Hamed Mofidi Tabatabaei

Cylindrical Pin Embossment on A5083 Aluminum Alloy Substrate Fabricated by Friction Stir Forming

This paper reports friction-stir forming (FSF) of cylindrical pin embossments on JIS A5083 aluminum alloy medium gauge plate. A substrate material was put on an emboss die and conducted friction stirring on its back surface. The die has 1mm diameter and 0.5mm deep fine holes at 1.5mm pitch on its top, and the material successfully filled them due to high pressure and heat caused by friction stirring. Three tools having different shoulder diameter were utilized to investigate the deformable area with a single pass. As a consequence, faster spindle speed, slower tool feed rate, and larger tool shoulder contribute to a wider range of completely formed pins. Extrusion of the material to the die cavity seemed to be mostly limited under the area of the shoulder. The ratios of the band width of the complete pins to the shoulder diameter were increased with the larger diameter of the shoulder of the FSF tool. Therefore, a larger shoulder was more effective for wide-range embossing with a single pass. In addition, we evaluated the shape of formed pins with a non-contact 3D measurement system. Accuracy of the height of the completely formed pins was within ±0.013mm, which was comparable with machining.

Friction Stir Forming of A5083 Aluminum Alloy Gear-Racks with WC Particles Embedded in Tooth Surface

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.

Friction stir forming for mechanical interlocking of insulated copper wire and Zn-22Al superplastic alloy

In this study, a novel method of friction stir forming (FSF) was conducted for mechanical interlocking of Zn-22Al superplastic alloy and thin copper wire insulated by polyimide. The potential development of a composite material capable of transmitting electrical energy or electric signals was studied experimentally, and it was concluded that FSF can successfully interlock insulated copper wire with Zn-22Al superplastic alloy. The authors suggest the possibility that FSF could join sheets of Zn-22Al alloy by pressure welding and superplastic forming and diffusion bonding (SPF/DB). Trials of FSF were carried out on a modified vertical milling machine. The results are discussed in terms of microstructure observations, hardness distributions, and temperature measurements.

Production of a Superplastic Vibration-Damping Steel Sheet Composite Using Friction Stir Forming

This study proposes a novel method of manufacturing composite vibration-damping steel sheet with Zn-22Al superplastic alloy using friction stir forming (FSF). Trials of mechanical interlocking of steel sheet with Zn-22Al superplastic alloy using FSF were carried out on a modified milling machine. The results are discussed in terms of residual microstructures and mechanical properties. We concluded that cladding steel sheet with Zn-22Al superplastic alloy using FSF results in superplastic forming and diffusion bonding.

Friction Stir Forming of Aluminum Alloy Gear-Racks

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.

Observation of Material Flow in Friction Stir Forming for A5083 Aluminum Alloy Gear-Rack

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.

Visualization of Contact-Pressure Distribution between Material and Backing Plate in Friction Stir Processing

In this study, the authors evaluated pressure distribution on a backing plate in friction-stir processing (FSP) utilizing an embedded pressure pin connected to a load sensor. They conducted FSP on aluminum alloy plates repeatedly offsetting the path-lines from the center of the pin and recorded change of forming pressure with tool position, which was compiled from the bearing load of the pin. The authors mapped the results to visualize the two-dimensional contact pressure distribution on a backing plate during FSP. They then compared the height distribution of the wall fabricated by friction-stir forming (FSF) utilizing a die having a groove with the observed distribution of pressure. Consequently, maximum pressure was observed beneath the rim of the tool probe at the retreating side (RS), and the highest points of the wall were observed at the RS.

Trials of Developing a Magnetic Aluminum Metal Matrix Composite through Friction Stir Spot Forming

In present study, possibility of developing a new magnetic aluminum-based composite material by using principles of friction stir forming (FSF) is studied. Friction stir forming is a new materials forming technique which uses frictional heat to plasticize and plastically deform the alloy. Local magnetizing and local hardening of A6061 aluminum alloy is discussed by attempts of embedding and dispersing iron oxide powder and steel balls into A6061 aluminum alloy through spotted friction stir forming. Experiments revealed that FSF can be used to mechanically interlock steel balls and iron oxide with aluminum alloy and develop an aluminum metal matrix composite with improved magnetic properties. Results are discussed in terms of microstructural observation, hardness and magnetic properties.

Friction Stir Forming for Mechanical Interlocking of Ultra-Thin Stainless Steel Strands and Aluminum Alloys

In this study, a novel method of mechanical interlocking of super-thin stainless steel strands with different aluminum alloys was conducted by using friction stir forming (FSF). The potential for the development of a multi-functional composite material was studied experimentally. It was concluded that FSF can successfully interlock stainless steel strands and different Al alloys and presents the possibility of improving the mechanical properties of the alloy. Trials of FSF were carried out on a modified vertical milling machine. The results are discussed in terms of microstructure observations, hardness distributions and tensile tests.

Evaluation of Material Deformability and Pressure Distribution on a Die Surface under a Tool in Spot FSF

Friction-stir forming (FSF) is a friction-stir process invented by Nishihara in 2002. In FSF, a material is put on a die, and friction stirring is then conducted on its back surface. The material deforms and precisely fills the cavity of the die due to high pressure and heat caused by friction stirring. Materials in the process often display outstanding deformability and moldability. However, behavior of the material during the friction-stir process has not been sufficiently clarified as a metal forming process. In this paper, material deformability under a tool in spot FSF, i.e. FSF without tool travel, was investigated employing a die having holes. The authors conducted spot FSF on 3mm-thick A5083P-O aluminum plates at offsetting points from the center of a hole and evaluated the height and volume of cylindrical extrusions to evaluate the deformability distribution under a tool. In addition, forming pressure distribution on the die surface was evaluated by an embedded pressure pin connected with a load sensor. The authors conducted spot FSF on 3mm-thick A5083P-O aluminum plates at offsetting points from the center of a pin as well as deformability tests and evaluated forming pressure compiled from the bearing load of the pin. In the deformability test, the extrusions without offsetting were shorter than the ones with 2mm offset. However, the forming pressure without offsetting was higher than the pressure with 2mm offset. Surface sink of the product without offsetting was observed below the tool probe. This implies that the probe restricts supplement of material volume to the die cavity directly below it, though it effectively extends the deformable material volume.