Ultrasonic Assisted Incremental Equal Angular Channel Pressing Process of AA 6063

Abstract

Recent technological developments need lightweight materials with high mechanical properties, especially in energy, automotive, and aerospace industries. [1,2] New chemical compositions have been developed with the increased demand for Al and their alloys. Moreover, to increase their mechanical properties, thermomechanical processes, such as extrusion, upsetting, and wire drawing, have widely been used for industrial applications of Al and its alloys. Severe plastic deformation (SPD) is one of the thermomechanical processes, which increases dislocation density. This increase results in finer grain sizes and increased mechanical properties, which render SPD techniques an attractive method. [3,4] Conventional methods, such as extrusion or upset forging, are able to deform, generally, external parts of materials. However, SPD methods, such as equal channel angular pressing (ECAP), can produce more homogenous strain distribution along the cross section of the material due to homogenous severe deformation. SPD methods are capable of doubling the mechanical strength while manufacturing ultrafine grain structures with mean grain sizes smaller than 400 nm. [4-6] Despite improved material properties' results of SPD techniques, most of them are still being used at the laboratory scale due to their manufacturing costs and usage difficulties. Materials size and length are the usage difficulties, which is generally restricted by die sizes. According to the literature, the ECAP is more convenient for producing longer specimens than other SPD methods for producing longer size ultrafine-grained materials. [7,8] However, this technique restricts the specimen length with its die size and plunger length, which is a significant limitation. High friction rate between the die walls and the specimen is another restriction for specimen size. Movable side walls during ECAP are developed as a solution to friction. However, the specimen length is limited to the die size. [9] Conform methods adapt continuous material feeding to SPD processes, which allow manufacturing fine-grained longer products. The conform SPD application was developed by Raab et al. in 2004 [10] for deformation of pure Al with ECAP. Various materials were used in conform methods, such as Ti G4, [11] TiNi, [12] Al6061, [13] and Al6101. [14] The most significant limitation of this method is the high friction rate between die and material. Especially, materials with low melting temperatures are effected from friction heat and result with a grain recovery that also decreases process efficiency. In the incremental ECAP (I-ECAP) process, which was first described in 2007, the material is fed step by step, and a punch deforms material between these steps; there are two separated synchronous movements of punch (deformation) and feeding system. [15] Thus, there is not a load on the specimen during feeding, which also eliminates high friction rates between die and specimen in contrast with traditional ECAP. Because of the continuous feeding of materials in the I-ECAP method, the ...

A novel equal channel angular pressing design to eliminate punch deflection and to reduce the pressing force

“…Friction also increases the required energy and carbon dioxide emission by increasing the required pressing force [15]. Ultrasonic assisted equal channel angular pressing is one of the practical approaches to reduce the pressing force in equal channel angular pressing process [16,17]. Finite element simulation was used in literature to study the effect of friction on equal channel angular pressing process [18].…”