Papers by Keyword: Net-Shape Forming

Abstract: This paper reports friction-stir forming (FSF) of gear-racks of JIS A5083 aluminum alloy with semi-closed dies. FSF is a modified friction-stir process suggested by Nishihara in 2002. The process generates frictional heat and internal forces, enabling massive deformation of the material. It has been successfully utilized for mechanical joining and microforming, but seems to offer an opportunity for net-shape forming of bulk products as well. We put a material in a semi-closed gear-rack die and conducted friction stirring on its top surface. The material deformed and filled the cavity of the die due to high pressure and heat caused by friction stirring. This study investigates the forming conditions and the corresponding results, including the material fill ratio in the tooth. We also investigated the difference between this method and open-type FSF that had been conducted with an open-die structure.

Abstract: This paper reports observation of material flow in friction-stir forming of aluminum alloy gear racks. Friction-stir forming was newly developed by Nishihara and is dedicated for material forming. In the process, a material plate is placed on the die and friction stirring is conducted on its back surface. The material deforms due to high pressure and heat caused by the friction-stir process and deforms precisely to the shape of the die. The process has mainly been studied for microforming and mechanical jointing; however it was successfully utilized for net-shape forming of A5083 aluminum alloy gear racks. The authors observed the appearance of products, change of mark-off lines on its surface, and deformation of its longitudinal cross section by photo-processing. In addition, we evaluated the distribution of hardness in transverse cross sections of a product tooth. As a result, it was observed that the material did not flow in the transverse direction of the cavity of the gear-rack die, though more material filled at the retreating side than at the advancing side. The material filled the tooth-cavity mostly before passage of the tool probe over the tooth.

Abstract: Friction-stir-forming (FSF) of gear-racks of JIS A5083 aluminum alloy is reported in this paper. We put a material plate on a gear-rack die and conducted friction stirring on its back surface. The material deformed and precisely filled the fine cavity of the die due to high pressure and heat caused by friction stirring. This study investigates the forming conditions and the corresponding results, including the material fill ratio in the tooth. It is thought that the deformation volume of the material is key for the fill ratio, and the shoulder diameter of the tool in a single-pass process or the path area in a multi-pass process affects it as well.

Abstract: This paper proposes a new forming process for gear racks featuring a tooth-surface stiffening layer. The proposed process is as follows. First, a JIS A5083P aluminum alloy plate on which a surface modifier of WC particles and vaseline paste had been applied was put on a gear-rack die. Next, friction stirring was conducted on the back surface of the plate. The material then deformed and precisely filled the cavity of the die. WC particles were embedded into the surface of the aluminum alloy matrix due to high pressure and heat caused by friction stirring. The forming conditions and the corresponding results, including the distribution of WC perticles on the tooth surface, are investigated in the study. WC particles were embedded near the surface mechanically, and only a very few particles were observed inside the matrix. With an undefill condition, WC particles are concentrated on the rear surface of the tooth, which contacts the tail side of the die. In contrast, No significant particle density differences were observed among the profile of teeth with a fully filled condition in the die cavity.

Abstract: The microstructure and mechanical properties of as-cast ZK80 Mg alloy during net-shape forming of tensile specimens with close-die pressing extrusion, and the effect of extrusion-forging on the fracture mechanism of ZK80 alloys were studied in the present investigation. The results indicated that Rm (σ_b)、Re (σ_s) and A(δ) of compound forming ZK80 Mg alloy had noticeable improvement. Large deformation and produce twins, lead to grain refinement and had strongly influence on mechanical property of ZK80 Mg alloy, as well as strong affected the mechanical properties of the alloy. It was found that as-cast ZK80 Mg alloy has mixed fracture characteristics including cleavage fracture, intergranular facture and ductile fracture. As-extruded perform and as-close die ZK80 Mg alloys were obvious dimples for ductile fracture pore nucleation mechanism.

Abstract: The aim of this study is to establish the net-shape forming of titanium matrix composites (TMCs) shot sleeve for Al alloys die-casting using a casting route. In-situ synthesis and casting of TMCs were carried out in a vacuum induction melting furnace. The synthesized (TiC+TiB) TMCs were examined using an scanning electron microscopy and electron probe micro-analyzer. The thermo-physical variables estimated by casting process were applied to the modeling of TMCs shot-sleeve casting using the Magmasoft®. The results of the investment casting and modeling of TMCs confirm that the casting route can be an effective approach for the economic net-shape forming of TMCs shot sleeve.