn-CrFeSn). The yield stress (YS) and ultimate tensile stress (UTS) of extruded Cu-40Zn-CrFeSn was 291 MPa and 601 MPa, 23 % and 36 % higher than that of extruded binary Cu-40Zn alloy. Vickers micro hardness of 158 Hv was higher than that of extruded Cu-40Zn alloy (131 Hv). In addition, the elongation of extruded Cu-40Zn-CrFeSn was 35 %. The strengthening mechanisms of these alloys were considered as follows; one was a solid solution strengthening of Cr, Fe and Sn additives which were identified by SEM-EDS. The other was increasing of the area ratio of β-phase in Cu-40Zn-CrFeSn, compared to that of Cu-40Zn.

Abstract: Spray deposition is a novel process which is used to manufacture rapidly solidified bulk and near-net-shape preforms. In this paper, Al-8.6Zn-2.6Mg-2.2Cu alloy was synthesized by the spray atomization and deposition technique. The microstructural development during subsequent hot extrusion, hot rolling and canned forging was investigated by means of scanning electron microscope and X-ray diffraction. The results indicate that the spray-deposited alloy exhibits a uniform microstructure composed of the Al matrix and Mg(ZnCu)2 compounds with various shape. The fragmentation of the Mg(ZnCu)2 phases in the alloy has been regarded as one of the main phenomena during extrusion, rolling and forging. Under T6 temper condition, the hot-extruded Al-Zn-Mg-Cu alloy displays superior strength, and higher than hot-rolled and canned-forged ones.

Abstract: This study involves analyses and experiments of hot extrusion of magnesium alloy strips. Hot compression tests were firstly conducted to obtain the magnesium alloy’s plastic flow stresses at high temperatures. These data are used in the finite element simulations of the thin strip extrusion process. Using the FE simulations, the flow pattern of the magnesium alloy billet within the die, the temperature variation and the thickness distribution at the die exit were analyzed. The effects of different die bearing height design, initial billet temperatures and ram speed on the extrusion load, the temperature at the die exit and the product thickness distribution were also discussed. Finally, hot extrusion experiments were conducted and the experimental values of the extrusion load and dimensions of the products were compared with the analytical values to validate the analytical model. Sound products were obtained using the best designed bearing heights and other appropriate extrusion conditions.